Reserve ash A Sar CORE List QUALITY SORTING OF RED DELICIOUS APPLES BY LIGHT TRANSMISSION Marketing Research Report No. 936 Agricultural Research Service UNITED STATES DEPARTMENT OF AGRICULTURE Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. ACKNOWLEDGMENTS The writers acknowledge the assistance of Karl H. Norris for instrumentation advice, David R. Massie for help with data analyses, and staff members of the Market Quality Research Divi- sion for cooperative service as taste panelists. Contents Page Summary: = 2 222 5 a ee eee i 2a. sea ee Ree al Introduction, 22222). ee ee ee eee 1 Materials and methods, 2222.2. 22a, ee ee ee eee 2 1965. exploratory ‘work 2222422222 920 eee Ee eee << 2 1966" test qe =e ee eV ae Le SSS als AY NR eran eS 2 TOG eteS ta ee ee HWE ks ooh 2 wn ate eS 8 eS 5 Resultsiand discussion = 222 == 22-2 es ee ee ee 5 1965 ‘exploratory work) == 35s mes ee ee ee ee ee ee ee 5 LOG Gites t= ae en Ee ee ee ee ee ein Ba ee ee 6 LOG Tatest: 2 2 = ae Sees ee wes Sot: ae a So Se eS Ae ee ee ee 13 Conclusions: and recommendations: .2 222. = 2 ee Mune See 38 20 Ibiterature:..citéd j= _ 22> S259 ss ee A ee ee ee 21 nF Trade names are used in this publication solely for the purpose of providing 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. Washington, D.C. Issued May 1972 For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402—Price 20 cents Stock Number 0100-1521 QUALITY SORTING OF RED DELICIOUS APPLES BY LIGHT TRANSMISSION BY BARBARA B. AULENBACH, JOHN N. YEATMAN, and JOHN T. WORTHINGTON Market Quality Research Division, Agricultural Research Service SUMMARY In a 3-year test, AOD(700-740 nm.) (the optical density difference between 700 nm. and 740 nm.) was a more reliable indicator of qual- ity in Red Delicious apples than AOD (580-640 nm.). Apples with low AOD(700-740 nm.) values (low-chlorophyll content) compared with those in the high range were generally sweeter, less tart, more flavorful, and higher in overall quality. The relationship between AOD (700-740 nm.) value and firmness varied from year to year. For Red Delicious apples harvested either over an extended (30-day) period or a more nearly typical commercial (9-day) period AOD (700-740 nm.) value at harvest was related to eating quality after as long as 6 months’ stor- age at 82° F. The proportion of apples in each AOD (700—- 740 nm.) category shifted during a 30-day harvest period. More apples in the low-chloro- phyll (high-quality) category were found in the later harvests. INTRODUCTION Light transmission is an established nonde- structive technique for evaluating the internal quality of many horticultural products. Al- though an apple transmits less than 0.1 percent of the light falling on it, the characteristics of this transmitted light have been related to quality and maturity (2). Norris (5) described an instrument for meas- uring spectral transmittance curves of intact agricultural products. He illustrated the possi- ble use of these curves to indicate maturity, internal color, and internal defects. Less mature Jonathan apples were distinguished from more mature Jonathans by higher absorption in the chlorophyll region (675 nm.) and lower absorp- tion in the region around 550 nm. The difference meter, developed by Birth and Norris (2), measures the optical density (OD) *Italice numbers in parentheses refer to Literature Cited, p. 21. of a sample at two wavelengths chosen from complete spectral curves and computes the dif- ference, AOD (\l-A2). A measuring wavelength related to the desired characteristic and a refer- ence wavelength must be carefully selected to successfully evaluate internal quality. Sidwell and others (7) found that AOD (700- 740 nm.) correlated +0.957 with log chlorophyll content of Elberta peaches. They concluded that light transmission appeared promising for peaches as an indicator of chlorophyll content and stage of maturation. Yeatman and Norris (8) sorted apples for eating quality with an automatic internal qual- ity (IQ) sorter They reported a correlation coefficient of —0.957 between log chlorophyll content of apples and AOD(740-695 nm.), Taste panelists preferred apples in the low- chlorophyll category, even after 6 months’ storage at 