TIGHT-FILL FRUIT PACKING tf. G. Mitchell • N. F. Sommer • J. P. Gentry Rene Guillou Gene Mayer CALIFORNIA AGRICULTURAL Experiment Station Extension Service CIRCULAR 548 THE TIGHT-FILL FRUIT PACKING METHOD consists of filling a con- tainer in a random manner with sized fruits, to meet grade standards; settling the fruit by vibration; and tightly fastening the lid to compress the top padding upon the fruit. When properly done, there is no opportunity for fruit movement in transit, thus reducing fruit injury. THIS CIRCULAR describes the tight-fill packing system and discusses all necessary procedures and requirements for those who want to use this new fruit packing system. It was developed over the past ten years to improve packing and handling of fruit, and to keep it competitive in the marketplace. It has been in commercial use for pears, plums, and apricots, and in limited commercial use for nectarines and peaches. Experimental results indicate that the method also may be useful for cherries and the less tender apple varieties. DECEMBER, 1968 THE AUTHORS: F. G. Mitchell is Extension Pomologist, Marketing, Agricultural Extension, Davis. N. F. Sommer is Lecturer and Pomologist in the Experiment Station, Davis. J. P. Gentry is Lecturer and Associate Agricultural Engineer in the Experiment Sta- tion, Davis. Rene Guillou is Associate Specialist in Agricultural Engineering (retired) in the Experiment Station, Davis. Gene Mayer is Laboratory Technician IV, Agricultural Extension, Davis. [2] TIGHT-FILL FRUIT PACKING light-fill fruit packing was developed as an integrated system of postharvest fruit handling that makes possible a high- volume output of high-quality fruit. It saves labor and materials, and also pro^ vides a pack well suited to modern mer- chandising methods, including repack- aging and bulk displays. In recent years, many cost-saving im- provements have been made in fruit pro- duction and harvesting operations. To keep fruit competitive, packing and han- dling methods must also be made more efficient, and the requirement of skilled workers must be reduced. Today's shortage of skilled labor and the short harvest season of most fruit crops make it difficult and costly to get or train a sufficient number of packers. However, skilled packers are essential for the "place-packing" methods that have been used widely. These methods gen- erally require hand placing of two or more layers of fruit in a specific pattern into a rigid lug or box, using some com- bination of wraps, cups, trays, baskets, shims, liners and pads to aid in position- ing and protecting the product. The re- sulting packages are to immobilize the fruit and at the same time to cushion the fruit against impacts. Fruit must be care- fully selected for size so that the com- pleted layer is laterally tight. Smaller fruits, such as cherries and apricots, often are packed by first facing with two layers of hand-placed fruits in an inverted con- tainer, and then filling the container from the bottom with loose fruit. Packages often are overfilled to allow the fruit to be compressed, so the packages bulge during lidding. The lateral tightness of the hand pack and this compression serve to immobilize the fruit during handling and transit. Older packing methods often caused injury A successful new packing method must consider all factors contributing to me- chanical injury of fruit. Types of injuries. Mechanical fruit in- juries consist of open wounds and bruises. Most open wounds (cuts, punctures, and abrasions) can be easily recognized as caused by defective handling or packag- ing: cuts by rough handling during pack- ing, dumping, or lidding; punctures by injury from a hard object, such as a fruit stem, during handling, packing, or transit; and abrasion by the fruit rubbing against a rough surface- — the picking con- tainer, the packing belt, or the shipping container. The cause of bruises (impact, compres- sion, and vibration) are harder to iden- tify. Impact bruises result from a sharp blow, such as a fruit falling against an- other fruit or against a hard surface. They occur during harvest or packing, or during handling of the packed containers. Compression bruises are caused by ex- cessive pressure on the fruit, usually from lidding or stacking of containers. Both impact and compression bruises appear as circular, cone-shaped flesh injuries which may or may not turn brown, and cannot always be noticed on the fruit surface (figure 1). Vibration bruising, often called "roller bruising" or "belt burn," results from re- peated and prolonged vibration of the fruit against an adjacent surface. Such injury can occur whenever the fruit is in motion; during transit to the packing facility, during movement through the packing system, or during subsequent dis- tribution. This bruise appears as an un- sightly browning on the fruit surface [3] ' ,.: -a* I £, i'% Fig. 1. Bruising injury of pears. Top row shows vibration bruising which damages the fruit surface but does not extend into the flesh. Lower row shows impact bruising which may not be visible on fruit surface, but extends well into flesh. which makes it more difficult to market (figures 1, 2). The injury also makes it easier for rot organisms to enter, and speeds moisture loss and physiological ac- tivity of the fruit, thus shortening storage1 or shelf life, or hoth. Older packing methods. Many fea- tures of older packing methods were de- veloped by trial and error in an attempt to reduce fruit bruising. Improved pad- ding of fruit packing equipment has helped to protect the product from im- pact bruising. Packing materials within the package have provided added pro- tection. Techniques of immobilizing the fruit have been useful in preventing vi- bration bruising during the transit. Past attempts to develop new packing methods often failed because no provi- sion was made for fruit protection. A loose-pack has been tried with many fruits as a substitute for existing place packs. This loose-pack was prepared by random filling of fruit into a container. A pad and lid were sometimes used. The fruit was not immobilized unless the con- tainer was overfilled and the fruit com- pressed during lidding. Such overfilling could result in serious compression bruis- ing. Any fruit which was loose within the container was likely to be seriously damaged by vibration bruising during transit. In such cases, damage in transit [4 differed widely, depending on differences in the transport vehicles, type of ride, and even the ability of the particular con- tainer or fruit to absorb vibrations. Thus, the loose-pack method greatly reduced the labor and packing material