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The work was con- ducted under the general supervision of Joseph F. Herrick, Jr., investigations leader, Horticultural Crops, Handling and Facilities Research Branch, Trans- portation and Facilities Research Division, Agricultural Research Service. Special acknowledgment is gue Kenneth L. Olsen and Charles F. Pierson for their review and helpful suggestions of the manuscript material pertaining to the work of the Market Quality Research Division, Agricultural Research Service, U.S. Department of Agriculture. Trade names are used in this publication solely to provide specific in- formation. Mention of a trade name does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture or an endorsement by the Department over other products not mentioned. II This publication reports research involving pesticides. It does not contain recommendations for their use, nor does it imply that the uses discussed here have been registered. All uses of pesticides must be registered by appropriate State and/or Federal agencies before they can be recommended. CAUTION: Pesticides can be injurious to humans, domestic animals, de- sirable plants, and fish or other wildlife—if they are not handled or applied properly. Use all pesticides selectively and carefully. Follow recommended prac- tices for the disposal of surplus pestic°*-- ~~d pesticide containers. Reece eee, ssasaaas Uae Postiti SYfeby FOLLOW THE LABEL US. DEPARTMENT OF AGRICULTURE Respiration and ripening processes _____ Storage temperatures _______--________ Humidity, moisture loss, and waxing ____ Air circulation and ventilation _________ FATES DUT NCAUION yes ee ree Controlled-atmosphere, or gas, storage _ Storage sanitation ~-_--___----------__- ZOMG ew re eee ee eee F152) 0) C= ep ae pre e | eh 9 of se eigen epee a ee Cold-storage plants and equipment __________ Refrigeration, 2222s a ee Cold-storage rooms ____-___-____-__ Required capacity of refrigeration system Caleulating refrigeration requirements __ Contents Page CVA AAAAENNN ES Cold-storage design _______________----_-_--- Precooling 222 2- = oan ee ee Capacity and height of rooms _____-____~ Layout: of rooms: 2252-222. -<5-- 55 sk Mansand, ducts) £2225 ot Planning for economy ____------_-_____ balety. 225.2 Cold-storage management and plant operation _ Handling the fruit _____-_______________ Control of the plant _______-_-_________ Operating efficiency -__________________ Literature cited __________________________- AD DONnGIx: 22.022 8h ee eee Se How to make a thermocouple ______-____ Inexpensive paint for concrete walls _____ Harvesting maturity of apples __________ Pressure testing _-_____________________ Harvest maturity for pears ____________ This publication updates and supersedes Department Circular No. 740, “Cold Storage of Apples and Pears.” Washington, D.C. Issued December 1971 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 — Price 55 cents Stock number 0100-1373 Wil alla MOAI AN 10. TO 21. 22. List of Tables Rates of evolution of heat by fresh fruits when stored at various temperatures _______________ Recommended storage temperature, relative humidity, and freezing temperature of fresh fruit ___ Calculated condensation per 1,000 B.t.u. on cooling surfaces from air at 32° F. _--___________ Oxygen, carbon dioxide, and temperature requirements for controlled atmosphere storage of se- lected’ varieties .0f ‘apples: So = me Se es a ee eee Capacity and power data for typical 2-cylinder ammonia compressors _________________________ Relation of coil-room temperatures to relative humidity in storage room _______-_________ Data on sodium chloride (NaCl) and calcium chloride (CaCl) brines ______________-____- Relative humidity of atmosphere by wet- and dry-bulb thermometers __________-__-__-_-_-__»_ Relation of head or condensing and suction pressures to horsepower requirements per ton for typi- Cal ‘ammonia: Compressors)... 2 === a ee ee Flesh-firmness recommendations for harvesting pear varieties _.-________-_- List of Figures Section through water trap with the water seal indicated ___ ______________________---_---~- Essential parts of a compression refrigeration system —_________________________-__-_-_____- Effect of condensing and suction pressures upon power requirements of a typical ammonia com- PECSSOR cn a a a a a a Effect of condensing and suction pressures upon the capacity of a typical ammonia compressor __ Rear ‘view ota: three-fan: unit cooler: 2.22.2... 2-34 2 ee Looking up at unit coolers, pipes, and catwalk located overhead in center of cold-storage room __~ Thermocouple equipment for reading fruit temperatures at remote parts of cold-storage rooms. The wires may be installed for reading temperatures at a central point or the reading instrument may be carried from room to room. Caution should be used as some instruments do not read accurately when the ambient temperature is less than 45° F, _-_-_--_-__-__-_-_--_ Curved vanes or splitter inside a rectangular duct ~________________________-__---- Looking down on a small section of the splitters shown in figure 8 ____________________________ Closed: reversing’ dampers: in-a large air duct. 22. + .-- eee Open reversing dampers in a large air duct _-________________________-___-_ Automatic reversing mechanism for dampers shown in figures 10 and 11 _____-_--__-_______ View of air deflector inside a rectangular duct, directing air out through a slot in the top of the ch) ee ee a ee iA ee ea Oe oe Aree esse be cc eee A Diagram of delivery and return ducts that may be used interchangeably with a reverse air system. Deflector vanes are used to equalize the quantity of air delivered from the varisized duct open- ings. As the distance from the fan room increases, these openings are made larger to equalize the flow of returning air. The number of openings is adjusted to the length of the duct ______ Normal storage life expectancy of Delicious apples when cooled at different rates and stored at different temperatures. For each week of exposure at 70° F. before storage, deduct 9 weeks of storage life at 32° F.; for each week’s delay at 58°, deduct 1 month of storage life at 32° ___ Lines painted on floor will facilitate placing pallet loads or pallet boxes of fruit and help in pro- viding uniform spaces for the movement of cold air through the stored fruit _---______________ View showing side rails along wall to prevent stacking of fruit too close to wall and preventing Alf CITCUIATION: = 222222 e3s5s ee ee Se ce nS Pallet load of fiberboard boxes of fruit spaced when 1- by 4-inch boards placed on end and other pallet loads with 1- by 4-inch corner boards to take load of pallet above __--_-__-__-__-__- Recording thermometers are useful for giving temperature fluctuations and providing a permanent file on cold-storage performance _________________-_-..---------------------------+--_______ Psychrometers consisting of wet- and dry-bulb thermometers that can be used for determining relative humidity of storage rooms: A, Sling type; B, wall type; and C, hand-aspirated type Arrangement of multiple compressors in engine room ______________-_-_-__-_-_- = Apparatus for fusing thermocouple junctions ________________________-__-_- IV Page 38 40 41 41 42 43 44 47 50 STORAGE FOR APPLES AND PEARS’ By GLENN O. PATCHEN, mechanical engineer, Transportation and Facilities Research Division, Agricultural Research Service INTRODUCTION Holding apples and pears in cold storage in producing areas rather than at market ter- minals or at points in transit has become a com- mon practice. In the Pacific Northwest this change has been more or less coincident with the decline of speculative buying of the fruit by eastern interests and with the growth of cooperative marketing enterprises owned and controlled by the growers. As a result, the available cold-storage space in the fruit-grow- ing districts in Washington and Oregon has been materially increased,? but even yet it is inadequate for the needs of the industry. Many of the existing cold-storage plants are in- adequately equipped to handle satisfactorily the tonnage stored. Year by year existing plants are remodeled and expanded and new plants are built to provide additional refrigerated storage space. The construction of new con- trolled atmosphere storages has_ increased greatly in the last 4 or 5 years. Some of the storages are well designed and carefully and efficiently operated. _ The purpose of this publication is to present | in concise language, as nontechnically as possi- ble, the essential features in the design and operation of cold-storage plants and in the handling of the stored fruit in the Pacific Northwest, although the same principles will 1The previous publication, Cold Storage of Apples and Pears, published February 1946, was written by W. V. Hukill and Edwin Smith, both of whom have retired. * Total gross refrigerated warehouse space in Wash- ington and Oregon increased from 109 million cu. ft. in 1951 to 231 million cu. ft. in 1967 alone. (Agricultural | Statistics 1969 and 1952.) be found equally useful in other parts of the country. The principal fruits requiring refrigeration for extended storage are apples and pears. Grapes also are stored extensively in some places, particularly in California. Refrigeration is used also for the precooling or short-time storage of other fruits, such as cherries, plums, and apricots. Rural electrification and automatic refrigera- tion equipment are now universal, and indi- vidual fruit growers or small groups of grow- ers have been building cold-storage plants at or near their orchards instead of relying on large plants that serve a whole community or a large number of growers. This has been coincident with the development of better handling and packing methods. The handling methods, transportation equipment, and facili- ties required for sorting and packing extended the distance that apples can be moved from orchard to the cold-storage house so that pack- ing and shipping will not be under the pressure of getting the job done in a matter of a few days after picking. Having refrigeration facili- ties at hand has permitted the orchardist to give his fruit optimum protection while it is awaiting packing and to employ a compara- tively small crew of skilled harvesters instead of having to mobilize large crews. This has prevented fruit from wasting and allowed it to be handled economically in large volume. Many of the cold-storage plants designed and operated along lines found satisfactory for general cold storage have been neither efficient nor economical for fruit, owing to specialized 1 2 MARKETING RESEARCH REPORT NO. 924, U.S. DEPARTMENT OF AGRICULTURE requirements for the rapid cooling of the fruit and the maintenance of its temperature within narrow limits. For best possible returns on in- vestments, emphasis must be placed upon both the design and the efficient operation of a fruit cold-storage plant. Many cold-storage operators, including fore- men and plant engineers, will desire more detailed information on many subjects that nec- essarily are greatly condensed in a publication of this kind. For this reason, attention is called | to other publications on refrigeration engineer- ing and fruit storage listed under Literature Cited (p. 48). RESPONSE OF FRUIT TO STORAGE CONDITIONS Before undertaking to design and operate a cold-storage plant, the nature of the product to be stored must be understood. Apples and pears are alive at the time of harvest; the length of time they may be held for consumption in the fresh state depends upon how long the end of their life can be delayed. Their storage life be- gins the day they are picked, even though they may remain temporarily in the orchard or packinghouse. The length of storage life varies with the variety, orchard, district, and condi- tions of growth, the stage of maturity at which the fruit is picked, and the temperature and humidity at which it is held. For additional discussion on these subjects, see reference (32) 2 Respiration and Ripening Processes An apple or pear consists largely of water and contains sugars, fruit acids, and, in and between the cell walls, pectin. The pectins cement the cells together, and the degree of adhesion or disintegration of the cells de- termines whether the flesh of a fruit is firm, tough, crisp, and juicy, or soft and mealy. The chemical changes that take place in fruit dur- ing ripening are very complex. Starch changes to sugar; acids and insoluble pectins decrease; and volatile constituents are given off. These changes go on until the fruit becomes overripe and unpalatable, with subsequent collapse. Dur- ing the ripening process, oxygen is consumed from the air, water and carbon dioxide are produced, and heat is generated. All these ac- tivities are embodied in what is spoken of as respiration. The chemical changes taking place in ripen- *TItalic numbers in parentheses refer to Literature cited, p. 48. ing fruit, and consequently the rate of respi- | ration, are retarded as the temperature is. lowered. The quicker heat is removed from fruit after picking to bring it to an optimum storage temperature, the earlier the ripening. processes will be retarded and the longer the. fruit can be kept. | The generation of heat during the respira-. tion and ripening processes (referred to in more | detail on p. 28) is greater than is commonly > realized and deserves important consideration . in the design and operation of fruit cold-_ storage houses. The faster a fruit ripens, the greater the quantity of heat generated. A Bart- lett pear ripens faster than an apple at a given | temperature, and, therefore, its greater heat of respiration results in larger refrigeration | demands, even when it is taken into storage at. the same temperature as the apple (table 1). Storage Temperatures Research by Magness and others (17) has: shown that when apples are stored at 30° F.! about 25 percent longer time is required for them to ripen than at 52°. When stored at 40°, | the rate of ripening is about double that at 32°. At 60° the rate is about three times that at’ 40°, and at 85° the softening and respiration rates have been found to be about double those at 60°. These findings emphasize the im- portance of having the cold storage designed to quickly establish and maintain uniform low | temperatures. A study on the effect of hydro-. cooling apples (Red Delicious, Golden Delicious, and Winesap apples) “Indicates that for long storage of apples, hydrocooling offers no ad-| vantages over air-cooling in cold storage rooms, providing the cooling to approximately 32° is accomplished within a week. If there is in-| Se eee ee ee eee ee ee ee ho TABLE 1.