32° F. Eastern-grown Stayman, Winesap, and Golden Delicious were the varie- ties sorted successfully. Testing the same IQ sorter in the Pacific Northwest, Olsen and others (6) sorted Golden Delicious apples by internal chlorophyll, as measured by AOD(690—-740 nm.). The taste panelists gave apples in the low-chlorophy]ll category the highest ratings for dessert quality. Apples in the high-chlorophylll category repre- sented three harvests and varied in acid con- tent. The authors (6) concluded that categories of Golden Delicious apples obtained with the IQ sorter are more closely associated with quality than with maturity. The objectives of this research were to (1) search for wavelength pairs that might be more closely related to apple quality than AOD (695-740 nm.), (2) evaluate light trans- mission as a quality-sorting technique for Red Delicious apples, and (3) compare controlled atmosphere (CA) and conventionally stored apples that had been previously sorted by light transmission. MATERIALS AND METHODS 1965 Exploratory Work Spectral curves of intact Red Delicious apples were obtained at 10 nm. intervals from 380 to 740 nm. with a multipurpose spectrophotometer in the Beltsville Instrumentation Research Laboratory, Beltsville, Md. Red Delicious apples from two harvests, about 1 week apart, were included for each of the following strains: Standard Red and an unidentified red bud sport from Howard County, Md., and Starking from Washington State. Eighty apples per harvest of each strain were measured. The optical density at 650 nm. and the fol- lowing optical density differences (AOD) were taken from the punched-tape record of the spectral curve for each apple: 580-630, 580- 640, 590-640, 600-640, 630-660, 630-720, 680- 730, 680-740, and 700-740 nm. These apples were then stored in conventional storage at 32° F. for 4 months. At the end of this stor- age period, six experienced taste panelists rated general eating quality and sweetness on peeled wedges from each apple. These panelists used a 10-point rating scale (2— very poor, 9 —- very good; 2—very sour, 9—very sweet). Red lights in the taste panel booths masked differ- ences in apple flesh color. Average taste panel scores for each apple were correlated with each of the values taken from its spectral curve to select a light-transmission measurement that was most closely related to apple quality. 1966 Test Red Delicious (Red King) apples were har- vested weekly for 4 weeks (September 15- October 19) from an orchard near Mercersburg, Pa. On each harvest date, 10 bushels were picked from three trees selected at random from a block of mature trees. After mechanical sizing, apples 3 to 314 inches in diameter were selected for light-transmission sorting. A 4-filter model of the difference meter (2) was used for all light-transmission measure- ments. In this abridged spectrophcotometer, four interference filters are arranged in a wheel, and any two optical density differences can be read simultaneously on two meters. On each meter, the 100-unit scale can be divided into sections of any desired width, representing categories. Categories based on a range values are more practical than exact numerical values (fig. 1). Fifty apples, selected at random from each harvest, were checked for water core, using AOD (760-815 nm.) (3). Water core can in- crease experimental error by causing apples to be incorrectly sorted. Water-cored apples ap- pear to the difference meter to be more mature than they really are at harvest because the translucent tissue transmits more light. Internal browning in stored water-cored apples causes them to appear to the difference meter to be less mature. Since no water core was found in the sample, a presorting of all apples was not necessary. In the sorting room the temperature was maintained at 45° F. because large temperature fluctuations can cause variable difference meter readings. One fluorescent tube provided light in the sorting area. It was filtered with green cello- phane to minimize visible light that would cause chlorophyll in apples to fluoresce. If this gee Il x PPS GAPE R ALCL KAAY RRS AA cy Y WS FOUR-FILTER PHOTOMETER FIGURE. 1.