require- ments, but did not protect deciduous fruits during handling and transport. These mechanical injury problems were carefully considered in the develop- ment of the tight-fill pack. Vibration settling prevents loosening of the contents after packing, thus fruit remains im- mobilized during transit. The tight-fill packing method maintains a slight pres- ure on the fruits without container bulge. The result is a reduction of vibration and compression bruising problems. Fig. 2. Vibration injury in a commercial plum pack shipped to eastern market in loose pack. The bruising, although visible in this picture only in some fruit, appears in a browning of the fruit. DEVELOPMENT OF TIGHT-FILL PACKING Long-term studies have indicated the fol- lowing advantages of tight-fill packing: • Fruit can be delivered to market in better condition than hand-packed fruit. • Mechanization of fruit-packing pro- cedures is possible. • The resulting package is adaptable to handling procedures during distribu- tion, consumer packing, and display. Shippers contemplating conversion to this new packing method should consider its adaptability to specific fruits ; its effect on their packing facilities, labor require- ments, and packing and handling costs; and its effect on marketing. Tight-fill fruit packing is not complicated, but it should be thoroughly understood before being adopted — careful attention to every detail is essential to success. Requirements of a new fruit packing system Any new packing procedure must be viewed as an integral part of the overall fruit handling operation including trans- port, dumping, sorting, packing, cooling, and car loading. Your present equipment may not necessarily be satisfactory for a new system. Efficiency will improve only if your packing line is carefully designed and your equipment is selected or de- veloped to facilitate the necessary han- dling procedures. How much mechaniza- tion is required will depend on the scale of your operation. Give careful attention to the packinghouse layout regardless of how much of it is mechanized. Nature of tight-fill packing Tight-fill packing includes random .fill- ing of a container, normally with sized [5] and graded fruit; settling the fruit by carefully controlled vibration; padding the top of the fruit; and tightly fastening the container lid to compress the top pad- ding upon the fruit. When done prop- erly, no part of the procedure will damage the fruit. During vibration set- tling, the fruit is not compressed, but is rather moved into voids which were left during filling. In the resulting package, individual fruits are held firmly in place and cannot move during transit. The tight-fill packing method, if done properly, results in a highly uniform pack. In contrast, most hand-pack meth- ods vary with the skill of the individual packer. Studies of trial shipments showed that average injury of tight-filled plums was less than half when compared to standard packing methods. The reduc- tion of injury in peaches and nectarines was about one-fifth. Just as in a poorly prepared place pack, however, fruit in- jury can be severe if tight-fill is not done properly. Tight-fill packing is an improvement over the loose pack method because the latter makes no provision to immobilize the fruit, and affords no protection against transit injury. The tight-fill pack offers the same ad- H vantages as the loose-pack method: it makes more mechanization possible and thus reduces packinghouse labor require- ( ments. Machinery may be substituted for labor in many of the packing operations f4 if justified by the economics of labor and equipment costs and length of packing season. The degree of mechanization also «• depends on how much labor is available in the packinghouse during critical har- vest periods. < The receiver also benefits from the tight-fill pack. Because most fruit is sold * in either a consumer package or bulk display, it must be removed from the shipping container prior to sale. The ab- sence of wraps, cups, trays, baskets, shims, or dividers in the tight-fill pack greatly facilitates this rehandling. The tight-fill pack looks somewhat dif- ferent than the place-pack. Buyers may be - reluctant to accept the random pack ap- pearance of tight-fill for fear that it may indicate an inferior pack. A sustained promotion program is necessary to con- vince buyers that this pack will deliver fruit in better condition than other packs, and that the elimination of some packing frills can also reduce their handling costs. > REQUIREMENTS FOR TIGHT-FILL PACKING Tight-fill packing requires a specific se- quence of carefully performed steps. Each operation is essential to the satisfac- tory delivery of the product to market. No step can be left out or altered without en- dangering the success of the system. Careful adherence to all packing steps will result in a superior pack and en- hance both the immediate sale of the fruit and future acceptance of the packing system. Need for careful sorting Sorting systems used with other packing methods are not necessarily good enough for tight-fill packing. In hand-packing operations the initial fruit sorting is usu- ally followed up by a second sorting when the fruit is placed in the container. This second sorting is not possible with tight- fill packing. Thus initial sorting must be thorough. To facilitate sorting, every part of the fruit must be easily seen by the worker. Various rotating devices may be used to achieve this: rollers may slowly turn the fruit as it advances. Or, to minimize fruit scuffing, spaced, revolving rollers may pass over an advancing belt, turning the fruit very slowly. Both rollers and belt [6] Fig. 3. Fruit sorting table is divided into lanes. Each worker sorts only in a single assigned lane. Fruit is turned slowly as it advances. have independent speed adjustments (figure 3). A series of narrow belts, with workers stationed alternately on each side, may be preferable to a single wide belt in as- suring that no part of the fruit is hidden from view. Where space limitations dic- tate the use of a single wide belt, turning devices may be helpful in altering the position of the fruit. Adequate sorting space is very im- portant. The belt must have sufficient capacity to accommodate the most diffi- cult sorting job, because no further quality check is possible during the pack- ing process. Selecting the container The container must have sufficient stack- ing strength to protect the contents from compression, and must resist bulging after closing and during storage and transit. The requirements of the con- tainer will vary depending on whether it is to be used for