—Rates of evolution of heat by fresh fruits when stored at various temperatures 1 British thermal units (B.t.u.) per ton per day at indicated temperature Kind of fruit 32° EF. 40° to 41° F. 59° to 60 ° F. 68° to 70° F. 77° to 80° F. PD DOS see or se 500-900 1,100-1,600 3,000-6,800 3,700-7,700 ____________ Apricots __---_-_------__ ___------- 1,800-8,300 8,300-15,100 13,200-27,500 Se Cherries, sour ___---_-_ 1,300—2,900 2,800—2,900 6,000-11,000 8,600-11,000 11,700-15,600 Cherries, sweet ___-______ 900-1,200 2,100-3,100 5,500-9,900 6,200-7,000 Peaches _________________ 900-1,400 1,400-2,000 7,300-9,300 13,000-—22,500 17,900-26,800 Pears, Bartlett _.._______ 700-1,500 1,100-2,200 3,300-13,200 6,600-15,400 Pears, Kieffer —____-____~ 400-500 2,400-5,300 3,400-6,100 4,300-6,300 Condensed from Lutz and Hardenburg (15). sufficient refrigeration capacity in a warehouse and a number of storage units are involved, hydrocooling might be advisable” (28). Uniformity of Temperature Uniformity of temperature relates both to its range on the thermometer scale and to the maintenance of.a like temperature throughout a storage room. In some plants, cycles of com- pressor operation cause a fluctuation of 2° to 4° F. in air temperatures. Slight fluctuation does not injure fruit unless it is downward to a point resulting in freezing or in low-tempera- ture injury. Apples or pears exposed to a tem- perature fluctuating from 30° to 32° will keep as long as if stored at a constant temperature of 32°. If the fruit is stored at a uniform tem- perature of 30°, however, its life may be lengthened by 25 percent (17). Maintaining uniformity of temperature in all parts of a storage room is more important than avoiding small fluctuations at a given point. Marked variation in temperature within the storage room will bring about different rates of fruit ripening. This frequently results in mixing overripe and prime fruit in ship- ment, or it may result in undetected deteriora- tion and decay of fruit in inaccessible locations. Thermometers and Uniform Temperatures Because fruit is a living matter, it is generat- ing a small quantity of heat continuously. The air circulation is not uniform in all parts of the storage room, therefore, the fruit tempera- ture will not be the same at all locations. The heat generated must be given up to the air to prevent a rise in fruit temperature. For this reason, it is not possible to have the same air or fruit temperature in all parts of a storage room. In some storage rooms, the temperature variation may be only a fraction of a degree, while in others it may vary several degrees even after the fruit has been cooled to its final temperature. Because of these variations in temperature, readings from thermometers placed in the aisles may be misleading. To operate a plant to the best advantage, the highest and lowest fruit temperature in each room should be known. Since the fruit stored in packed boxes may be one degree or more higher than the circulating air the core temperature must be known. This temperature determines how well the fruit will keep. The use of thermometers to take temperature readings of the fruit in all parts of the storage room after it has been filled with fruit is difficult. There are times during the season, as fruit is shifted or loaded out, when it is possible to take core temperatures. Often, if temperature conditions are known, steps can be taken to make them more uniform. When fruit-tempera- ture readings are not taken, temperatures shown on the thermometer in an aisle are frequently assumed to prevail throughout the room. This is not true, and wide temperature variations may occur, especially for the first few weeks of storage. (See the discussion on use of thermocouples for reading temperatures in these inaccessible places, p. 26.) 4 MARKETING RESEARCH REPORT NO. 924, U.S. DEPARTMENT OF AGRICULTURE The influence of the temperature of fruit on the rate of ripening has special significance in cold-storage management. Apples at 70° F. ripen as much in 1 day as they would at 30° in 10 days; a delay of 3 days in an orchard or in a warm-packing shed may shorten their stor- age life as much as 30 days, even if they are then stored at 30°. Storage temperatures recommended for various fruits are shown in table 2. Effects of Rapid Cooling Apples and pears are not injured by rapid cooling if the surface temperature of the fruit stays above freezing or the fruit is not of a variety susceptible to injury by low tempera- ture occurring above the freezing point. Some low-temperature injuries of apples are dis- cussed on pages 39 to 42. TABLE 2.—Recommended storage temperature, Freezing in Storage Because of the dissolved constituents fruits and _ vegetables acids), the freezing points of these products are appreciably below that of water. The aver- age freezing point of apples is 28.4° F. It ranges from as high as 29.7° to as low as 27.3° in some of the summer varieties, but it is be- tween 28.0° and 29.0° for the principal winter varieties that are stored. The freezing tempera- | tures of pears are slightly below those of ap- ples. Average freezing temperatures of some fruits are given in table 2. Lutz and Harden- burg (15) and Whiteman (36) have more complete information on this subject. Humidity, Moisture Loss, and Waxing The loss of moisture from apples and pears | in storage, resulting in shriveling or wilting, is relative humidity, and freezing temperature | of fresh fruit} Kind and variety Storage Relative of fruit temperature humidity °F. Percent Apples: Delicious ______________ 30-32 85-90 Golden Delicious _______ 30-32 85-90 Jonathan _____________- 35-36 85-90 Winesap ______________ 30-32 85-90 McIntosh ______________ ° 36-38 85-90 Yellow Newtown _______ ® 38-40 85-90 Pears: Bartlett __._____________ 29-31 90-95 Anjou __----_---___ 29-31 90-95 Peaches: 31-32 90 Apricots: 31-32 90 Cherries: Sour ___------- 32 90-95 Sweet _____________ 30-31 90-95 * Condensed from (15). Freezing Approx. length Specific heat temperature of storage period °F. B.t.u./lb./° F. 28.4-29.3 4-8 months 0.87 28.4—29.3 ?4-8 months 87 28.3-29.3 3-6 months 87 28.2-29.0 5-8 months 87 28.4-29.3 4-8 months 87 28.0-29.3 5-8 months 87 * 27.8-29.2 5214-3 months 86 26.9-29.2 °4-6 months 86 29.6—30.3 2-4 weeks 91 30.1 1-3 weeks 88 28.0-29.0 2-7 days 84 24,1-28.0 2-3 weeks 87 ? Polyethylene liners are needed for maximum storage of Golden Delicious. * McIntosh and Yellow Newtown apples may develop brown core during extended storage at 32° F.; hence, they | should be stored at the higher temperatures. “Whiteman, T. M. (36) found in his research that the highest points of 11 varieties of pears ranged from 26.7° to 29.2° F. He also states, “In general, the average freezing points decreased as the soluble solids increased, but there was no consistent relation between these factors.” * For long storage, pears should be packed with polyethylene liners. in| (chiefly sugars and | directly related to moisture in the form of wa- ter vapor in the storage atmosphere. When the relative humidity is maintained at above 90 percent, fruit rot is encouraged as well as sur- 'face-mold growth on the fruit and on the walls, ‘ceilings, and floors of the storage room and on the packages. Apples and pears may be kept in ‘cold-storage rooms without risk of excessive moisture loss with active air movement, under ideal conditions of humidity. When the relative humidity is low, shriveling is aggravated by ‘moving air, particularly when the fruit is stored without wraps. A relative humidity of 85 percent is considered ideal for most fruits. ‘Some storages are using a higher relative hu- midity, but higher humidities in cold storages are conducive to mold growth. _ High-cost cooling surfaces and their acces- sories are necessary to maintain 90-percent ‘relative humidity at full refrigeration load. To maintain a 95-percent relative humidity by cooling surface design is virtually prohibitive. ‘Table 3 shows the difficulty in controlling hu- midity by coil surface alone. One way of reducing condensation is by re- ducing the temperature difference between the cooling surface and the air (table 3). This may be done by improving liquid feed, regulating back pressure, having better defrosting, using clean evaporator coils, having higher air velocity through the coils, and having larger coil surfaces. Such reduced temperature differ- ence is very effective in reducing condensation at low humidities. _ Table 3 also shows that when the air is at 90-percent relative humidity, lowering the tem- perature difference from 20° to 4° F. reduced condensation by only one-third. At 95-percent relative humidity, the same reduction in tem- perature difference increased condensation. At ‘this relative humidity, a 1° difference is neces- sary to substantially reduce condensation. _ The principal value of polyethylene film box liners for apples is the reduction of moisture loss and shriveling (29). Dehydration is very ‘noticeable when appies have little natural wax and the relative humidity of the storage room is below 85 percent. Perforated polyethylene liners are used extensively for Golden Delicious apples. STORAGE FOR APPLES AND PEARS 5 TABLE 38.—Calculated condensation per 1,000 B.t.u. on cooling surfaces from air at 32° FA Temperature (°F.) difference between coil Relati araiity surface and air at 32° F. (percent) 1° 2 4° 10° 20° Pounds Pounds Pounds Pounds Pounds 100___ 0.35 0.36 0.36 0.33 0.31 95___ 11 31 .34 .o2 31 90_-- ___ fae 19 .28 28 80_-- ___ aoe a 18 23 (( dais Bete .02 18 60_-_ ___ 7 —_ = 14 1 Developed from a discussion on humidity control by Guillou and Richardson, University of California, Davis, Calif. Pears get the full benefit of polyethylene liners only when they are sealed (29). The fruit should be washed with an effective fungicide before being packed as the high relative hu- midity inside the liner may accelerate the growth of decay organisms. The liners should be opened to allow ventila- tion when the pears are removed from cold storage for ripening. The use of polyethylene pallet box covers over nonprecooled apples and pears is not advisable as cooling is retarded and the fruit ripens faster (12). Waxing fruit has generally been adopted in the Pacific Northwest. Schomer and Pierson (30) have the following to say on waxing: Commercial waxing is not sufficient protec- tion against moisture loss to replace the “poly” liner for storage of Golden Delicious apples and Anjou pears. Application of sufficient wax to prevent shriveling would cause physiolog- ical damage. Consequently, the reduction of moisture loss due to waxing is relatively unim- portant, especially since the fruits most susceptible to wilting still must be packed in “poly” liners which reduce moisture loss to an insignificant amount. Waxing enhances the appearance of apples and pears by imparting a shine which persists even after extended storage. There was no enhancement of quality or ex- tension of storage life as a result of waxing [on apples]. Wax on pears retards ripening and might extend shelf life. Because of the effect of wax on ripening, however, the amount applied must be controlled carefully. 6 MARKETING RESEARCH REPORT NO. 924, U.S. DEPARTMENT OF AGRICULTURE Air Circulation and Ventilation Apples and pears should be stored in an atmosphere free from pronounced odors. They acquire off-flavors when stored with potatoes, onions, cabbage, and certain other products. If stored by themselves, most fruits do not re- quire a change of the air other than that oc- casioned by the opening of doors or ports under normal operation, provided the fruit is not overripe when received and is quickly cooled to an optimum storage temperature. In most parts of the United States, sub- stituting natural cold air for mechanical refrig- eration during winter months is not practical; therefore, it is seldom advisable to make any special provisions in the storage designs for bringing in outside air. In the storage of apples an active air move- ment about the packages is advantageous, par- ticularly with varieties susceptible to apple scald. Less scald develops when they are stored in moving air. A heavy odor in an apple storage means that some of the fruit is reaching an advanced stage of ripeness, and the storage period should be terminated. Ethylene, a gas given off by ripening apples, pears, and some other fruits, hastens the ripen- ing of fruit stored at high temperatures but has very little effect at low temperatures. Even a very small quantity of the gas will cause accelerated ripening at favorable temperatures. This is an added reason for designing the cold storage for the rapid cooling of fruit in all parts of the rooms rather than providing for removing ethylene by ventilation. Air Purification In some closed cold storages, air purification becomes a necessity to prevent the fruit from taking on an objectional flavor or odor. Acti- vated coconut shell carbon units have been used extensively for this. Smock (31) says the main function of an air purification unit is to keep down foul odors in the room. Experiments with activated carbon as an air purifier by Gerhardt (8) showed that activated carbon did not lower ethylene gas concentration in storage rooms. According to the findings of Gerhardt and Siegelman (11), the ripening effect of ethylene - gas on stored apples and pears at 31° F. is of | little consequence, but it does accelerate ripen- ing at elevated temperatures. Some credit was | given to the prevention of scald on fruit by the | use of activated carbon filter, but according to recent developments in the use of