—Schematic of 4-filter difference meter. precaution were not taken, fluorescing apples would cause errors in light transmission instru- ment readings. Difference meter settings for quality sorting were 0.5 OD full scale span for AOD (580-640 nm.) and 1.0 OD full scale span for AOD (700- 740 nm.). A preliminary sort showed that the range of test apples could be sorted into five categories by AOD (580-640 nm.) and into four categories by AOD(700-740 nm.). Each cate- gory represented 20 units on a 100-unit scale. Twenty bushels of apples were sorted by each wavelength pair, keeping the four harvests separate. The weights of apples sorted into each category were recorded according to harvest, and percentage distributions by weight were calculated for each category. The relationship between harvest date and category may be use- ful in predicting the best time to harvest for high-quality apples. One hundred apples per category were needed for the following experimental plan: 10-apple composite samples tested for 5 consecutive days, at harvest and after commercial CA storage (3 percent oxygen (O,), 2-8 percent carbon dioxide (CO,), 32° F.). To obtain 100 apples per cate- gory, apples from all four harvests had to be combined in the composite samples. The per- centage distributions calculated during sorting were used to make up 10-apple samples repre- sentative of all apples sorted. By using this method instead of choosing apples randomly from the four harvests, the five composite sam- ples for any category were as similar as pos- sible. The procedure is illustrated by the follow- ing example for AOD (580-640 nm.) : Percentage Number of (by weight) apples Harvest in category 1 in sample 1 _ 24 2 2 59 6 3 —_ 12 1 4 Pe ee ee 5 i Total, category 1 100 10 Laboratory and taste panel tests were con- ducted in October 1966 and April 1967. To elimi- nate any time-of-day effect, categories of one wavelength pair were evaluated in the morning and those of the other pair in the afternoon, alternating these assignments over the 5 days. Optical density differences were measured after storage to note any changes. Laboratory Tests and Taste Panel Procedures Firmness was measured with a Magness- Taylor pressure tester (38- to 30-lb. scale), using a %,-inch diameter probe with a penetration of 4, inch. Two pared areas on opposite sides of each apple were tested. Apples were then peeled, cored, cut into wedges, and cubed with a french-fry cutter. Cubes from the 10 apples in a sample were thoroughly mixed to form a composite. Soluble solids were read on an Abbe refractometer, using juice squeezed from 150 grams of apple cubes in a Carver press. Fifty milliliters of juice was titrated with 0.1N NaOH to pH 7.0, and acidity was calculated as malic acid. Apple tissue (150 grams per sample) was freeze dried before chlorophyll extraction with 85-percent acetone. The chlorophyll was trans- ferred from the acetone phase to anhydrous ethyl ether by repeated extraction in a separa- tory funnel. Spectral curves of the ether extract were obtained with a Bausch and Lomb 505 recording spectrophotometer, and chlorophyll content was calculated as micrograms per gram of dry weight. The extraction and calculation procedure was adapted from a modified Asso- ciation of Official Agricultural Chemists method (8). Five experienced judges scored portions of each composite sample for texture, juiciness, sweetness, tartness, apple flavor, and overall reaction, using the rating scale in figure 2. At OVERALL TEXTURE JUICINESS SWEETNESS SCORE TARTNESS FLAVOR REACTION TOUGH VERY JUICY VERY SWEET 7-# 7 VERY TART LIKE VERY MUCH ue nea, eke pe LIKE 676 MODERATELY SLIGHTLY MODERATELY MODERATELY FULL CRISP JUICY SWEET J eee rtavorep LIKE SLIGHTLY se os at ikea 444 pean bakes NEITHER LIKE NOR DISLIKE SLIGHTLY SLIGHTLY SLIGHTLY SLIGHTLY WEAKLY MEALY DRY SWEET 3-3 Tarr FAVORED Meare eC lan aye eis me Be iS SC SOD ISTIKE MODERATELY VERY DISLIKE VERY DRY NEUTRAL 1-41 NEUTRAL FLAT MEALY VERY MUCH FIGURE 2.—Apple quality rating scales, 1966 and 1967. each sitting, judges tasted four or five samples, randomly presented one at a time, in separate booths under red masking light. 