immediate shipment or long-term storage. Both corrugated-paper and wood containers can be designed so they will provide the necessary strength. Two-piece corrugated paper con- tainers of full telescope design have proven satisfactory. Such containers are well-adapted to the filling and closing procedures used in tight-fill packing, and to inspection and display during han- dling and marketing. Corrugated paper containers must withstand high humidity during cooling and storage without serious deterioration. They need not be designed for multi- pallet stacking in storage, however. Pres- ent economics favor the use of some type of stacking frames or pallet support rather than an extra-strength container. Two methods are used to provide suf- ficient stacking strength of corrugated paper containers under high humidity conditions. One method consists of con- structing a container with excessive initial strength so that it will still protect the fruit after the container has lost part of its strength from high humidity. The other method consists of treating the container or the corrugated paperboard to resist moisture absorption. Moisture [7] Fig. 4. Corrugated container must be con- structed to resist bulging. Background con- tainer— HSC (half slotted container) construc- tion— permits bulging in the center part of lid and body. Container in foreground — AFM (all flaps meet) construction — provides more uni- form resistance to bulging in all parts of container. resistance in paper containers is pro- vided during manufacture by dipping in hot wax; by applying plastic-wax mate- rials to their surfaces; or by impregnat- ing components of the corrugated paper- board with wax or resin during manu- facture. If surface coatings are used alone, both surfaces of the corrugated paperboard must be coated. If only one surface is treated, the material can act as a barrier to trap moisture within the paperboard and hasten its collapse. Stacking strength is only one require- ment of the container. Successful tight- fill packing also depends on preventing container bulge. Thus both bodies and lids must be capable of maintaining pres- sure on the pack during storage and transit. This requires balanced construc- tion between body and lid and can best be provided by a container designed so that all flaps meet (AFM construction, figure 4) . Two-piece telescope contain- ers, AFM construction, in which both body and lid are made of 275-pound test corrugated paperboard, curtain coated on both surfaces, have performed well in commercial shipments. If wood is used, all shook, including lids, must be thick enough to resist bulg- ing and to maintain pressure on the fruit during transit. Thin slat lids or thin paper-laminated wood veneer lids and bottoms have not been adequate to pre- vent fruit movement during transit. A liner in wooden containers will prevent fruit scuffing. Chipboard liners and other single-thickness materials have given good protection. Untreated corrugated- paper liners in wooden containers have not proven satisfactory. Depth of container. To facilitate uni- form settling, use containers that are three to four times as deep as individual fruits are wide, regardless of your pack- aging material. Pears, peaches and nec- tarines require depths of approximately 9 to 12 inches for satisfactory results. Smaller fruits, such as apricots or small plums, may be successfully packaged in depths as shallow as 6 to 9 inches. Cher- ries will settle well in 4-inch containers; their containers should not be deeper than 5 to 6 inches, or compression injury may occur. Width of container. Horizontal di- mensions are important only in their effect on top or bottom bulge and on container handling. Square containers present problems in stacking, palletizing, and loading. Containers that are approxi- mately 50 percent longer than they are wide have been used successfully. Minor adjustments may be necessary to facili- tate equipment usage, fill weight, pallet stacking, or car loading. As new contain- ers are developed it would be highly de- sirable to establish standard horizontal outside dimensions for use with as many fruits as possible. The dimensions of standard contain- ers which may legally be used in Cali- fornia for shipping fresh fruits are listed in the California Agricultural Code. No other container dimensions may be used unless an experimental permit is ob- tained. The Code now includes containers which are currently in use for tight-fill packing of certain fruits. These dimen- sions may be changed through appropri- ate action as new industry needs arise. [8] Fig. 5. Fruit being sized on drop-roll sizer. As the rolls travel toward the foreground, the space between adjacent rolls expands to allow fruit separation. Mechanical sizing must be used to provide the high-volume output essential for tight-fill packing. Sizing In many hand-packing operations the worker has been required to eye-size the fruit at time of packing. Sometimes a mechanical sizer has been used for rough separations, with the worker doing more exact sizing during packing. The random filling techniques of the tight-fill require the use of mechanical sizers of sufficient accuracy to satisfy standardization re- quirements (figure 5). A recent unpublished study conducted by the California fruit industry estab- lished a basis to evaluate mechanical sizers for accuracy, capacity, and fruit injury. Tested were weight, slot, and diamond sizers. Weight sizers separate fruit according to differences in mass. Slot and diamond sizers measure fruit dimension — -slot sizers measure one di- mension, diamond sizers two dimensions. Fruit orientation on some dimension sizers is random, either static or vibrat- ing ; on others it is accomplished by fruit rotation. If selecting a sizer, consider ca- pacity requirements, sizing accuracy, ease of adjustment, fruit injury, and adaptability to your packing facility. An important factor in sizer selection is the coordination of the various pack- ing line components to allow uniform fruit flow. Thus the sizer should be adaptable to the characteristics of the fruit being handled, and must permit a smooth and effective routine adjustment and operation. Assembling corrugated paper containers The method for assembling corrugated paper containers will depend upon how much your packing operation is mecha- nized. If limited volume is packed, bodies and lids may be stapled or stitched in advance of filling. A conveyor or chute system may be used to move the bodies to the filling station and the lids to the weighing and inspection station. [9 V Fig. 6. Above: Table being used to assemble containers for