diphenyla- | mine (22) for the prevention of scald, the use | of carbon filter for this purpose alone would | not be justifiable. When activated charcoal has | reached its practical saturation in service, it must be reactivated, usually at the manu-— facturer’s plant (7). Gerhardt and Sainsbury (10) experimented with brominated carbon for absorbing volatiles from the air of the storage room. He found that brominated carbon was a more efficient absorbent of ethylene than was activated carbon but both were about the same when it came to removing volatiles other than | ethylene. Brominated carbon is very corrosive | on metalic containers so it is not used. Controlled-Atmosphere, or Gas, Storage Reducing the oxygen content and increasing the carbon dioxide in the atmosphere of a stor- | age room slows down the respiration, softening, and ripening process of apples and pears. Controlled-atmosphere (C.A.) storage has the greatest advantage for apple varieties that | may be injured at low-storage temperatures of 30° to 31° F., such as McIntosh, Jonathan, and Yellow Newtown varieties. The use of C.A. storage for Delicious and — Golden Delicious apples has expanded very rapidly in the Pacific Northwest. A law in Washington State requires that apples labeled as C.A. fruit must meet export standards at time of shipment. This law has resulted in a price advantage for C.A. stored fruit. Several methods are used in obtaining a C.A. | storage room. The oldest method practiced is to seal the storage room until it is essentially gas proof with a sheet metal lining or high-density plywood and caulked joints. The fruit then consumes the oxygen until it reaches the de- sired level, thereafter the concentration of the gas is controlled by permitting outside air to. enter the room. The concentration of carbon } dioxide is built up by fruit respiration; to limit | STORAGE FOR APPLES AND PEARS 7 this concentration level, the room atmosphere is circulated through an atmospheric washer containing a dilute solution of caustic soda (NaOH) to absorb the excess carbon dioxide. Refrigeration equipment also is necessary since the fruit must be held at its normal cold stor- _ age temperature. Van Doren (34) states that, ‘The concentra- tion of the solution of (NaOH) should not ex- ceed 5 percent of caustic sodium hydroxide and operators who use the flake caustic soda should not exceed 14 pound of the caustic soda per gallon of water in the scrubbing solution. Lower concentrations are to be desired, with | only enough caustic soda being put in the water to keep the increase of CO. removed from the | storage air.” Van Doren (34) further states, “Tt is wise to plan on having about one pound of caustic [soda] per bushel of apples stored, although most operators will use only about 14 _ pound per bushel per season.” _ The use of dry-lime scrubbers is becoming popular for C.A. storage rooms because of the scrubber’s simplicity, efficiency, and economy. Sacks of dry-hydrated lime are placed directly in the room or adjoining room and the room air circulated by the sacks of lime. The lime ab- -sorbs the carbon dioxide (CO.) from the air. When the CO. concentration of the room air begins to increase, these sacks are removed and replaced with fresh sacks. Some operators use atmospheric equipment in conjunction with the _ dry-hydrated lime. This machine generates the desired atmosphere outside the storage room and delivers it into the room at a designated _ pressure of about 1 inch of water. By doing this the rooms do not have to be so airtight and plastic air bags, or breather bags, are not used to take care of changes in atmospheric pressure. Usually a small water seal trap with a 14-inch water seal is provided for any unfor- . seen large variation in pressure (fig. 1). The CO, may also be scrubbed from the air of the storage room with water. Glycol is added - to the water to prevent it from freezing. The water or brine flows over cells inside the stor- age room where the room air is blown through it. The brine cools the air as well as absorbs the CO.. The brine is then pumped (or flows by gravity) from the room and discharged 4” TUBING WATER SEAL OUTSIDE ROOM INSIDE ROOM FIGURE 1.—Section through water trap with the water seal indicated. over cooling coils where it is chilled to the desired storage temperature at the same time being aerated, and the excess CO. is given off to the outside air. Some trouble has been experienced when this method is used. The brine may give off oxygen to the room air, raising the oxygen level above the level desired. Operators have reported that when a defoaming agent was added to the water the increase of oxygen in the storage room air stopped. To keep the air temperature in the room from fluctuating too widely, a volume of air of approximately 1 cubic foot per minute per box of apples stored should be used. A large volume of brine should also be circulated. By using this method relative humidities of 95 percent can be obtained easily. When the air velocity is increased, high hu- midities will prevent weight loss from the stored product. A commercial external gas gen- erator can also be used with this method. Where the oxygen level in a controlled at- mosphere room is dependent upon the stored fruit, the room must be tightly sealed. The use of external generators to supply the desired oxygen level of air to the room allows some tolerance in the sealing. The amount of air leakage is fixed by the size of the room and type of generator used. Generally, some auxiliary method must be used in C.A. rooms to produce a high relative humidity of 90 to 95 percent. Usually water is sprayed directly into the air of the room. In some storages where a commercial gen- erator is not available, the room atmosphere can be obtained by flushing the rooms with 8 MARKETING RESEARCH REPORT NO. 924, U.S. DEPARTMENT OF AGRICULTURE nitrogen. This method is expensive and should be used only in bringing the room atmosphere to the desired composition when natural ab- sorption of the oxygen from the room air by the fruit is not fast enough. The oxygen content in air of a C.A. room will not support human life. Therefore, an oxygen mask should be worn when entering such a room or the door to the room should be left open for several hours before entering. Someone should be outside the room as a safety man while a workman is in the room if the oxygen content is low. For further reference on C.A. rooms, see reference (15) and the _ references listed therein. Table 4 gives the recommended storage temperature and oxygen and carbon dioxide levels for C.A. storage of selected varieties of apples. Pears respond very well in C.A. storage but require a high relative humidity of at least 90 to 95 percent. Use of C.A. storage for pears has been slow, however, because of the excellent results obtained when pears are packed and stored with polyethylene-lined containers (15, 9). Storage Sanitation A storage interior free from decayed fruit, dirt, and mold is a criterion of good manage- ment. The growth of surface molds within a storage, however, may indicate favorable con- ditions of relative humidity and does not par- ticularly menace stored apples and pears packed in closed containers. The use of fun- gicidal paints or the annual whitewashing of walls, ceilings, posts, and air ducts and the oiling of the floors will largely prevent the growth of surface molds. Mold growth and spores may be killed by spraying the empty storage with a sodium hypochlorite solution having 0.8 percent available chlorine. The rooms should be closed for a few days after spraying. Chlorine vapor from a spray of sodium hypochlorite is an irritant to the mucous membrane. Workmen should therefore be protected from injury while spraying. This may be done either by using fans to produce an air movement to carry away the fumes or TABLE 4.—Oxygen, carbon dioxide, and tem- perature requirements for controlled atmos- phere storage of selected varieties of apples } Variety ee Oxgyen Temperature Percent Percent a ke Cortland? ________ 2-5 3 38 Delicious* ________ 1-2 2-3 30-32 Golden Delicious*__ 1-2 2-3 30-32 Jonathan _______ 3-5 3 32 McIntosh? ________ 2-5 3 38 Northern Spy _____ 2-3 3 32 Rome Beauty _____ 2-3 3 30-32 Stayman __ 2-3 3 30-32 Yellow Newtown __ 7-8 2-3 38-40 + Adapted from Lutz (15). *Cortland and McIntosh varieties are stored in 2 percent CO, the first month and 5 percent thereafter. °In Washington State, 1-3 percent oxygen is recom- mended for Delicious and Golden Delicious varieties, rather than 2-3 percent oxygen. by wearing an all-service gas mask in non- ventilated rooms. For further discussions on this topic, see (15). Ozone Ozone as used in cold storages is a deodorizer and a deterrent to surface molds which develop in high humidities. Although it is not too widely used in cold storages of apples and other fruits, a few commercial storages use it regularly. Ozone is a powerful oxidizing agent, and is used mainly to oxidize many objectional odors and gases that are associated with storages. It is made by the condensation of oxygen from the air with a high voltage current. At low concentrations, ozone has a pleasant odor, but prolonged exposure to concentrations above 0.1 part per million (p.p.m.) should be avoided. Schomer and McColloch (27) report that in their experiments ozone did not check decay of the fruit in storage, but air-borne spores were killed by continuous exposure to ozonized atmosphere, so that viable spores occurring naturally in the atmosphere were reduced to STORAGE FOR APPLES AND PEARS 9 an insignificant number. Mold on the surfaces of packages and walls of the storage room was prevented. Ozone did not reduce the scald enough to pro- vide a satisfactory control. Some varieties of apples develop lenticel injury due to prolonged storage in strong concentrations of ozone. In addition to injury of lenticel tissue, other serious effects of extended exposure to 3.25 p.p.m. of ozone may occur, such as the skin of the apple having a sticky and varnishlike ap- pearance. The flavor of some apples is also im- paired. The extent of this off-flavor varies with the variety. Schomer (27) also reports that ozone ap- peared to have no effect on major physiological activities of apples such as ripening during the storage period as measured by pressure tests, composition of internal atmosphere, pH, and total acidity. STORAGE BEHAVIOR OF APPLES AND PEARS Success in the storage of apples and pears is dependent upon consideration of their in- herent characteristics and upon their normal cold-storage life. The handling of the fruit be- fore storage is also important. “Maximum stor- age life can be obtained only by storage of high-quality commodities shortly after harvest” (15). Apples A temperature of 30° to 32° F. and a relative humidity of 85 to 88 percent give best results in the storage of most varieties of apples in most parts of the United States. Certain va- rieties, however, sometimes will not tolerate continuous low-temperature storage. Yellow Newtown, McIntosh, and Rhode Island Green- ing apples should be held at 35° to 38° to pre- vent development of internal browning and brown core. Grimes Golden should be held at 34° to 36° to prevent soggy breakdown. Under conditions described below, certain other varie- ties should be stored at temperatures higher than 32° to avoid storage disorders. The higher the storage temperature the faster the apples will ripen and the sooner the end of their storage period will be reached. Apples stored at distant points from markets must have sufficient life left when withdrawn from storage to withstand the higher tempera- tures of transportation and distribution. The longer apples are stored the shorter their life after removal to higher temperatures. Thus, when distribution requires 10 days to 2 weeks, apples that leave cold storage in apparently good condition may reach the consumer over- ripened and mealy with many decayed fruits. Some forms of deterioration of apples in stor- age are discussed here. Ammonia Injury Ammonia injury on apples is recognized by a prominence of the lenticels, which become white at the center, with some or many of them surrounded by bands of black on the red sur- faces or of green on the yellow-green surfaces. Even short exposures to small concentrations of ammonia will produce these color changes. When ammonia concentrations are 2 to 5 per- cent, an exposure of 5 to 8 minutes results in prominent lenticels with the surrounding dis- coloration spreading between the black or green rings. After the apples have been exposed to the fumes for a short period, they partially recover when aerated. The residual damage may be only a slight skin blemish around the lenticels or it may be more serious and affect the flesh tissue. Apples Rots Apple rots are caused by fungi commonly referred to as molds (7, 25). From the stand- point of the cold-storage operator, a most im- portant characteristic of rot-producing fungi is that their growth and the germination of spores are either entirely stopped or greatly held in check at temperatures of 30° to 32° F. The riper the apples are before being handled, the more susceptible they become to injury and rot infection. The growth of such important fungi as blue mold, gray mold, and Alternaria progresses slowly at temperatures of 30° to 32° once infection takes place. Gradual cooling 10 MARKETING RESEARCH REPORT NO. 924, U.S. DEPARTMENT OF AGRICULTURE over 2 to 4 weeks is a bad practice. It hastens the unseen development of rot fungi and later results in a greater percentage of decay than in fruit cooled quickly. The cold-storage warehouseman needs to keep a close watch for ripening and decay in all storage lots. Certain “side rots” and the “SDull’s-eye” rot from perennial canker grow slowly until apples reach a certain stage of ripeness, whereupon these rots grow rapidly and become apparent in a few weeks, often causing severe loss before being detected. Susceptible lots should be inspected frequently and should be sold before becoming ripe, es- pecially after the first signs of decay are noticed. The effect of cold storage upon susceptibility