1967 Test In the 1967 tests, the comparison of two wavelength pairs, AOD(580-640 nm.) with AOD (700-740 nm.), as measurements of apple quality was continued. Standard Red Delicious apples, harvested over a 9-day period, were purchased from a packinghouse in Charles Town, W. Va. The apples (31-inch diameter) were a mixture of West Virginia Extra Fancy, U.S. Fancy, and U.S. No. 1 grades. The experimental plan included two types of 32° F. storage at Beltsville (CA and conven- tional), four test dates (at harvest and at 2, 4, and 6 months’ storage), and two replications (days) per date, using composite samples of 10 apples. About 2,000 apples were sorted by each of the two wavelength pairs. A preliminary sort with the difference meter showed that the 0.5 OD full scale span used for AOD (580-640 nm.) in 1966 needed no adjust- ment. For AOD(700-740 nm.), the full scale span was changed from 1.0 to 0.5 OD to obtain more than one category. Because 1966 results indicated that three categories would sort as effectively as four or five, apples were sorted into three categories by each wavelength pair. Each category represented 25 to 30 units on a 100-unit scale. Conditions in the sorting room were the same as in 1966. For the actual tests, 200 apples were selected at random from the apples in each category, 5 100 for each storage. Difference meter readings for both wavelength pairs were recorded for each apple to study the relationship between AOD (580-640 nm.) and AOD(700-740 nm.). Laboratory and taste panel tests were con- ducted in October and December 1967 and in February and April 1968. At the start of each 2-day test, 20 apples were chosen at random from each category in the two storage rooms. Difference meter readings for the two optical density differences were recorded for compari- son with readings at harvest. Laboratory pro- cedures were the same as those used in 1966, except that chlorophyll was extracted only from apples sorted by AOD(580-640 nm.). Taste panel procedures were also the same, except that judges tasted six samples per sitting. The atmosphere in the CA room was modified by an Arcogen unit with an Arcat oxygen burner. Because this room could not be tightly sealed, the average oxygen level was 6 percent, higher than the 1 to 3 percent found to be best for Red Delicious CA storage (1). The carbon dioxide level in the CA room averaged 2 per- cent, and the relative humidity in both storage rooms was 85 to 90 percent. The Arcogen unit was shut down for about 8 hours when the 2- and 4-month samples were removed. Although the atmosphere in the CA room was modified, it varied considerably from recommended condi- tions. This CA room was part of an experi- mental system undergoing its first tests. Unless otherwise noted, all differences dis- cussed in Results and Discussion tor 1966 and 1967 are statistically significant at the 5-percent level. RESULTS AND DISCUSSION 1965 Exploratory Work Taste panel scores for general eating quality correlated poorly with all light transmission measurements (average r — + 0.150). Corre- lation coefficients for sweetness judgments versus optical density differences were con- sistently higher than those for general eating quality. In scoring sweetness, panelists could concentrate on one quality factor and varia- bility among panelists was lower. Correlations of sweetness versus optical density differences were highest for the second harvest of the Standard Red apples, the strain that also covered the widest quality range. For these apples, AOD (580-640 nm.) was the wave- length pair most closely related to sweetness scores (yr = + 0.741). This correlation coeffi- cient could be increased to + 0.948 by selecting only those apples scored extremely different in sweetness (averaging 3 or 6 on a 10-point scale). Using this selective method with AOD 6 (630-660 nm.), the correlation coefficient was +0.760 and with AOD (700-740 nm.), —0.791. Based on its relationship to sweetness, AOD (580-640 nm.) was selected for tests with AOD (700-740 nm.) comparing the effectiveness of the two pairs of wavelengths in sorting apples for quality. 