auto- matic filling. After assembly, pads are placed in lids and containers are filled while inverted. Fig. 7. Left, top: After assembly, cartons are fed into chutes to supply automatic fillers. Because each filling station bundles a single size of fruit, size designations may be applied to the cartons at this point. Fig. 8. Left, bottom: Automatic fillers in use with pears. Empty carton tilts up to reduce initial dis- tance of fruit drop. Containers are filled while inverted. If the filling operation is hand assisted, the worker may set up the carton, fill the body, and then assemble the lid. In larger operations the containers may be case-sealed or closed with automatic top and bottom stapling after filling. Auto- matic fillers must be supplied from a container-feeding station at which the bodies and lids are folded and combined, and pads installed (figures 6, 7) . The fruit size designation can also be applied to each container as the container is fed to the filler. Filling When random filling the container (fig- ure 8), see to it that the fruit does not drop far. Pears have been shown to bruise in a 4-inch free drop onto a hard surface or an 8-inch free drop onto other pears. Mechanical fillers which prevent excessive drops into the container are available. Improvements are being made to combine minimum drops with high- capacity output. Tight-fill packing depends on filling to a constant volume. Volume is nor- mally approximated by weight, although fruit count could be used after precise sizing. For hand filling operations, have "over-under" scales located at each fill- ing station. Automatic fillers are equipped with scales or counters to control the changing of containers. If weight is used to estimate volume, it must be carefully determined for each variety. Once the fill weight is estab- lished, it can be standardized for all sizes of a particular variety. However, because shape and density vary, the proper fill weight may vary slightly with variety. For this reason a volume desig- nation offers some advantages over a weight designation for marketing tight- fill containers. Certain criteria can be used to deter- mine the proper fill weight. Fill the con- tainer sufficiently to prevent fruit move- ment after settling and closing, but not so full as to cause compression bruising during closing or subsequent handling. After vibration settling, padding, and closing are completed, the container should show no noticeable bulge. A se- vere shake of the completed container should impart only slight movement of fruit. As the recommended pads absorb moisture, they will swell and nest around the fruit. This initial determination of proper filling is especially critical for fruits which are highly susceptible to compres- sion bruising. When fruits such as peaches or nectarines are packed, check the height of fill after vibration settling in a few containers, by removing the lid and top pad and by passing a straight edge across the top of the container. In- dividual fruits should not protrude above the top edge of the container body. Also observe uniformity of fruit settling. Large voids in the pack indicate that Fig. 9. Check weighing of filled containers before vibration settling. Clear view of scale dial speeds this operation. [ii] either the settling procedure is improper, the container is under-filled or the fruit is too large for the depth of the container. Because both top and bottom pads are used for these tender fruits, greater total pad swelling will occur to compensate for looseness of the fruit after packing. Weight check When weight is used to measure filling, all containers must pass through a weight check station (figure 9) . Here the weight may be adjusted and the top fruit rough leveled. You must have enough weight stations to adequately handle the total capacity of the packinghouse. If these weight check stations are crowded, weighing will not be accurately done on all containers. The check scales should be easily read to within % pound. It is not sufficient to spot weigh a percentage of containers — every container must be weighed. Most hand-assisted filling operations are performed with the containers on an over-under scale. Because the workers are primarily concerned with output, this system by itself has not provided suffi- cient weighing accuracy. A check-weigh- ing station is still essential to insure proper filling of all containers. This weight check must precede vibra- tion settling. An improperly filled con- tainer will not settle properly, and fruit injury or damage in handling and transit may result. New developments of sizing and filling equipment may alter the need for this final weight adjustment. If a high per- centage of the containers can be filled to within the % pound tolerance, an auto- matic check-weighing station may be feasible. Such a system would divert only those packages requiring adjustment. Improved sizing accuracy would favor the use of count filling which would elim- inate all weighing. Weight-check stations will continue to be essential until filling accuracy is improved. [ Vibration settling Carefully controlled vibration is used to settle the fruit in the container. When properly done, vibration settling will not cause injury, even to ripe fruit. The set- tling sequence consists of a short period of free vibration, during which motion is imparted to all fruit within the container, followed by a short period of vibration with a light top pressure. This top pres- sure does not compress the fruit; rather it causes it to move into voids which were left during filling. The entire procedure requires only a few seconds, not long enough to impart measurable vibration injury to the fruit. Vibration accomplishes the settling which may otherwise occur during transit. Without this initial settling the fruit will be subject to subsequent loosen- ing within the package, possibly causing vibration bruising. Optimum fruit settling is provided by vibration of the filled containers at 800 to 1,100 cycles per minute with a vertical stroke of 3/16 to 5/16 inches imparting an acceleration of 3.0 to 3.5 g (accelera- tion of gravity) to the fruit. The con- tainer should vibrate without top pressure for 3 to 5 seconds, to assure that all fruit is in motion. As vibration continues, a light top pressure is applied to the fruit or the container lid for an additional 2 to 4 seconds. Top pressure is maintained until vibration ceases in order to move fruits into voids. If the vibration period is too short, the fruit will not properly settle; if too long, vibration bruising may develop — the same injury which occurs during transit. The total time