to decay of the fruit before it is washed and packed depends upon the character of storage and the degree of ripeness of the fruit when handled. Firm apples of good quality should be placed in cold storage immediately after har- vest. They should be cooled to a core tempera- ture of 32° F. within 1 week. When apples are treated this way the danger from storage rot is decreased. This allows the packing season to be extended. When apples are to be held at temperatures conducive to ripening, it is pref- erable to pack them before storage and market them as soon as possible. Bitter Pit Bitter pit, sometimes called Baldwin spot or stippen and recognized by sunken areas or pits with brown spongy areas in the flesh, cannot be controlled in cold storage. Bitter pit is a disorder related to growing conditions and may become noticeable on the tree or after the fruit has been harvested and stored. Crops of suscep- tible apples intended for storage should be held at 30° to 32° F. for 2 months before being packed so that affected fruits may be sorted out. Internal Browning, or Brown Core The terms “internal browning” and “brown core” are used, respectively, to designate the effects of low-temperature injury in Yellow Newtown and McIntosh apples. The Yellow Newtown grown in the Pajaro Valley in Cali- fornia is especially susceptible, and in this variety the injury commonly appears as elongated areas of brown discoloration radiat- ing from the core. As it progresses, it may spread throughout the tissue and resemble internal breakdown. In McIntosh, as well as in Yellow Newtown and some other varieties, it is characterized at first by a slight brown dis- coloration between the seed cavities that may later progress until the entire core area be- comes brown, making the fruit unmarketable. Susceptible apples should not be stored at 30° to 32° F. but at 36° to 40° to prevent or mini- mize losses during storage. In districts where internal browning and brown core are serious storage hazards, the application of C.A. storage should be considered. Internal Breakdown Internal breakdown, recognized by a more or less general brownish discoloration of the flesh, usually outside the core and at the blossom end of the apple, is essentially death from old age. It manifests itself in various ways in different varieties. In Jonathan, an area on one side or in a zone beneath the skin may become brown and dry while the rest of the flesh is crisp and juicy. This is sometimes spoken of as “Jonathan breakdown.” It is associated with fruit har- vested at an advanced stage of maturity. It may occur early in the storage season. In other varieties, internal breakdown may appear as brownish streaks in ripe, mealy tis- sue, later becoming badly discolored, dry, and spongy. This is designated as “‘mealy break- down,” and in some varieties the skin often ruptures. Late in the storage season or after removal from storage, this disorder frequently occurs beneath bad bruises, or in tissue near the core in a region affected with severe water core at the time of harvest. The risk of loss from internal breakdown is negligible when apples are harvested at the proper stage of maturity and stored promptly at 30° to 32° F. for normal periods for the variety. When found in a storage lot, it should be regarded as a sig- nal for prompt disposal of the fruit. A somewhat similar type of discoloration occurs in the fruit of some varieties in some districts before harvest. It is caused by a de- STORAGE FOR APPLES AND PEARS im! ficiency of boron. This type of breakdown does not become worse while the fruit is in storage. Storage Scald Storage scald is a browning of the skin and is distinguished from soft scald by being super- ficial, generally diffuse, and more pronounced on the green or unblushed surfaces. It is as- sociated with fruit harvested at an immature stage. Storage scald may be entirely prevented in some varieties, including Delicious, by delay- ing picking until the fruit is sufficiently ma- ture. It is thought to be induced by certain volatile products of ripening. If apples are not too immature when harvested, storage scald can be largely controlled by placing paper con- taining at least 15 percent of an odorless and tasteless mineral oil in contact with the fruit as soon as possible after harvest. The present treatment for storage scald is the use of Diphenylamine (DPA) or ethoxyquin (Stop Scald). DPA is available in wettable powder, emulsifiable liquids, or in impregnated wraps (22, 23). Pierson (22) states, A concentration of 2,000 ppm should be used for Delicious and Winesap apples, and 1,000 ppm for Rome Beauty apples. The impreg- nated wraps can be used on all of the above varieties. DPA should not be used on Golden Delicious apples. Ethoxyquin emulsions or wraps should be used on this variety. Timing of application is important. De- licious should be treated as soon after harvest as possible, preferably with a delay of less than 10 days. For Winesaps a delay of 4-6 weeks is permissible. Some operators apply DPA by submerging or dipping the pallet boxes into a tank of the solution or by drenching the apples by flooding the solution over them before placing the pallet boxes in cold storage. The pallet boxes of apples should be well drained after treatment. The dipping tanks should have the solution agitated at all times and any scum that might have accumulated on the surface should be re- moved as it may contain DPA crystals. If these crystals are deposited on the fruit, they will injure or burn the fruit upon extended contact. DPA may be applied by spraying the fruit just before it is packed, but the fruit should be packed soon after harvest. Application of DPA in a spray just before waxing or the inclusion of DPA in the wax will not control scald. When the fruit is to be waxed, it should be treated at least 6 weeks before waxing or it should be wrapped in DPA impregnated wraps (22). Soft Scald Soft scald is frequently confused with stor- age scald, but it has a different appearance and is radically different in its cause and preven- tion. Soft scald seldom occurs on fruit picked at the proper stage of maturity and stored immediately at 30° to 32°F. It is usually caused when susceptible varieties of apples are delayed at warm temperatures after harvesting and are then placed in low-temperature stor- age (below 36°). It cannot be prevented by the use of chemical dips or oiled paper wraps, or by picking at an advanced stage of maturity. In its early stages soft scald may resemble storage scald, as faint patches of brown be- come apparent, but soft scald develops rather rapidly into slightly depressed areas of dis- colored skin. The margins of the affected areas are sharp, and the pattern is generally irreg- ular. The apple may have the appearance of having been rolled over a hot stove. Another distinguishing feature is the brown spongy tissue beneath affected areas. In certain varie- ties the disorder may be confined to the small points of contact where apples press against each other. When limited to this type of mani- festation, soft scald is sometimes referred to as “contact scald” and when found in mid- winter it rarely develops to greater propor- tions. Freezing injury may look like soft scald. Jonathan and Rome Beauty are the varieties most susceptible to soft scald. At the expense of a shortened storage life, susceptable lots of these varieties should be stored at 35° to 36° F. Controlled atmosphere storage will also pro- vide good control of soft scald (15). The same applies to Golden Delicious if not stored within 4 days after picking. McIntosh, Delicious, and other varieties are sometimes affected. In the Winesap, soft scald is largely confined to fruit that has been held in common storage for a period and then moved into cold-storage tem- peratures of 30° to 32°. Soft scald can be pre- 12 MARKETING RESEARCH REPORT NO. 924, U.S. DEPARTMENT OF AGRICULTURE vented by holding the fruit in 25-percent CO. gas for 24 hours before storage at 30° to 32°. Scaldlike Disorders Golden Delicious and Yellow Newtown apples that hang on the tree with the cheek freely ex- posed to the sun may have sunburn that is not very noticeable at the time of packing, but after a period in storage these areas take on an appearance that is difficult to distinguish from apple scald. This disorder should be diag- nosed as delayed sunburn. It does not ma- terially shorten the storage life of the fruit and when found on occasional specimens does not require the early disposal necessary when oc- casional specimens are found with storage scald. The only prevention is a more careful sorting of sunburned apples at the time of packing. Small sunken-scalded spots result from the contact of apples with Douglas-fir wood, such as with fir-tree props or bins constructed of this wood. Freezing Injury Injury from freezing ranges from no visible evidence following incipient ice formation in the flesh to a brown discoloration of the entire apple following “freezing to death” at pro- longed low temperatures. Intermediate stages of injury may appear as follows: a slight softening of the flesh; a flaky or corky charac- ter in a flesh lacking normal crispness; brown discoloration of tissue around the 10 fibro- vascular bundles and extending as threadlike fibers throughout the flesh; the appearance of sunken spots where the apples were bruised while frozen; and as soft scald. All of these manifestations should be interpreted as indi- cating a shortened storage life. After apples have been badly frozen, the skin becomes shriveled, the surface is discolored in irreg- ularly shaped areas, and the tissue beneath may be translucent and water-soaked or have some shade of brown. Badly frozen tissue be- comes dry and corky after prolonged storage. When slight freezing occurs near refrigera- tion coils or cold-air ducts, the frost can be removed by raising the temperature at those points to 82° F. But when the apples are frozen deep in the piles, a storage-room tem- perature of up to 40° and an active circulation of air between the packages will be necessary to thaw them out. The fruit should not be moved while frozen, as this will result in severe injury. The thawing of frozen apples at a tem- perature of 32° to 40° is recommended. A high temperature will accelerate ripening and cause greater dehydration of the fruit. To prevent shriveling, the relative humidity should be kept as high as possible during the thawing process, preferably above 80 percent. Jonathan Spot Jonathan spot is a skin disease giving the apple a freckled appearance from small black or brown spots that appear usually on the deep- colored areas. Although it sometimes develops on other varieties, especially Rome Beauty, from a commercial standpoint it is of im- portance only on the Jonathan. It may be con- fused with the brown-freckled appearance of Jonathans caused by spray or washing injuries, but these diseases are distinguished by their appearing earlier in storage, regardless of tem- peratures. Jonathan spot is prevented almost entirely by picking the apples before they are overmature and storing them promptly at 30° to 32° F. The disease, an indication of “old age,’”’ may develop on fruit still on the tree. Its appearance in storage is a warning that the fruit is being kept beyond its commercial stor- age period. Water Core Water core occurs in the fruit before it is removed from the tree. As it is usually as- sociated with advanced picking maturity, crops severely affected are ordinarily not considered well suited for prolonged storage. The water- soaked areas gradually become smaller during storage and, if they are not severe, may com- pletely disappear. Apples affected with water core never completely recover, however, be- cause the affected tissue has been weakened and is disposed to internal breakdown. In the Delicious, Rome Beauty, Stayman, and other softer varieties, internal breakdown may follow slight water core at the fibrovascular bundles. Apples that have apparently made a complete recovery while in cold storage frequently be- come worthless from internal breakdown through the fruit known as a Difference Meter, is capable of _ rapidly measuring optical density differences STORAGE FOR APPLES AND PEARS 13 | within 5 or 6 days after removal from cold storage. The disappearance of water core is hastened by holding them at temperatures that produce rapid ripening. As such ripening is not desir- able, however, the only recommendation that can be made is to limit the storage season as much as possible and keep the fruit under re- frigeration. In 1962 an instrument was developed which can detect water core by transmiting light (20). This instrument, of intact fruit. It is primarily a laboratory in- strument, and its use is a nondestructive method of determining the amount of water core in an apple. Pears Pears have a slightly lower freezing point | than apples and, not being subject to such low- _ temperature diseases as soft scald and brown core, can be stored at slightly lower tempera- tures, 29° to 31° being recommended. As pears are rather susceptible to shriveling, the relative humidity of the storage room should be kept above 85 percent, preferably - about 90 percent. Pears are more responsive to high tempera- ture than most varieties of apples, so that it is essential that heat be removed from them as _ rapidly as possible immediately after harvest- _ ing. They have a high rate of respiration, and the heat of respiration is an important con- sideration in storage, especially during the | cooling period. For successful storage, there- fore, the fruit at the center of packages must | be cooled approximately to the storage tem- _ perature within 48 hours before the packages are stacked in the permanent storage piles. _ This can be done by circulating 26° to 31° F. _ air through widely spaced stacks of packages _ immediately after they are packed. After this _ initial cooling, packages should be stacked so as to provide air channels for the continuous _ removal of the heat of respiration and for uni- _ form refrigeration throughout the piles. Stack- | ing away from the walls