1966 Test Relationship Between Harvest Date and Light Transmission Category For both AOD (580-640 nm.) and AOD (700- 740 nm.), the proportion of the total apples in a harvest sorted into each category changed from week to week during the 30-day harvest period. Harvests 1 and 2 yielded many apples with low AOD (580-640 nm.) values and high AOD (700-740 nm.) values (high chlorophyll). In contrast, a large proportion of the apples from harvests 3 and 4 had high AOD (580-640 nm.) values and low AOD (700-740 nm.) values (low chlorophyll) (figs. 8 and 4). If either measurement (AOD) is closely re- lated to eating quality, the relationship between optical density difference value and harvest date could be used to decide when to harvest for the greatest yield of high-quality apples. Difference Meter Values (AOD’s) After Storage at 32° F. for 6 Months Immediately after sorting at harvest by either AOD (580-640 nm.) or AOD (700-740 nm.), apples were equally distributed among the categories before being placed into storage (figs. 5 and 6). After 6 months’ storage, AOD (580-640 nm.) values for some apples decreased while others increased, resulting in a wider spread of values (fig. 5). Relationships between AOD values measured after storage and eating quality and between physiological changes dur- ing storage and changes in AOD’s were not determined. For AOD(700-740 nm.) values, a striking shift from positive to negative values occurred during storage (fig. 6). Although a slight de- crease in AOD (700-740 nm.) values might be expected as chlorophyll content decreases dur- ing storage, this shift from positive to negative cannot be explained. Laboratory and Taste Panel Tests AOD (580-640 nm.).—Apples sorted by AOD (580-640 nm.) were not different in firmness at harvest, as shown by Magness-Taylor results and panel texture scores (all categories rated “crisp’). Despite their similar textures, these apples were different in soluble solids, acidity, and other taste panel quality factors. At har- vest, apples with higher AOD (580-640 nm.) values (categories 4 and 5) were sweeter, less tart, more flavorful, and higher in overall quality than apples with lower values (cate- gories 1, 2,and 8). : After 6 months’ storage at 32° F., apples in AOD (580-640 nm.) categories 1, 2, and 3 were firmer than those in category 4 (rated “slightly mealy’’). The taste panel scored apples in cate- gory 5 as sweeter, less tart, and higher in over- all quality than apples in category 1, although the two categories were not different in texture (tables 1 and 2). Apples in AOD(580-640 nm.) category 3 contained the most total chlorophyll at harvest. However, the variability among samples for each category was so great that differences be- tween means were not significant, both at har- vest and after storage (fig. 7). AOD (700-740 nm.).—Chlorophyll content and AOD (700-740 nm.) values showed the fol- lowing relationship: higher AOD (700-740 nm.) value = higher chlorophyll content. After 6 months’ storage, apples in category 4 still con- tained five times as much chlorophyll as apples in category 1 (figs. 7 and 8). At harvest, apples sorted by AOD (700-740 nm.) were different in Magness-Taylor firmness and taste panel texture, ranging from less than crisp to more than crisp. Apples in category 1 (low chlorophyll) were less firm than those in the other categories. These low-chlorophyll ap- ples were sweeter, less tart, more flavorful, and higher in overall quality than apples in the high-chlorophyll category (category 4) (tables 1 and 2). After 6 months at 32° F., firmness differences between categories were larger than at harvest, ranging from slightly mealy to crisp. Firmer apples had higher AOD(700—740 nm.) values (Text continued on p. 13.) ‘9961 ‘a}ep yoArvy pue A1039}"9 (‘WU OF9-:08q) COV useMyoq diysuonefay—e aun S b “LSAAYVH Yad STAHSNG Oly “hYOO9ILWI xAYO9ILWI HIVI OLNI G3LYOS LSIAYWH 4O LNIDYId 001 06 08 OL 09 0S On O€ 02d Ol 0 x aa SO . Pete teecesene Xs ‘ee S55 RRL ras PaO as OX xxx SZ \Z TOOK SOKO Mecececacacacacatatatetete eee hehhhchs RSH HHH HHH III IVY LMM Mae PRL? 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S25 SO $055 S055 2555 5 ‘ eoshchetatatatenees § SSS SSS Caen a eocacacacee ROO RS S5052505¢5 o, SON $ 50 S2 SKS rererereenececareteeverereren SO retetaconetecononerecaten Li ° N oe) —_—= od r= nA a r+ s SS o Ww => o = So oso a 2 — Lu eeetetetatetets — LL. ) —_) © —) e) Ww a ae) ™N SilddV 05 40 % 120 80 100 60 20 40 AOD (700-740 nm.) VALUE FIGURE 6.