for this operation should be as short as possible consistent with good settling; usually 5 to 8 seconds. Vibration settling can be accomplished with a very simple device. A small table or box, mounted on soft springs, and fitted with motor-driven eccentric weights will satisfy the basic requirements. Al- though the circular motion imparted by 12] such a unit is satisfactory, the vertical component is most effective in settling. Straight vertical motion can be supplied to such units through the use of counter- rotating eccentric weights. The vibration table and the eccentric drive must be carefully balanced on such a unit. The natural frequency of the spring-mounted table should be well below the operating frequency. The natural frequency of the table will be under 300 cycles per min- ute if the springs are soft enough to be compressed % mch by the weight of the table. Commercial tight-fill packing equip- ment is available which incorporates these basic components. One simple unit consists of a vibrating table beneath a vertical top pressure unit (figure 10). The number of containers which can be handled per hour is limited by the oper- ator who must position each container and initiate the vibration sequence. An- other unit, designed on a reciprocating principle, pulls one or more containers at a time across the vibration table and Fig. 10. Left: Vibration settling of pears. Operator applies top pressure during vibration, and staples lid to body at end of sequence. Fig. 11. Below, top: Apricots being fed to reciprocal vibration settling unit. Note fruit level above container. Fig. 12. Below, center: Apricots passing through reciprocal vibrator. Top pressure is applied near end of vibration sequence. Fig. 13. Below, bottom: Tight-fill packed apricots after completion of vibration settling sequence. Note uniform, flat pack of fruit. applies top pressure in sequence (figures 11, 12, 13). The number of containers that can be handled per hour is limited by length and speed of the reciprocating top pressure unit. Units are also available which pass a continuous flow of packages across the vibration table, applying pres- sure with a top-mounted roller conveyor (figure 14) . The continuous flow of these units makes them capable of high-ca- pacity output. Any of these units are capable of satisfactorily settling the fruit if properly adjusted. The vibration requirements must be carefully followed to achieve good set- tling. Improper frequency and stroke may give you the desired acceleration but not good settling. For example, vi- brators used in packing sawdust grape chests, operating at 1,800 cycles per min- ute and 1/16-inch stroke, will give an acceleration of about 3 g, but are inef- fective in settling fruit. You can estimate the stroke of a vi- brator by firmly holding a sharp pencil in a stationary position against the unit so as to scribe the pattern of motion. With the vibrator stopped, height of the pencil line will give a close approxima- tion of the stroke. You can estimate the frequency by calculating pulley ratios and motor speed, or you can carefully Fig. 14. Vibration settling of pears on a con- tinuous flow vibrator. Roller conveyor applies top pressure as vibration proceeds. vwymmm BartlettPear measure it with a tachometer or strobe light. When you know stroke and fre- quency, you can find the acceleration of the unit by using the chart in figure 15. For more precise determinations, vibra- tion meters are available which will measure both displacement and accelera- tion. Although such units are relatively expensive, they can be useful in deter- mining the proper adjustment of a vibrator. Padding A pad must be placed over the fruit be- fore closing the lid (figure 16). The slight compression applied during lidding nests the pad around the top fruit (figure 17). This initial compression is subse- quently supplemented by pad swelling (caused by absorption of moisture) to maintain a slight pressure on the pack. This pad swelling counteracts the ten- dency for looseness that develops as a result of minor moisture loss and fruit shrinkage (figure 13). Envelope pads filled approximately % inch thick with either redwood bark or excelsior have performed well in tests. Both have shown the ability to swell under high-humidity conditions. The ex- celsior wood fibers are manufactured in CYCLES 1200 1100 1000 PER MINUTE 900 800 ACC ELERA' HON (g *s) 7 /, 7~ / 3.0 A / /// / / '// \ // / /// 1.0 '///, \ \ 3'l6 \ 5'l6 \ 7'.6 ''2 STROKE (inches) Fig. 15. To find acceleration, follow vertical line of your stroke value until it hits diagonal line of your frequency, then follow horizontal line to the left to determine acceleration of your unit. [14] Fig. 17. Above, top: Cutaway view of pad in position over top fruit in container. Slight pres- sure of lidding holds pad firmly against fruit. Fig. 18. Above, bottom: Pad after transit showing effect of swelling which caused pad to nest around top fruit in container. Fig. 16. Top pad is placed over fruit before lidding the container. such a way that moisture causes them to uncurl and swell the pad. Redwood bark pads manufactured at 200 pounds per 1,000 square feet of pad and excelsior pads manufactured at 1.12 pounds per 1,000 square inches of pad (160 pounds per 1,000 square feet of pad ) have given satisfactory results. Recommended min- imum weights of pads of these materials may be obtained from figure 19. A bottom pad has also been used with very tender fruits, such as peaches and nectarines, to protect against impact bruising during handling of the con- tainer. This bottom pad may be identical to that used on top of the pack. Impact bruising of these fruits can become a problem when this bottom pad is omitted. Closing The completed container should be closed with sufficient pressure to firmly seat the lid against the body (figure 20) . A lid not fully seated may move about in tran- sit, or other containers stacked on it may press it down and crush the fruit. If the lid is not firmly fastened, the contents may quickly loosen, causing transit bruis- ing to the fruit. A closing press will be needed to apply this pressure to corrugated paper con- tainers. Some machines combine this with the top pressure unit used in settling the fruit (figure 10). The corrugated- paper container cover may be fastened to the body by stapling. A properly ad- justed retractable anvil stapler permits tight closure without fruit damage (fig- ure 21) . The top pressure plate and side staplers may be combined into a single automatic unit. Closing pressures of ap- proximately 2 pounds per square inch are satisfactory to firmly seat the lid. With proper