and on strips or floor racks is necessary to prevent the conduction of heat to the fruit. Pears may be held in cold storage and sub- sequently washed and packed without serious injury or disfigurement, provided ripening has progressed only slightly. The prevalence of scratches and other friction marks often found on fruit thus held depends on the stage of ripeness rather than being due to the influence of refrigeration. Holding the fruit for 2 or 3 weeks before washing and packing is safe if the fruit is kept at 30° to 31° F. from the time it is harvested. Loss of Ripening Capacity Following prolonged storage, certain varie- ties of pears may seem to be in excellent condi- tion but when taken to ripening temperatures they fail to respond. Although the color of the fruit may become yellow in the ripening tem- peratures, the flesh does not soften or become juicy. Bosc, Comice, Bartlett, and Flemish Beauty exhibit this characteristic and do so earlier in the season when stored at tempera- tures higher than 30° to 31° F. These varieties should be stored at optimum low temperatures and for periods not longer than the varietal storage season. Following storage, ripening must proceed promptly at optimum ripening temperatures. Optimum Ripening Temperatures Commercial varieties of pears grown in the United States do not ripen satisfactorily for eating while held at 29° to 31° F. Some varie- ties gradually become softer at these tempera- tures, while others may turn slightly more yellow but scarcely soften. All pears need to be withdrawn from cold storage and held at higher temperatures to ripen for eating. The optimum ripening temperature for most varieties is between 65° and 70° F. Bartlett has much better quality when ripened in this range than at higher temperatures. Bosc fails to ripen normally at lower temperatures. Kieffer has optimum quality when ripened at temperatures between 60° and 65°. Pear Rots Blue mold rot and gray mold rot are the most important storage rots in pears. Blue 14 MARKETING RESEARCH REPORT NO. 924, U.S. DEPARTMENT OF AGRICULTURE mold rot usually results from skin punctures. Gray mold rot may start at ruptures of the skin or at broken stems and spreads from fruit to fruit by contact. Once established, gray mold grows slowly in cold storage, but having the capacity to enter the unbroken skin of ad- jacent fruits, it often produces the so-called “nest rot” affecting a group of pears. The spreading from one pear to another can be prevented by packing pears in wrappers im- pregnated with copper. Sanitary measures in harvesting and packing, together with prompt cooling to temperatures of 29° to 31° F. are important factors in preventing losses from decay. Pear Scald In pear scald the skin of the fruit becomes dark brown and soft and sloughs off easily under pressure. The affected skin may become almost black and affords entrance for the decay fungi that usually follows. The disease does not appear until the fruit is aged in storage from being held too long or at too high a tempera- ture. Pear scald, other than the type on the Anjou variety, cannot be prevented by packing in oiled wrappers, but susceptibility may be lessened by picking before the fruit becomes too advanced in maturity and by storing at tem- peratures of 29° to 31° F. Anjou Scald The Anjou variety is subject to a mottled surface browning or blackening in storage. Unlike pear scald, this does not cause a skin disintegration that is deep-seated, nor does the skin slough off. When the pears are wrapped in oiled paper containing basic copper car- bonate (Hartman wrap), some benefit is ob- tained in the prevention of Anjou scald. Studies on this problem have been published (24). Cork Spot Cork, or cork spot, is characterized by small regions of dark-brown corky tissue appearing in the flesh of pears. When the affected tissue is near the surface, a small depression fre- quently appears and the skin at this spot may be slightly dark. Anjou is the variety frequently affected by cork spot. The disease is related to growing conditions in the orchard and is not caused by storage conditions. Affected fruit can be stored approximately as long as normal fruit, but its market value may be greatly de- preciated if cork spot is very prevalent. COLD-STORAGE PLANTS AND EQUIPMENT Refrigeration The best way to become familiar with re- frigeration is to work with it and use it. Each cold-storage plant has characteristics of its own. To take advantage of its good points and to avoid difficulties that may not be common to other plants, the operator must be familiar with his particular plant. General principles of refrigeration apply to all plants, however, and knowing these principles will enable an opera- tor to profit by his experience. These principles are covered in textbooks (16, 18, 19, and 35) ; more specific information is given in handbooks (1 and 33) on characteristics of refrigerants ; condenser, compressor, and evaporator; insula- tion values; fan and duct data; requirements of stored products; cooling surface; power re- quirements; and other matter. Pumping Heat The process of refrigeration might be likened to pumping air out of a tank until the pressure is lower than that of the atmosphere. Once the desired low pressure inside the tank is | reached, the only additional pumping necessary | is to remove any air that enters the tank by leakage, and then the pumping needed will de- pend entirely upon the leakage. In a refrig- erated space, it is desirable to maintain a | certain temperature below that of the sur- | roundings. Heat is pumped out until the desired | low temperature is reached, whereupon further © pumping is necessary only to remove the heat | that enters the chamber by leakage through walls and open doors or heat that is generated within the space. When pumping air from a vacuum tank, if only a slight approach to vacuum is required, STORAGE FOR APPLES AND PEARS 15 less power and a smaller pump are needed than for a high vacuum. The size of the pump re- quired and the horsepower of the motor de- pend upon two factors: (1) The quantity of air to be removed and (2) the pressure inside the tank. If too much air is allowed to enter the tank, the pump cannot remove it and the desired vacuum cannot be maintained. Sim- ilarly in a refrigerating system, if only a mod- erately low temperature is required, less power and a smaller compressor are needed than where a very low temperature is desired. Fur- thermore, if the refrigeration machinery does not have the capacity to pump out heat as fast as it enters the chamber, the desired low tem- perature cannot be reached. In extending the comparison, the factors de- termining the size of the pumps for the vacuum are (1) pressures, usually expressed in pounds per square inch (p.s.i.), and (2) quantity of air, expressed as pounds per minute. In the refrigerating system the factors are (1) tem- perature, expressed in degrees, and (2) heat, commonly expressed as British thermal units (B.t.u.). The term British thermal unit (the heat required to raise the temperature of 1 pound of pure water 1° F.) corresponds to the term pound (in pumping air), in that both ex- press definite quantities of the matter to be handled. Quantity of Heat Heat is not a substance and cannot be measured as to quantity by pounds or cubic feet but must be measured by the effect it produces. Heat is measured in intensity in units of temperature and in quantity by units of heat. In dealing with refrigeration problems, it is just as necessary to consider the quantity of heat to be handled as to speak of pounds of air or gallons of water when computing the neces- sary sizes of air or water pumps for given jobs. Just as 1 pound represents a very definite and measurable quantity of air, and it is still the same regardless of the pressure under which it is placed, so 1 B.t.u. represents a definite and measurable quantity of heat, and it too remains the same regardless of existing temperatures. The refrigeration demand upon the ma- chinery is frequently spoken of in tons. This usage had its origin in a comparison of refrig- erating capacity, or demand, with the refrig- eration obtained from melting 1 ton of ice. As 144 B.t.u. of heat are required to change 1 pound of ice to water at the melting point, 288,000 B.t.u. are required to melt 1 ton of ice. Where 288,000 B.t.u. of heat must be removed in 24 hours, 1 ton of refrigeration is required. If, for example, a temperature of 32° F. is to be maintained in a storage building, the refrigeration system will have to remove a quantity of heat just equal to that which enters the building. The heat entering may come from many sources. In the first place, if the outside temperature is above 32°, some heat will come in through the walls. This infiltration can be reduced by insulation, but not even the best insulation will exclude all heat leakage. If the building has cracks, or if the doors or windows are open and permit warm air to enter, an increased quantity of heat will be introduced, depending upon the outside temperature and the quantity of air. Materials having tempera- tures above 32° placed in the cooled space will introduce still another quantity of heat, de- pending upon the temperature, weight, and nature of the material. If the materials are living, as for example, apples, they will produce heat continually ; this heat is in addition to that which they contained when first put into stor- age. The heat from these and other incidental sources combines into the total quantity of heat the refrigerating system is expected to remove. If the system has sufficient capacity, the heat can all be pumped out. If the heat introduced into or produced within the building exceeds the capacity of the refrigeration system, some of it will remain in the fruit and cannot be taken out until the rate of heat intake drops below the rate at which it can be removed. Flow of Heat Heat always flows from the warmer to the colder object or substance. Heat will permeate everything, and no substance or material is known that will totally prevent or stop its flow. Some materials, known as insulating materials, 16 MARKETING RESEARCH REPORT NO. 924, U.S. DEPARTMENT OF AGRICULTURE will retard or resist the flow of heat. These materials such as cork, rock wool, styrofoam, and urethane are used as insulation in the walls and ceilings of cold-storage houses. Other material, like bright aluminum foil, prevent the passage or flow of heat by reflecting it away or back. Heat passes from substances or bodies of higher temperature to those of lower tempera- ture by (1) conduction, (2) convention, and (3) radiation, or (4) by a combination of these means. Conduction is the flow of heat through a solid substance or from one body to the other that are in contact. Heat flows readily through some materials like iron, copper, and aluminum. These materials are known as conductors. Convection is the transmission of heat by the flow of liquids or gases after contact with a heated source. The heat is conveyed from the warmer to the colder substance where heat transfer takes place. In cold-storage houses air currents are the most common agents convey- ing heat by convection. The circulating air is warmed by contact with the fruit and then the heat flows from the air to refrigerator cooling coils as it passes through the evaporator units. Radiation is the transmission of heat through intervening substances without heating the substance. The heat supplied to the outside of a building by the sun is by radiation, since the sun’s rays do not heat the air through which it passes but does heat the building walls or sub- stance where it is absorbed. Three Steps in the Refrigerating Process Heat, like air, is handled in definite quan- tities, but unlike air it cannot be moved bodily from one point to another. By its nature, heat moves from a place of high temperature to one of low temperature. A refrigerating system, or heat pump, takes advantage of this tendency. Heat from the storage room moves through the walls of the evaporator cooling coils to the ammonia or other refrigerant inside, which is at a lower temperature. The compressor then takes the vaporized gas with the heat it has picked up in the evaporator and by compressing the gas raises its temperature. The heat from the hot gas finally is transferred into the con- denser water because the water is at a lower temperature. Thus, the heat from the storage is now in the condenser cooling water, which may be either wasted or cooled by aeration for recirculation. These three steps in heat removal are accomplished by the three essential parts of the refrigerating system—the evaporator, the compressor, and the condenser (fig. 2) .4 * Bowen (6, pp. 2-3) describes the operation of the re- frigerator shown in figure 2 as follows: To utilize its latent heat of vaporization for refrigeration and to conserve the refrigerant, application is made of the physical law that the temperature at which a fluid boils or con- denses is raised or lowered, respectively, by increasing or reducing the pressure. To cause the refrigerant to boil at a low temperature in the evaporating coils and hence absorb heat on a low-temperature plane, the pressure in the coils is lowered by suction of the compres- sor.... To free the fluid of the heat absorbed in the refrigerator and return it to liquid form, the cold refrigerating gas coming from the evaporating coils is compressed until its tem- perature is raised above that of the water flowing through the condenser so that the contained heat can pass from the gas to the water. (In very small machines, air may be used instead of water.) The essential parts of a compression-refrig- erating system are an evaporator, a compres- sor, and a condenser. In the evaporator (the coils in the refrigerator) the liquid boils and in the process absorbs heat from the surrounding medium. The compressor is a specially de- signed pump that takes the gas from the evaporator coils and compresses it into the condenser coils, reducing its volume and in- creasing its temperature. The condenser con- sists of coils of pipe over or through which water or air flows to absorb the heat from the gas, which is thereby liquefied. In some systems the cooling water passes through an inner tube and the gas from the compressor through the annular space between the inner and the outer pipes. From the condenser the refrig- erant passes first to a liquid receiver, and then through a throttling or expansion valve into the evaporator coils, to repeat the process of transferring heat from the refrigerator to the water flowing through the condenser. The temperature of the liquid ammonia is reduced from the temperature of the receiver to that of the refrigerator by vaporizing a part of the liquid. STORAGE FOR APPLES AND PEARS ACK Ci Ra WSS PRESSURE REFRIGERATOR LU] N N N y SN AQ Y \SANASSSSS COMPRE / | } / / / / / \ REE LOW-PRESSURE SIDE FIGURE 2.