filling and settling this top pres- sure will not cause fruit compression in- jury. [15] tfehfcS »/>^j £*ce /riot Hi (.0 »*f6+r/$ P*d L**i xH ft ' / yS 2« — . si- 33. ±& vr- /x^^ ^ It ■ It- /Z 3o- / /// /^yj^ ^K ' ^^\ ^^ ;a if- Ifc^pn i , , _j. i \ 1 Fig. 19. To find minimum net weight per bundle of 100 pads of either excelsior or redwood bark, follow vertical line of the pad width until it intersects diagonal line of the pad length, then follow horizontal line to the left and read weight from appropriate column. Pads of these mate- rials which equal or exceed these minimum bundle weights and are relatively uniform in thickness should perform well in tight-fill packing. [tuato- > wdiftai :f$&^&i&f ^^st^S^^^^ :A^^imif ■£j^WMti&28&A ^P Fig. 20. Cutaway view of corrugated con- tainer showing the lid tightly seated against the rim of the body. Tight seating is necessary to maintain the tight-fill pack and thereby avoid fruit injury resulting from movement during subsequent handling. Fig. 21. Cutaway view showing use of staple to fasten lid to body of telescope corrugated paper container. If properly adjusted the re- tractable anvils of the stapler tightly clinch the staple without penetration through the inside wall of the container. [16] Fig. 22. Case-sealing pear cartons. Flaps are glued, folded and compressed until glue sets. Wooden boxes may be closed with a standard lidder which applies pressure through a top platen. Platens which are contoured to fit a bulge pack are not satisfactory, and should be redesigned Fig. 23. Automatic tight-fill packer. Single unit applies vibration settling seals flaps, and fastens lid to body. for a flat pack. Snap-on covers which have been designed for some wood and corrugated containers have not main- tained sufficient pressure to prevent fruit movement. [17] Some installations utilize corrugated paper containers which have been com- pletely assembled and fastened before fill- ing; others will require sealing after fill- ing. If carton flaps are sealed after filling, the sealing should also come after the vibration settling. Attempts to seal filled containers before vibration settling will result in poor container closure, fruit in- jury, and subsequent poor settling. Both a case sealer (figure 22) and automatic top and bottom staplers, are satisfactory. One high-capacity commercial unit combines all settling, sealing, and closing operations into a single machine (figure 23) . As the container enters this machine, the flaps are folded and the fruit is settled by vibration. Following this, the flaps are opened, glued, refolded, and the glue al- lowed to set in a compression section. During compression, side staplers fasten the lid to the body of the container. MANAGING THE PACKED CONTAINER Palletizing If room cooling is to occur after packing, space the containers on the pallet to allow cold air circulation past all surfaces (fig- ure 24) . Stability of the load must be pro- vided with such spacing. Whenever pos- sible, stabilize containers by cross stack- ing on the pallet. If this does not provide sufficient stability, you may use several alternate methods including solid stack- ing of top and bottom layers with spaced intermediate layers; wood or corrugated paper lath placed under the top layer of containers ; or straps or twine tied around the upper part of the load. Vertical pallet spacers have occasionally been used to provide a completely rigid load. Spacers must be located so as not to interfere with air circulation around the containers. If unitized pallets are to be shipped, pallet strapping will be necessary to prevent container shift during transit. Cooling The fruit must be thoroughly cooled to recommended holding temperatures be- fore loading for transit. The thoroughness of cooling should be checked by measur- ing the core or pit temperatures of fruit in the center of containers and pallets. Normal air cooling rates depend on con- tainer venting and spacing. Vent patterns and requirements will vary with the type of fruit and container dimensions. Cor- rugated paper containers have cooled sat- isfactorily with venting of approximately 5 per cent of the side area. A pattern which has proven effective consists of four vertical slots on each side, with two slots placed low and two slots placed high to aid air convection (see figure 24) . This venting pattern also adapts the tight-fill packed containers for rapid heat removal through the use of forced-air cooling. Less or no venting is required if the fruit is thoroughly cold when packed, or if the fruit is suited to slower cooling and can be held for a longer, thorough cooling be- fore loading. Because considerable automation is possible in tight-fill packing, it may be Fig. 24. Tight-fill plum containers stacked on pallets for cooling. Note cross stacking and spacing of containers. [18 feasible to cool the fruit before it enters the shipping container. The only hand operations required in a highly auto- mated plant are fruit sorting and grad- ing, weight adjustment, and pallet stack- ing. The fruit can be refrigerated through most of the packing procedure, but such a system requires efficient cooling before packing, and temperature checks as part of the packing operation. The feasibility of such a system depends on the need and economics of cooling cull fruit, the length of the delay between harvest and sorting, and the temperature requirements of the fruit. Regardless of loading method, fruits should be thoroughly cooled before tran- sit. Mechanical refrigeration, which has been replacing ice in transport equip- ment, is designed to facilitate transport of the product, not to serve as a portable cooler. Mechanical refrigeration in rail cars and trucks has ample capacity to maintain existing fruit temperature but not to rapidly cool the product. Thus, the fruit must be thoroughly cooled before loading. Storage Storage, regardless of packing method, requires a constant low temperature and high relative humidity with air velocity just high enough to prevent the develop- ment of "hot spots" in the system. Con- sult a refrigeration handbook for storage recommendations for specific commod- ities. The storage of corrugated paper con- tainers will pose additional problems. Such containers, even though designed to withstand high relative humidity, should receive special care in multi-pallet stack- ing. Use pallet frames or supports to pro- tect the lower pallets. Permanent pallet frames in the storage room will provide complete support (figure 25). This will slightly reduce storage room capacity, but will greatly protect the container and make the fruit more accessible. l& ' . : Fig. 25. Tight-fill packed pears in storage in permanent pallet racks. In this system, each pallet is independent of all others. Various wood or metal pallet supports or "crutches" may also be used. These supports are fitted to the pallet as it is loaded. One such support consists of a piece of angle iron cut slightly less than the height of the palletized cartons, with a small flat plate welded to the top. These are placed at each corner of the pallet and secured by tying a light rope around the center of the loaded pallet. Such pal- lets must be carefully loaded and posi- tioned to assure security in a storage room (figure 26). Fig. 26. Pallet supports of "crutches" being used for tight-fill pear storage. The corner sup- ports carry the weight of top pallets. [19] Fig. 27. Tight-fill packed plums loaded solid in a rail car. This method is suitable only for thoroughly cooled fruits with a fairly low respiration rate. Loading Corrugated paper containers nest well, and do not require stripping or blocking to immobilize them if loaded tightly into rail cars. No bracing is needed except to take up any slack in the center of the load. The load should be squeezed before plac- ing the final tiers of containers. Solid loads of thoroughly cooled pears and plums in corrugated paper containers have carried in good condition with standard car refrigeration (figure 27). The ability of thoroughly cooled fruits to carry successfully without air circula- tion depends upon their respiration rate and time in transit. Pears and plums have carried well, but the projected warming of cherries by heat released from respiratory activity during transit indicates that this fruit must have some air circulation. Projected warming rates are usually high because they are based on the assumption that no heat is re- moved from a solid load, while in prac- tice some heat removal does occur. Non- theless, the projections suggest that solid loading for cherries would be extremely dangerous. Peaches, nectarines and apri- cots are intermediate in respiration rate and should also have air circulation. Loads should be spaced for air circula- tion whenever danger exists that all fruit has not been thoroughly cooled, or where excessive warming might occur during transit. If corrugated paper containers Fig. 28. Carloading by use of the solid- spaced pattern. Alter- nate tiers of contain- ers are spaced, and immobilized through application of angle corrugated strips. Note hand-operated air stapler used to quickly fasten strips. 20 are spaced in the load, the ends rathe; than the sides should face the channel. This arrangement will minimize bulging which can weaken the container, may al- low the fruit to loosen, and thus expose it to transit bruising. For tight-fill corrugated paper con- tainers a loading pattern has been de- signed which combines good temperature management with container protection and load stability. This solid-spaced pat- tern, illustrated in figure 28, alternates solid tiers with spaced tiers. Spaced tiers are immobilized by treated corrugated paper angles fastened to the containers. Every fruit in the load is within a reason- able distance of an air channel. The load- ing pattern can easily be learned, and is economical in both labor and dunnage use. Watch the details of immobilizing the spaced tiers of this solid-spaced load. The angle corrugated paper strips are curtain coated to prevent weakening throughout transit. You may fasten them with re- tractable anvil staplers, but the stapler must be adjusted for solid clinching into the container. You need not staple strips to each layer of containers, but the top three layers should be stripped, and at least alternate layers below this. Standard channel loading methods — those used in truck vans — may be used for corrugated paper containers. These channels allow sufficient air circulation to prevent the development of "hot spots." The solid-spaced load found effective in rail cars can also be used in vans if ade- quate air channels exist in the floor. The amount of air circulation through any spaced load depends on the fan capacity of the vehicle. Corrugated paper containers loaded into ice refrigerator cars must be pro- tected from moisture which collects on the ice bunker walls and adjacent floor. Containers in contact with this free mois- ture can be seriously weakened or col- lapsed, allowing loosening and shifting of the entire load. A corrugated paper sheet tacked to the bunker wall to the height of the load, and extending approximately 2 feet onto the car floor will provide this protection. Wooden tight-fill containers require the same special loading methods used for other types of wooden containers. Spac- ing may be provided for temperature management using some type of strip or block loading method and bracing. Regardless of the fruit, packing method, package or loading pattern used, you should have a complete record of the temperature of the fruit at loading. Make temperature checking a regular part of your loading operation. Open sample con- tainers going into the load and take pulp or core temperatures of the center fruit in the box. Take repeat temperatures with each change in lot. Use these records to anticipate and prevent problems, and to relate loading condition with out-turn re- ports. SPECIAL CONSIDERATIONS Pears Large volumes of tight-fill packed pears have been shipped commercially during recent years. Many carloads have gone to eastern receivers. This fruit is well- adapted to tight-fill packing. Because it is highly susceptible to transit bruising, loosening of the fruit, either in wrap-pack or tight-fill, must be avoided. Normal cooling of pears does not require the use of side vents in the container. Pears have carried well in solid loads provided the fruit was thoroughly cold at the time of loading. [21] Plums and apricots Fairly large volumes of tight-fill packed plums and apricots are being shipped commercially with good results. Both fruits appear to be well-adapted to tight- fill packing. Successful shipments of tree-ripe apricots have been reported. Try tight-fill packing of soft, ripe fruits first on a limited basis, using the packing and shipping suggested for peaches. Many solid loads of cold plums have been shipped successfully. However, over- loaded facilities or the desire to ship the fruit immediately sometimes results in incomplete cooling, so that spacing for air circulation in transit may be desirable. Peaches and nectarines Tight-fill packing of these fruits has shown promise in laboratory tests and trial shipments. Limited commercial ship- ments have been highly successful when the