—Essential parts of a co In the evaporator, or cooling coils, the quan- tity of heat picked up depends upon (1) the temperature difference between the refrigerant (ammonia or Freon) in the coils and the room air, (2) the area of coil surface exposed, and (3) the resistance to heat flow through the walls of the pipes or tubing. The resistance to passage of heat into the coil in turn depends not only upon the cleanness of the coil but also upon the velocity of air (or brine if a brine The expansion valve is of a special design and is capable of very fine adjustment. Its function is to so regulate the flow of the liquid refrigerant that suitable pressure and temperature conditions will be maintained. It is largely responsible for the control of tem- perature in the evaporating or cooling coils. Nc 6 Ray Ah il HEAD PRESSURE SSSA : S —— —j3§~ ———— r Sa ie DUCT USED FOR RETURN AIR — << ————— ot RSs = DUCT USED FOR DELIVERY AIR FIGURE 14.—Diagram of delivery and return ducts that may be used interchangeably with a reverse air system. Deflector vanes are used to equalize the quantity of air delivered from the varisized duct openings. As the distance from the fan room increases, these openings are made larger to equalize the flow of return- ing air. The number of openings is adjusted to the length of the duct. COLD-STORAGE MANAGEMENT AND PLANT OPERATION Many cold-storage plants are not utilized to best advantage, either because of shortsighted- ness in management or not operating at maxi- mum efficiency. During the cooling period many plants take in fruit faster than their equipment can cool it. As a result the fruit is not cooled to the holding temperatures until ripening is well advanced. Several managerial steps can be taken to improve conditions. Compressors and auxiliary apparatus need to be in good shape. Condensers must be clean and all available condenser surface used. Evaporating coils should be kept as free as possible from frost and the blowers used should circulate the maxi- mum volume of air. Good management includes such handling of the fruit as will utilize the plant to best advantage and such control over the operation of the plant and over the care of the equipment as will keep both at top operat- ing efficiency. Handling the Fruit Reducing the Initial Fruit Temperature The quantity of heat that must be removed from a package of fruit depends largely upon how warm it is when put into storage. If its average temperature can be reduced before storage, it will lessen the load imposed on the plant by each box. Fruit picked in the after- noon is ordinarily warmer than that picked in _the morning. Picked fruit left in boxes under | the tree is considerably cooler in the morning than at evening. In some districts fruit left under the trees overnight or picked in the morning may be at a temperature of 55° F. as _against 80° late in the afternoon. To cool 1 ton of fruit from 55° to 32° requires removal of 41,400 B.t.u. of field heat, as compared with | 86,400 B.t.u. for the warmer fruit. The cooling capacity of the cold storage would be more than doubled if the operator of the plant could | have the cooler fruit delivered. Leaving fruit out in the orchard to cool over- | night frequently results in its cooling faster than it would in a cold-storage plant that is being crowded beyond its capacity. It also re- sults in the fruit already in storage having a chance to cool faster and represents an excep- tional situation where a few hours’ delay in the 'orchard increases its storage life. These ad- 'vantages warrant curtailing afternoon de- liveries with such fruits as apples and pears and correspondingly increasing early morning deliveries, especially in plants with limited / cooling capacity, even at the expense of some | difficulty and inconvenience in handling and hauling. | Hydrocooling _ Hydrocooling, or cooling by the use of cold | water, has been used for many years for ‘rapidly cooling perishable vegetables and some | fruit, especially peaches grown in the Eastern _and Southern States (4). It has not been used , extensively for long-keeping fruits like apples | and pears. | Tests results reported by Blanpied (5) showed a discernible difference for the first 3 STORAGE FOR APPLES AND PEARS 39 months in lots of McIntosh apples that were hydrocooled or air cooled in 3 days and 1, 2, or 3 weeks. However, after 4 or 5 months in storage the hydrocooled, 3-day air cooled, and 7-day air cooled apples were about equal in quality. Recent research by Schomer and Patchen (28) produced similar results for Golden De- licious and Red Delicious apples. For these varieties when hydocooled or air cooled in 3 and 7 days, their storage life and quality were essentially the same. However, when air cooled in 14 and 28 days, their quality was inferior and storage life shortened. The same tests on Winesap apples did not indicate any quality change or length of stor- age life. The slow-cooling rate improved the quality for the test panel. Segregation of Long-Storage Fruit The Delicious variety causes the most serious storage problem in western apple districts be- cause of its storage-temperature requirements, its large tonnage, and its relatively short har- vest period. If the cooling capacity of the plant is sufficient to cool all these apples as fast as harvested, all the fruit should be cooled as quickly as possible. Since this is usually not possible, an attempt to cool all the fruit with equal promptness means that none of it is cooled quickly. In general, the longer a box of apples is to be held, the more important it is to cool it quickly. This is illustrated graphically in figure 15. Long-storage lots of fruit, then, should get more than an equal share of refrig- eration at harvesttime and short-storage lots less. Those lots for long storage should be put into rooms where the receipts would be limited to a quantity that could be cooled rapidly. Fruit for shipment during the harvest season or shortly thereafter would be deliberately with- held from any of the cold-storage rooms to save the refrigeration for long-storage lots. The procedure of segregating apples for long-, intermediate-, and short-storage periods places demands upon the management for more planning before harvest than a _ procedure whereby all the apples are treated alike. This planning should include selection of apples that are of optimum maturity and freest from in- 40 MARKETING RESEARCH REPORT NO. 924, U.S. DEPARTMENT OF AGRICULTURE HELD AT 40° 21 DAYS, THEN COOLED TO 32° IN 28 DAYS; HELD AT 32° TO FEB. 10 THEN COOLED TO 32° IN 4 WEEKS; HELD AT 32° TO. MAR. “ie HELD AT 32° TO APRIL 15 mee COOLED TO: 30°F. IN 6 WEEKS HELD AT 36° a DEC. 20 36°F. IN 7 DAYS 40°F. IN 7 DAYS 36°F. IN 7 DAYS 32°F. IN 7 DAYS 30°F. IN 7 DAYS SEPT... - OCT: L HELD AT 30° TO JUNE | ee NOV. DEC. JAN. FEE: MAR. — APR. MAY FIGURE 15.—Normal storage life expectancy of Delicious apples when cooled at different rates and stored at dif- ferent temperatures. For each week of exposure at 70° F. before storage, deduct 9 weeks of storage life at 32°; for each week’s delay at 58°, deduct 1 month of storage life at 32°. herent defects for preferential refrigeration over the long period on the one hand and the early marketing of weak, overmature fruit on the other. It may necessitate the use of cold- storage-in-transit privileges and shipping the fruit under the standard refrigeration service provided by the railroads for a part of the ton- nage scheduled for intermediate and early marketing, to conserve local refrigeration for promptly and adequately cooling the tonnage intended for marketing after December. Such a sacrifice in cooling early shipments is an ex- pedient and is desirable only when limited capacity prevents prompt cooling of the entire crop. Segregating to Avoid Soft Scald Development of soft scald in Jonathans and other varieties of apples, including Winesaps, is erratic and unpredictable. It usually can be traced to a quick reduction in fruit tempera- ture to 30° to 32° F. when the fruit is some- what advanced in maturity or is delayed at relatively high temperatures after picking be- fore going into storage. When such delays are unavoidable, the disorder may be prevented by | holding the fruit at 36°, or slightly above, for | the first few weeks of storage. When it is im- possible to get susceptible varieties into cold }j, storage promptly, they should not be cooled to | the 30° to 82° range generally recommended for apples but only to a moderate temperature (36°) and segregated for early sale. Therefore, avoid putting them in the same room with a | variety like Delicious, which should be held at 30° to 32°. Storage in separate rooms in which }_ the temperature can be controlled independ- | | ently is desirable. Although the fruit will not keep as long at this higher temperature, the | risk from soft scald will be avoided. Stacking Packages Lines are ordinarily painted on the floor of storage rooms (fig. 16) to indicate the spaces | for placing rows of boxes on pallets or pallet boxes and to facilitate even stacking. Maintain- | STORAGE eas PN-2384 FIGURE 16.—Lines painted on floor will facilitate plac- ing pallet loads or pallet boxes of fruit and help in providing uniform spaces for the movement of cold air through the stored fruit. ing an air space between rows at all points is important. A uniform spacing of 4 to 5 inches between rows is practically as effective in per- mitting cooling as wider spacing, provided headroom between the top of the boxes and the _ ceiling is sufficient. Careless stacking, however, in which some boxes in one row touch or ap- proach those in another, restricts air move- ment and retards cooling. A spacing of 4 or 5 ' inches is also needed to facilitate forklift truck | maneuverability between rows. This con- venience in trucking has regulated spacing in | most storage houses. To overcome slight irregu- larities in stacking, 4 inches may be considered a satisfactory spacing for the bottom pallets. The rows should be so laid out that the general direction of air movement is along the rows '| instead of across them. Stacking packages in contact with outside ‘| walls or floors should be avoided, as there is some heat transfer through conduction that affects the temperature of fruit in outside or | bottom packages. When pallet loads of fruit are | being stacked, spacing between the walls and ‘the pallets may be insured by using side rails, as illustrated in figure 17, or by fastening 2- by )6-inch planks to the floor around the outside of the room. On concrete floors an air space should be provided beneath fruit by stacking the fruit on pallets. FOR APPLES AND PEARS 41 To prevent the lower fiberboard boxes from crushing when pallet loads of packed fruit are stacked three or more high, 1- by 4-inch boards are placed on end at the four corners or be- tween the first and second boxes on each corner of the pallet (fig. 18). The boards are cut about 1 inch shorter than the height of the stacked boxes on the pallet. As the boxes are com- pressed a small amount by the pallet load above, the boards take up the load. The use of these boards eliminates crushing and improves the stability of the stack. In large rooms warm fruit may be brought in over a long period; this means that fruit that has been in the room for some time and has cooled is sometimes warmed by incoming fruit. This effect in unavoidable in some rooms, but by judicious stacking it can be kept at a minimum. Sometimes, the first fruit brought in can be stacked near the air-discharge ports so that after it is cooled it is not exposed to air coming from warm fruit brought in later. Overhead Space In most storage rooms air circulation is planned so as to have the primary movement over the tops of the boxes and through aisle PN-2385 FiGURE 17.—View showing side rails along wall to prevent stacking fruit too close to wall and prevent- ing air circulation. 42 PN-2386 FIGURE 18.—Pallet load of fiberboard boxes of fruit spaced with 1- by 4-inch boards placed on end and other pallet loads with 1- by 4-inch corner boards to take load of pallet above. spaces. The cooling in the interior of the stacks is accomplished partly by secondary, or convec- tion, currents up and down the spaces between pallet boxes. This cooling is effective only inso- far as the warm air that rises to the ceiling is moved away and replaced by colder air. Leav- ing reasonable space overhead permits suffi- cient circulation for carrying off the heated air. If the space is limited, the air tends to move along aisles or unfilled channels in preference to the ceiling space. When fruit is stacked too close to the ceiling, air movement is restricted and cooling is retarded and uneven. No rule has been established on the minimum space required over the boxes to permit good circula- tion, but leaving the truss space open for this is a good practice. If the primary air circulation can be forced to move over the top of the stacks and through the spaces between stacks, cooling will be more MARKETING RESEARCH REPORT NO. 924, U.S. DEPARTMENT OF AGRICULTURE rapid. Moving the cooling air to the outside walls and then down and back through the stack spaces will greatly assist in cooling the fruit. If natural convection is sacrificed by reduc- ing the ceiling space, forced circulation must take its place, otherwise the effectiveness of cooling will be reduced instead of increased. For this reason, if air is forced through the box spaces by cutting down circulation over the fruit, the boxes must be arranged carefully. Uniform spacing becomes even more important, and air channels that will permit diversion of air around the stacks of boxes must be avoided. Precooling rooms in which these conditions are met provide much faster cooling than rooms in which natural convection is depended upon for cooling the interior of the stacks. - Control of the Plant In a cold-storage plant the relatively large investment in machinery and construction can be justified only if it increases the value of the fruit stored. The value of a plant in maintain- ing this condition is largely determined by the way it is operated. Even the best designed plant with automatic equipment needs more or less continuous attention to insure the best results. Core Temperature To make the best use of a plant, it is essential to know what temperatures are being main- tained. One or two thermometers for showing aisle-air temperatures do not indicate the per- | formance of a plant. An operator needs to know core temperatures of the fruit, especially in parts of the room where cooling is difficult. Periodic observations of fruit temperatures will indicate what methods of stacking and air distribution will give best results and what I. parts of the room need special attention. Re- |, liable thermometers or thermocouples are necessary for this purpose. An investment in © equipment for obtaining accurate records of temperature in all parts of a storage is worth- while. Frequently, when actual fruit temperatures are measured, the results are disappointing. If they are, conditions sometimes may be mark- edly improved with little cost or inconvenience. STORAGE FOR APPLES AND PEARS 43 It is to an operator’s advantage to know just how quickly he can cool the fruit and how uni- formly he can hold the temperatures after it is cooled. In addition to the management’s responsi- bility to ascertain whether core temperatures are what they should be in all parts of the cold- storage plant, management has the further re- sponsibility of checking on fluctuations in temperature during the operating season. This is best done by the continuous operation of a recording thermometer, or thermograph, at a central point in each room. One type of such an instrument is shown in figure 19. A file of temperature records affords the management a protection against complaints of grossly irregu- | lar temperatures but does not insure optimum core temperatures at all positions throughout the stored fruit. Maintaining Humidity The relative humidity in storage rooms _ should be determined periodically to avoid at- _ mospheres that are relatively dry and likely to cause subsequent shriveling of the fruit. Sev- eral types of instruments are available for this purpose (fig. 20). If type A or C psychrometers are used, the relative humidity may be found in table 8. Maximum use of Equipment If during the cooling period some of the compressors must be shut off to avoid localized freezing at some points while fruit tempera- tures are too high at others, the capacity of the equipment is not being used to full advantage _ and some means for better distribution of the | refrigeration should be found. This usually _ may be done either by improving the air cir- - culation or increasing its volume. While ample circulation cannot compensate for inadequate | refrigeration, it does permit maximum use of _ the refrigeration available. Pending the time when the air-circulation system can be overhauled to give maximum use of the compressors, the management may take temporary steps to prevent freezing at local points during the cooling period. They usually involve removing the fruit or covering it where air is introduced and using portable fans to accelerate the movement of air away from the cold spots towards points where fruit tempera- tures are high. Operating Efficiency Keeping Equipment Balanced To get the best results from a plant, the various steps in the mechanical removal of heat must be balanced. That is, the heat picked up in the room must be transferred in succession from the fruit to the air, from the air to the cooling coils, from the coils to the compressor, and from the compressor to the condenser, where it is discharged to the cooling water. If in one or more of these steps, the quantity of heat that can be transferred is unduly re- stricted, the equipment performing the other steps cannot be worked to its greatest capacity. The condenser is doing its part if the head pressure is not excessive; and the cooling coils are not unduly limiting the capacity of the plant if the suction pressure is well up. Whether the air-circulation system is in bal- ance with the rest of the equipment, however, is not as easily known. During the cooling period, when the refrig- erating equipment is operating to full capacity, { ! { ; : ‘ a { i ; PN-2387 FicgurE 19.—Recording thermometers are useful for giving temperature fluctuations and providing a permanent file on cold-storage performance. 44, MARKETING RESEARCH REPORT NO. 924, U.S. DEPARTMENT OF AGRICULTURE ¢ oe ] ey =| 4 A = Sy ioe ae) PN-2388 FIGURE 20.—Psychrometers consisting of wet- and dry-bulb thermometers that can be used for determining the relative humidity of storage rooms: A, Sling type; B, wall type; and C, hand-aspirated type. the volume of air circulation may be considered in balance if the temperature difference be- tween delivery and return air does not exceed 10° F. A lower split is desirable, but if it is greater than 10°, increasing the volume of air circulation is beneficial. As the load is cooled and as less warm fruit is brought into the stor- age, the split will decrease and should reach 1° to 2°. After fruit temperatures become about stationary, a split exceeding 1.5° is an indication of insufficient air volume. During this period further cooling is not required, but temperatures must be maintained uniformily throughout the room. Uniformity of temperature depends first on an adequate volume of air. If the volume is sufficient, as indicated by the split between de- livery and return, and if temperatures in some part of the room are still too high, the air is not being distributed to the best advantage. Ammonia Pressures The gage pressures on the refrigeration equipment should be routinely observed. Too low suction pressures or too high head pres- sures are signs that the system needs attention. Ordinarily suction pressures below 20 to 25 pounds indicate that the cooling coils are not picking up heat as rapidly as they should. Head pressures of over 160 to 170 pounds indicate lack of sufficient cooling in the condenser. These limits depend upon the kind of system used, but the cause of any unexpected changes in pressure should be found and corrected. If pressures are normally outside these limits, the possibility of making adjustments or changes in the installation should be investigated to reduce power consumption and to get more re- frigeration. Table 9 shows how power consump- tion increases as the head pressures increase and the suction pressures decrease with am- STORAGE FOR APPLES AND PEARS 45 monia compressors. Suction pressures as high as 35 to 40 pounds and head pressures as low as 100 to 120 pounds can be obtained under favorable conditions. Pressure gages should be checked occasionally for accuracy, since they may get out of adjustment after long use. The temperature of liquid ammonia at vari- ous gage pressures is as follows: Gage pressure (pounds )* Temperature (° F.) Suction pressure: Below normal: | ae ete . _-.._._.. —28 De a ee, —17 Normal: I ppc coe le i a —8 5 5 pees ee aan nee yar enna a —1 20 ee ae ee 5 25 oe ee ee Se 2 ee 11 3 eee ee ee ee 17 pe eereee eee ot e 21 Head pressure: Below normal: A) ee ee ee a eee 26 0 a ee Pe tad Fe = 34 (Aone cok PC eS 50 Normal LQ 0) eer re eae ok oS, 63 3 P15 Soe a a eC 15 15 Seen eee. EE 84 1 AY soe a ce 93 200 ee eee ae 101 ‘Suction pressures seldom occur below 10 or above 35 pounds; head pressures seldom below 100 or above 200 pounds. Frosted Coils Accumulation of heavy layers of frost on cooling coils retards the passage of heat. Pipes or finned coils need to be defrosted frequently to get the most from a cooling system. Disposal of the ice and water from defrosting may be a problem in direct-expansion plants, but re- moval of the frost during the cooling period is essential. Brine Treatment In brine-spray plants the frost is washed off with brine, which is continually being diluted by the condensed water, making it necessary to drain off some of the solution at intervals and add more salt. The brine should not be any stronger than necessary to prevent accumula- tion of ice. One objection to brine-spray sys- tems is that upon exposure to air the brine tend to become acid. Unless this tendency is checked, the particles of brine carried by the air are very corrosive and may damage any metal with which they come in contact. The brine may be treated with a chemical to retard this corrosive effect. The instructions regard- ing such treatment, which are furnished by the company installing the equipment, should be followed carefully. If they become lost or for- gotten, new instructions should be requested. Care of Condenser The water used in the condensers leaves a deposit on the pipes that, if allowed to accumu- late, interferes with the transfer of heat. The water tubes of a condenser should be examined at least once each year, preferably before the harvest season, to make certain they are in good condition. If dirty, they should be given a thorough cleaning. Care of Compressor The compressor and other machines, includ- ing motors and pumps, need careful attention. Instructions furnished by the machinery manu- facturers should cover operation of the par- ticular machines in the plant and should be kept in the engine room and referred to fre- quently. Carelessness in operation or failure to observe the recommended routine may prove expensive in repairs. A well planned and cared for compressor room is shown in figure 21. Controls Automatic parts of the numerous types of control equipment used in various plants usually depend upon changes in temperature or pressure or are controlled by clocks. It will pay to become familiar with the principle of opera- tion of each item involved in automatic control. Ducts and Dampers The dampers and openings in ducts should be set open wide enough to permit the desired air distribution. In making adjustments the ports requiring more air should be opened to full capacity in preference to closing down dampers or openings at other points. When the temperature of the delivery air is too low, the ports should not be closed down to prevent 46 MARKETING RESEARCH REPORT NO. 924, U.S. DEPARTMENT OF AGRICULTURE TABLE 8.—Relative humidity of atmosphere by wet- and dry-bulb thermometers Relative humidity when depression (° F.) of wet-bulb thermometer’ is— | Air temperature SSS se = a a a eee aan (° F.) 0.5° 1.0° 1.5° 2.0° 2.5° 3.0° 3.5° 4.0° 4,5° 5.0° | Pct Pet Pet Pet Pet. Pet. Pet Pet. Pet Pet 7) ies a a ee a 92 85 11 70 62 55 48 40 33 26 BO ee ee et 94 87 81 74 68 62 55 49 43 37 Or ee et 94 88 83 17 72 66 60 55 50 44 Ogre shoes ae 94 89 83 718 73 67 62 56 51 46 1) Cs A ae ec oar 94 89 84 18 13 68 63 58 52 47 =} a ase 95 90 84 719 74 69 64 59 54 49 HF op ea a 95 90 85 80 15 70 65 60 56 51 a ee 95 90 86 81 76 71 66 62 57 52 BOg sete Sez ee eae 95 91 86 81 17 72 67 63 58 54 5 {ein AN eee ER 95 91 86 82 17 73 68 64 60 55 BQ pe ae a 96 92 87 83 79 15 71 68 64 60 A ri oe ee 96 93 89 86 82 78 74 rat 67 64 | Ae a er OR 96 93 90 87 83 80 fie 74 71 67 i 4 * Difference between dry- and wet-bulb readings. Water should not be freezing on the wet bulb while a reading is made. The humidities shown in this table apply only when the air is moving rapidly past the thermometers, as with the sling or aspirating psychrometer. TABLE 9.—Relation of head or condensing and suction pressures to horsepower requirements per ton for typical ammonia compressors 6-BY 6-INCH COMPRESSOR Suction pressure of— Condensing pressure (pounds) 10 pounds 20 pounds 25 pounds 30 pounds 35 pounds Hp. Hp. Hp. Hp. Hp. BOs ee 1.30 0.90 0.77 0.66 0.56 i) 5 a te ee eee 1.42 1.04 .90 -79 .68 1; See ne en 1.62 1.18 1.03 91 82 a 1: a enn PO OS A OE CE 1.75 1.33 1.17 1.03 93 2 25 ae ee a 1.94 1.47 1.31 217 1.05 DN 5 aaa ee a eS 2.12 1.60 1.44 1.30 ake by 205... 2.29 1.76 1.57 1.42 1.29 1) a eo ek er eae me 1.20 0.84 0.71 0.61 0.52 NOD se 1.32 20% 84 73 64 10 sa se 1.50 i Ibs Bf 97 86 77 1; ae 1.67 1.25 1.10 98 88 DOO Sa ee ee 1.83 1.39 1.23 1.11 1.00 ESOS 22 2.00 1.53 1.36 1.23 1.11 | freezing; instead the temperature of the air _ should be raised and as much volume as possi- ble permitted to circulate through the room. | Many plants have too little air circulation, re- \ sulting in high temperatures in parts of the room. Sometimes the delivery-air temperature ) is lowered in an attempt to correct this. If this temperature becomes too low for safety, closing | down the openings to prevent freezing aggra- | vates the condition instead of improving it. Freezing Near Coils In direct-expansion rooms the packages nearest the coils sometimes become too cold STORAGE FOR APPLES AND PEARS 47 PN-2389 FIGURE 21.—Arrangement of multiple compressors in engine room. even though other fruit in the room may be too warm. This localized low temperature is caused by the radiation of heat directly from the pack- ages to the coils, even though the air next to them may be above the freezing point. Here, the air circulation may be increased to keep the packages from getting too cold or, if necessary, a shield may be put between the boxes and the pipes. This shield is not to deflect the air but to prevent direct radiation; that is, to stop the “shining,” or radiation, of heat from the boxes to the cold surface of the pipes. This radiation takes place regardless of the temperature of the air between boxes and pipes. 