solid-spaced loading pattern was used to facilitate temperature management during transit. Because these fruits are often shipped at an advanced stage of maturity, and thus are very susceptible to impact and compression bruising, watch out for the following in tight-fill packing: • Avoid overfilling. • Use a pad on the bottom as well as on top of the container. • Use a container of sufficient strength to support all weight during stacking and transit. • Use container of sufficient depth to assure uniform settling. Tight-fill packing does not appear to be adapted to those few early varieties which develop a soft tip while the shoulders re- main hard. Because peaches and nectarines are in- termediate in respiration rates, always load them to allow air circulation. The solid-spaced load facilitates good tem- perature management during transit. Cherries Laboratory tests and limited trial ship- ments indicate that tight-fill packing would improve the delivered quality of sweet cherries. The present "loose pack" could be modified to a tight-fill pack with only minor procedural changes. Use top and bottom pads with this fruit. Fill depths of 4 to 6 inches are accept- able with cherries. Deeper containers are undesirable, causing increased impact in- jury with compression and loosening of the fruit, and subsequently allowing in- creased transit injury. Cherries are tender, subject to rapid deterioration, and have a high respiration rate, producing considerable heat which must be removed during transit. Cool cherries quickly and thoroughly before loading and space containers for air cir- culation during transit. The solid-spaced loading pattern offers possibilities for this fruit. Apples Limited tight-fill packing tests have been conducted with apples, with variable re- sults. Tender varieties, such as Golden Delicious showed excessive impact bruis- ing. A firmer variety, Yellow Newtown, was shipped sucessfully using the proce- dures recommended for peaches. The se- verity of the transit bruising problem with apples has not been thoroughly ex- plored and requires further evaluations. Other fruits Limited evaluations and observations have also been made with oranges, avo- cados, and mature-green tomatoes. Tight- fill packing appears to have sufficient po- tential for all of these fruits to warrant further evaluations. Experience has ranged from preliminary laboratory tests with mature-green tomatoes, to laboratory tests and trial shipments with avocados, to observations of oranges under actual [22] packing and shipping conditions. No rec- packing. The method appears to have im- ommendations can he made for use of this portant advantages to all handlers, hut packing method for any of these fruits receivers were reluctant to try any varia- without further extensive study, includ- tion from the place pack. Acceptance has ing laboratory tests, careful trial ship- been improving, however, as buyers have ments, and limited commercial explora- gained experience with consistent good tion. arrivals of tight-fill packed fruit, and have become familiar with the ease of re- Market acceptance handling the product for bulk display or As the volume of tight-fill packed fruit consumer packaging. Because of the ad- has increased, problems of market accept- vantages of this system to all fruit han- ance have declined. Early resistance de- dlers, an industry-wide effort to speed its layed the widespread adoption of tight-fill acceptance may be advantageous. If you wish to read more about tight-fill fruit packing and other methods, the following publications are suggested : Ferris, R. T. and R. K. Bogardus. Storing fruits and vegetables on pallets in whole- sale warehouses. USDA, M.R.R. 622, 1964. Gentry, J. P., F. G. Mitchell, and N. F. Sommer. Engineering and quality aspects of deciduous fruits packed by volume-filling and hand placing methods. Trans. Amer. Soc. Agr. Eng. 8(4) :584-39, 1965. Guillou, R. Coolers for fruits and vegetables. U.C. Agr. Exp. Sta. Bull. 773, 1960. Guillou, R. Settling packed fruit by vibration. Trans. Amer. Soc. Agr. Eng. 6(3) : 190-94, 1963. Guillou, R., N. F. Sommer, and F. G. Mitchell. Simulated transit testing for produce containers. Tappi 45(1) :176A-79A, 1962. Mitchell, F. G. 1957 transit tests of vibrator packed pears. U.C. Proc. Fourth Trans- portation of Perishables Conf . pp 82-84, 1958. Mitchell, F. G., J. P. Gentry, R. Guillou, and M. H. Gerdts. Tight-fill peach packing reduces costs and transit bruising: laboratory and transit tests. Calif. Agriculture 19(11): 12-14, 1964. Mitchell, F. G., J. P. Gentry, N. F. Sommer, and R. Guillou. Tight-fill packing of deciduous fruits, U. C. Agr. Ext. Ser. Pub. AXT-173, 1965. Mitchell, F. G., J. P. Gentry, N. F. Sommer, and R. Guillou. Progress made in tight- fill packing. Blue Anchor 48(2) :25-26, 1965. Mitchell, F. G., W. C. Micke, F. P. Guerrero, and G. Mayer. Packing sweet cherries to reduce transit injury. Calif. Agriculture 21(8) :6-7, August 1967. Mitchell, F. G. and N. F. Sommer. Developments in fruit packaging. U. C. Proc. 1967 Perish. Hand. Conf. pp 25-28, 1967. Mitchell, F. G., N. F. Sommer, J. P. Gentry, G. Mayer, M. H. Gerdts, and J. H. LaRue. Tight-fill pack nudges forward. Western Fruit Grower 19(1), 1965. O'Brien, M. and R. Guillou. An in-transit vibration simulator for fruit handling studies. Amer. Soc. Agr. Eng. paper No. 68-119, 1968. Reed, R. H. and R. H. Dawson. Economic-engineering cost studies prove value of tight-fill peach packing. Calif. Agriculture 18(11) : 14-15, 1964. Reed, R. H., F. G. Mitchell, J. P. Gentry, R. Guillou, M. H. Gerdts, B. C. Bilbo, and R. H. Dawson. Technical and economic evaluation of new and conventional meth- ods of packing fresh peaches and nectarines. U. C. Information Series in Agric. Econ. No. 64-1, 1964. [23] Sommer, N. F. Surface discoloration of pears. Calif. Agriculture 11(1) :3, 1957. Sommer, N. F. Pear transit simulated in tests. Calif. Agriculture 11(9) :3, 1957. Sommer, N. F. Transit injury to fresh fruits. U. C. Proc. Fourth Transportation of Perishables Conf. pp. 76-81, 1958. Sommer, N. F. and D. A. Luvisi. Choosing the right package for fresh fruit. Package Engineering 5(12) :37-43, 1960. Sommer, N. F., F. G. Mitchell, R. Guillou, and D. A. Luvisi. Fresh fruit temperatures and transit injury. Proc. Amer. Soc. Hort. Sci. 76:156-62, 1960. Stollsteimer, J. F. and L. L. Sammet. Packing fresh pears. Calif. Agriculture 15(10) : 2-5.1961. To simplify this information, it is sometimes necessary to use trade names of products or equip- ment. No endorsement of named products is intended nor is criticism implied of similar products not mentoned. \-lm I2,*68(J4869)J.F.