48 (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) MARKETING RESEARCH REPORT NO. 924, U.S. DEPARTMENT OF AGRICULTURE LITERATURE CITED AMERICAN SOcIETY of HEATING, REFRIGERATION and AIR-CONDITIONING ENGINEERS. 1966. ASHRAE GUIDE AND DATA BOOK—APPLI- CATIONS FOR 1966 AND 1967. New York. 1024 pp., illus. BARTRAM, R. O., SCHOMER, H. A., PIERSON, C. F., and OLSEN, K. L. 1969. HIGH-QUALITY RED DELICIOUS APPLES FOR LATE-SEASON MARKETING. Wash. State Univ. Ext. Serv. EM 3033, 10 pp., illus. BATJER, L. P., SCHOMER, H. A., NEWCOMER, E. J., and Cover, D. L. 1967. COMMERCIAL PEAR’ GROWING. USS. Dept. Agr. Handb. No. 330, 47 pp., illus. BENNETT, A. H., SMITH, R. E., and Fortson, J. C. 1965. HYDROCOOLING PEACHES, A PRACTICAL GUIDE FOR DETERMINING COOLING RE- QUIREMENTS AND COOLING TIMES. U.S. Dept. Agr. Inform. Bul. No. 293, 12 pp., illus. BLANPIED, G. D. 1957. THE EFFECT OF COOLING RATE ON THE MARKET QUALITY OF MCINTOSH APPLES. Amer. Soc. Hort. Sci. Proc. 70: 58-66. BowENn, J. T. 1932. REFRIGERATION IN THE HANDLING, PROCESSING, AND STORING OF MILK AND MILK PRODUCTS. U.S. Dept. Agr. Misc. Pub. No. 138, 59 pp., illus. BROOKS, C., CooLEy, J. S., and FISHER, D. F. 1935. DISEASES OF APPLES IN STORAGE. U.S. Dept. Agr. Farmers’ Bul. No. 1160, 20 pp., illus. (Rev.) GERHARDT, FISK 1950. AIR PURFICATION IN APPLE AND PEAR STORAGE REFRIGERATION. Refrig. Engin. 58(2): 145-148. Feb. 1955. USE OF FILM BOX LINERS TO EXTEND STOR- AGE LIFE OF PEARS AND APPLES’ U.S. Dept. Agr. Cir. No. 965, 28 pp., illus. —________ and SAINsBuRY, F. G. 1951. PURIFYING AIR IN STORAGE ROOMS. Ice and Refrig. 120(6): 17-26. __ and SIEGELMAN, H. W. 1955. STORAGE OF PEARS AND APPLES IN THE PRESENCE OF RIPENED FRUIT. Agr. and Food Chem. 3(5): 428-433. May. HARDENBERG, R. E., and ANDERSON, R. E. 1963. A COMPARISON OF POLYETHYLENE LINERS AND COVERS FOR STORAGE OF GOLDEN DE- LICIOUS APPLES. Amer. Soc. Hort. Sci. Proc. 82: 77-82. (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) (24) (25) HERRICK, J. F., JR., MCBIRNEY, J. W., and CARL- SEN, E. W. 1958. HANDLING AND STORAGE OF APPLES IN PALLET BOXES. U.S. Dept. Agr., Agr. Mktg. Serv. AMS-—236, 41 pp., illus. SAINSBURY, G. F., CARLSEN, E. W., and HUNTER, C. L. 1964. APPLE PACKING AND STORAGE HOUSES— LAYOUT AND DESIGN. U.S. Dept. Agr., Mktg. Res. Rpt. No. 602, 43 pp., illus. Lutz, J. M., and HARDENBERG, R. E. 1968. THE COMMERCIAL STORAGE OF FRUITS, VEGETABLES, AND FLORIST AND NURSERY stocks. U.S. Dept. Agr., Agr. Handb. No. 66, 94 pp., illus. (Rev.) MACINTIRE, J. J. 1928. THE PRINCIPLE OF MECHANICAL REFRIG- ERATION. 317 pp., illus. New York. Macness, J. R., DIEHL, H. C., HALLER, M. H., and OTHERS. 1926. THE RIPENING, STORAGE, AND HANDLING OF APPLIES. U.S. Dept. Agr. Bul. No. 1406, 64 pp., illus. Motz, W. H. 1932. PRINCIPLES OF REFRIGERATION. 3d. ed. 1019 pp., illus. Chicago. NeEwcuM, K. M. 1946. MASTER SERVICE MANUALS—HOUSEHOLD REFRIGERATION MANUAL NO. 1. 144 pp., illus. Business News Publishing Co., 450 W. Fort St., Detroit 26, Mich. OLSEN, K. L., SCHOMER, H. A., and BIRTH, G. S. 1962. DETECTION AND EVALUATION OF WATER CORE IN APPLES BY LIGHT TRANSMIT- TANCE. Wash. State Hort. Proc. 58 :195-197. PATCHEN, G. O. 1961. AIR DOOR FOR COLD STORAGE HOUSES. (An Interim Report.) U.S. Dept. Agr., Agr. Mktg. Serv. AMS-236. 11 pp., illus. PIERSON, C. F. 1968. DIPHENYLAMINE FOR THE CONTROL OF STORAGE SCALD OF APPLES. 3 pp. U.S. Dept. Agr., Wash. State Ext. Serv., Wenatchee, Wash. ae, and ScCHOMER, H. A. 1961. CHEMICAL SCALD CONTROL. Produce Mktg. 4(5) :27-29. _. and ScHOMER, H. A. 1967. CHEMICAL AND NON-CHEMICAL CONTROL | OF ANJOU SCALD. Hort. Science 2(4): 151. RosgE, D. H.,McCotuocn, L. P., and FisHER, D. F. 1951. MARKET DISEASES OF FRUITS AND VEG- | ETABLES: APPLES, PEARS, QUINCES. | U.S. Dept. Agr., Misc. Pub. No. 168 |! (rev.), 72 pp., illus. STORAGE FOR APPLES AND PEARS 49 (26) SAINSBURY, G. F. (31) Smock, R. M. 1959. HEAT LEAKAGE THROUGH FLOORS, WALLS 1958. CONTROLLED-ATMOSPERE STORAGE OF AP- AND CEILINGS OF APPLE STORAGES. U.S. PLES. N.Y. State Col. Agr. (Cornell) Dept. Agr., Mktg. Res. Rpt. No. 315, Ext. Bul. 759. (rev.), 6 pp. 65 pp. (32) and BLANPIED, G. D. (27) ScHOMER, H. A. and McCo.tocu, L. P. 1969. THE STORAGE OF APPLES. N.Y. State 1948. OZONE IN RELATION TO STORAGE OF AP- Col. Agr. (Cornell) Ext. Bul. 440, 27 PLES. U.S. Dept. Agr. Cir. No. 765, pp., illus. 24 pp., illus. (33) TECHNICAL PUBLISHING Co. (28) _. and PATCHEN, G. O. 1943. REFRIGERATION. Ed. 2, rev., 295 pp., 1968. EFFECTS OF HYDROCOOLING ON THE DES- illus. Chicago. SERT QUALITY AND STORAGE OF APPLES (34) VAN Doren, A. IN THE PACIFIC NORTHWEST US. 1961. STORING APPLES IN CONTROLLED AT- Dept. Agr., Agr. Res. Serv. ARS 51-24, MOSPHERE. Wash. State Univ., Agr. 6 pp. June. Ext. Serv. EM 2129, 18 pp. Pullman, (20) __. GERHARDT, F., and SAINSBURY, G. F. Wash. 1954. POLYETHYLENE BOX LINERS FOR PEARS (35) VENEMANN, H. G. AND APPLES. Wash. State Hort. Assoc. 1942. REFRIGERATION THEORY AND _ APPLICA- Proc. 50: 193-198. TIONS. 264 pp., illus. Chicago. (30) and PIERSON, C. F. (36) WHITEMAN, T. M. 1967. THE USE OF WAX ON APPLES AND PEARS. 1957. FREEZING POINTS OF FRUITS, VEGETABLES, Wash. State Hort. Assoc. Proc. 63: AND FLORIST STOCKS. U.S. Dept. Agr., 198-200. Mktg. Res. Rpt. No. 196, 32 pp., illus. APPENDIX How To Make a Thermocouple The following suggestions on how to con- struct a thermocouple are not necessarily com- plete for all methods of making thermocouples. Each presents its own problems and experience will provide the best procedures to use. The procedures outlined here must be regarded as general enough to cover the requirements for constructing thermocouples to be used in indi- cating the temperatures in a cold-storage room for apples. Materials Two dissimilar metals such as two dissimilar metallic wires when joined together constitute a thermocouple. Some thermocouples are more sensitive than others. Since the instruments used in the Pacific Northwest are calibrated for copper-constantan thermocouples the following types of wire are used: No. 29 Copper wire, cotton covered No. 24 Constantan wire, enameled single- cotton covered enameled _ single- | ! The smaller the wire used the less cost per foot /and the greater the sensitivity of the thermo- couple. However, too small a wire will break easily and must be handled with care. Cutting Wire Cut both wires to length of the finished thermocouple. Remove the insulation and enamel for a distance of about one-half inch from one end of each wire by scraping with a knife to insure a good connection with the circuit. Twisting Wire With both wires extending the same distance, twist these two ends together. Fusing or Soldering the Thermocouple The twisted ends should be soldered with a resin core solder, then clip the end so that it is not over 14, to 3% in. long. Do not use acid core solder as it is conducive to corrosion and will shorten the life of the thermocouple. For better and longer lasting thermocouples the wires can be fused with a small electric are or gas torch. Electric arec.—The construction of an appa- ratus for fusing thermocouples junctions elec- trically is illustrated in figure 22. Assemble parts by nailing or screwing wood 50 base together, fasten porcelain sockets to base, and fasten metal carbon holder securely to support block. Porcelain sockets should be con- nected in parallel, connect one lead wire to 110 volt plug, another wire from sockets to metal carbon holder. Other lead wire is connected to alligator clamp. Tape or insulate all exposed metal connections. In using the electric arc, bare and scrape 14 inch of thermocouple wire, twist bare ends together, insert in alligator clamp with clamp gripping bare wire. Thermo- couple wire should protude 14 to 3% inch from clamp. Plug in extension cord to 110 volt outlet. By use of wooden handle press the wire into contact with carbon and slowly break contact, drawing an electric arc which fuses thermo- couple wire. A %e« fused ball should be formed on the end of the thermocouple wire. If arc is too hot for size of thermocouple wire, unscrew one resistor to cut the current down. CAUTION An electric are will burn the eyes so protect eyes with dark glasses or place a piece of smoked glass over the are area. Do not plug in unit until ready to fuse thermocouple and unplug unit before removing thermocouple wire. Remember when unit is plugged in there is 110 volts on all exposed places. Avoid touching a grounded circuit while using the apparatus to prevent being severely shocked. Gas torch.—When using a gas torch, use the following procedure: When welding, use an acetylene torch, and select a torch tip in proportion to the size of wire to be welded. (For the smallest gage wires use a No. 1 torch tip and for the largest gages use a No. 10 tip.) Fasten the torch in a vise so that the flame will be horizontal. Adjust the torch so as to get a neutral flame, about 4 in. long, with the white cone—surrounding the small blue cone—almost 3/4, in. long. Hold the twisted junction of the wires in the flame—at MARKETING RESEARCH REPORT NO. 924, U.S. DEPARTMENT OF AGRICULTURE 480 WATT RESISTOR (1-REQ'D) METAL CARBON HOLDER CARBON (5/16’ TO 3/8” DIA.) 360 WATT RESISTOR (1-REQ’D) THERMOCOUPLE WIRE ALLIGATOR CLAMP PORCELAIN SOCKET (2-REQ'D) WOOD HANDLE PIVOTED AT SCREW > WOOD BASE & FRAME APPARATUS FOR FUSING THERMOCOUPLE JUNCTIONS FIGURE 22.—Apparatus for fusing thermocouple junctions. the tip of the white cone—until both wires are a bright red, then dip in a fluxing mixture consisting of 6 parts of fluorspar to 1 of borax. (If fluorspar is not available, borax alone may be used.) Place the flux-covered twisted ends, immediately in the flame. Since one wire melts | at a lower temperature than the other, manipu- late the weld in the flame until both wires reach their melting points at about the same time. | This can be done by keeping the wire that melts first in the cooler part of the flame until the | other wire is about to melt. As soon as both wires reach the melting point, revolve the weld in the flame until both metals flow together forming a ball weld at the | tip. Use a moderately hot flame to avoid burning. After fluxing the metal, the weld should be> made, if possible, on the first attempt. Con- tinued heating at welding temperatures will | result in a poor weld. If a good weld is not made promptly, and a shorter thermocouple can be used, cut off the ends, make a new | twist, and repeat the procedure. Inexpensive Paint for Concrete Walls The following is an inexpensive and durable | paint for concrete walls: 50 pounds slack lime 15 pounds granulated salt 15 gallons of water a oe he Oe STORAGE FOR APPLES AND PEARS Mix the water with the ingredients to a thick slurry consistency for painting on concrete structures. Harvesting Maturity of Apples Because of the importance in harvesting ap- ples at the proper time for storage, the follow- ing research information on picking dates for apples in the Pacific Northwest is quoted in its entirety (2). Before 135 days from full bloom. Red Delicious apples are immature. They never develop high quality, are so disposed to scald that scald in- hibitors may not control the disorder, and— except for some Super Red Sports—they normally have inadequate color. Between 187 to 150 days from full bloom, Red Delicious can be stored for over six months and retain high quality providing they are free from water core. At 137 to 144 days, Red Delicious are gen- erally very susceptible to storage scald. T'hey should be treated with a scald in- hibitor as soon as possible after harvest. Delays should not be more than 10 days. By 145 days, most Red Sports have de- veloped their maximum color and have reached their peak of maturity for flavor, texture, and late storage potential. At this stage, Red Delicious have had significant water core in four years out of eight (1959 through 1966). In seasons when water core develops early, water-cored fruit should be segregated in the orchard and kept in separate lots at the ware- house for earlier marketing. At 145 to 150 days, Red Delicious have long storage potential in seasons when water core is not significant. They have superior flavor and are nearly as firm in the late storage period as apples harvested at 137 to 144 days. They are less suscepti- ble to storage scald than apples harvested earlier, but should still be treated with a seald inhibitor. After 150 days from full bloom, Red Delicious have excellent quality for the early marketing period, but do not have good potential for the late storage season. By 155 days from full bloom, Red Delicious | have had significant water core in six years | out of eight (1959 through 1966). In these years, from 40 to 70 per cent of the apples were affected and more than half of these ol had water core in the severe range. Even with excellent storage conditions, severely water- cored fruit begins to show internal browning in late January and early February. Fruit harvested in this late period loses firmness more rapidly than that harvested before 150 days. Pressure Testing The use of pressure testing to determine the maturity of apples at harvest time is not re- liable. A Magness-Taylor pressure tester can be used in the storage house to test the rate at which apple firmness is being lost during the storage season and is a method used to predict the future storage life of apples. Harvest Maturity for Pears In contrast to apples the flesh firmness of pears is the most satisfactory way of determin- ing their maturity. The picking maturity of pears varies slightly from district to district because of different growing conditions. Table 10 shows the recommended pressure for picking pears as determined by L. P. Batjer and others (3). TABLE 10.—Flesh-firmness recommendations for harvesting pear varieties ; Firmness* Variety : = Maximum Optimum Minimum Pounds Pounds Pounds Anjou a 15 13 10-11 Bartlett 19 17 15 Bose = : 16 13 11 Comice eee 13 it 9 Hardy ~~ a 10 9 Kieffer ~ 15 13-14 12 Seckel eee 18 16 14 Winter Nelis _. 15 12.5 11 *Magness-Taylor pressure tester with %g¢-inch- diameter plunger. vy U.S. GOVERNMENT PRINTING OFFICE O—424~107 ae ah bes ; aren Hs cys ih Se Sees Se tee MASUR BR HA mae RTE Mee eH REUSE URE (ie GANAS UNL ALCCRMCat aS ne UNIAN TAA NINE ASCE MEU GY ACH ais WN AER aielcaNi EN ra fate