—Distribution of AOD(700-740 nm.) values before and after 6 months’ storage at 32° CHLOROPHYLL (MGM./GM.) FREEZE-DRIED WEIGHT WAVELENGTH PAIR: @ AOD (580-640 nm) O AOD (700-740 nm) 2 3 “ ) LIGHT-TRANSMISSION CATEGORY * *® EACH POINT THE MEAN OF 30 APPLES (3 SAMPLES OF 10 APPLES EACH). FIGURE 7.—Chlorophyll content at harvest, 1966. 11 12 CHLOROPHYLL (MGM./GM.) FREEZE-DRIED WEIGHT WAVELENGTH PAIR: @ AOD (580-640 nm) © AOD (700-740 nm) 2 3 ~ LIGHT-TRANSMISSION CATEGORY * % EACH POINT THE MEAN OF 40 APPLES (4 SAMPLES OF 10 APPLES EACH). FIGURE 8.—Chlorophyll content after 6 months at 32° F., 1966. > (higher chlorophyll). Yeatman and Norris (8) reported that low-chlorophyll apples were slightly firmer than those with high chlorophyll, but they presented no statistical analyses. The correlation coefficient for panel texture scores versus Magness-Taylor firmness after storage was 7r +0.85. Although panelists showed no overall preference for any category after storage, apples in AOD(700-740 nm.) category 1 (low chlorophyll) were still rated as sweeter, less tart, and more flavorful than those in category 4 (high chlorophyll) (table 2). Neither AOD (580-640 nm.) nor AOD (700- 740 nm.) categories were significantly different in juiciness. 1967 Test Relationship Between AOD(580-640 nm.) and AOD(700-740 nm.) AOD (580-640 nm.) and AOD (700-740 nm.) values for the same apples were compared to detect any relationship between the two wave- 13 length pairs. For the 480 apples sorted by AOD (700-740 nm.), the correlation coefficient be- tween AOD (580-640 nm.) and AOD(700-740 nm.) was r = —0.80. A plot of the data showed that the negative relationship occurred across the three categories, not within a category. Using only category numbers (1, 2, or 3) in the calculation produced a correlation coefficient of ry = —0.77. Because the pigment measured by AOD (580-640 nm.) is not known at this time, explanation of the relationship between this wavelength pair and AOD(700-740 nm.) is difficult. Difference Meter Values (AOD’s) After Storage Average difference meter values for AOD (580-640 nm.) categories increased after 2 and 4 months’ storage at 32° F. The rate of increase was greater for apples in conventional storage than for those in the CA room (fig. 9). Between the 4- and 6-month tests, AOD(580-640 nm.) TABLE 1.—Laboratory results for Red Delicious apples sorted by AOD(580-640 nm.) and AOD (700-740 nm.) at harvest and after 6 months’ storage at 32° F., by category, 1966-67 3 Wavelength pair Firmness (lb. )? Soluble solids (%)8 Titratable acidity (%)8 and category Harvest 6 months AOD(580-640 nm.):4 Geet SN. 8 Re ee 13.0 e¢ Vga a a 17. Ta 13.6 b BS 17.7a 13.7 b Aner is Tete 12.5 4d jj. 5 17.7a 2s ad AOD(700-740 nm. ):4 [Rome a Mee or 16.8 ¢ 12.0 g EG al ON eS L.5b 12.5 f De a ee 18.0a nae e (slates. 2 ly 18.2a 14.6 d Harvest 6 months Harvest 6 months e 12.8 be 0.250a 0.198 e¢ e 12.4 cde 0.232 b 0.190 ed de 12.5 ed 0.235ab 0.180 d be 12.8 be 0.227 b 0.152 e a 13.1lab 0.224 b 0.148 e 4ab 13.5a 0.219 e¢ 0.144 e 6 ed 12.8 be 0.226 be 0.179 d 1 de 12.7 ed 0.240ab 0.186 d 9 e 12.8 be 0.248a 0.185 d 1 For each wavelength pair, within a quality factor, means followed by the same letter are not significantly different (5-percent level). 2 Mean of 100 measurements (50 apples). 3 Mean of 5 composite samples (10 apples each). 4 Category =20 units on 100-unit scale of difference meter. > 1=low chlorophyll; 4=high chlorophyll. 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ANY ep ge aan aes eT a?("WUU 0FL-00L) GOV oq 3°G %G 4s Or P GST 48% oq bh BOG) OGTR, MONG: near arccres ¢ Pp? 8°P qeo'g¢ dg i a oe oe a 2 poq &°p Going: 3Pis (08Gh Veiga ene races p Posh Pp? 8h are ate oq 2% Rg ap? 8's ap Lg Capa CSG) sae eae g pPLe Pp? 0G Gqoe aes oq 1°% R'E a gg op? 0'F 94 0°F BBQ | TTT Tne om tener z P Sh PL ate qoe 42'S Rg 2 Ps 2 of OGG, “Ape, sian weeeesce resco ee I z: ("UU OF9-O8S) GOV Ss sy}UOU 9 4SOAIV EY SYJUOULg = JSOAIV ET syyuow 9 4SOAIV ET Ssy{UOUW g 4SOAIV FT SyJUOULg = JSOAIB FY AI039}vd pue sed yysuapaar A UOlJOVAL [[VIBAO LOARL YT SsouyJIB], ssouyaaMs 91N4X9,L, eee 149-9961 ‘hsohazna hq “We oé& 4 abo10js ,syyuow 9 4az{p pun JSAVLDY JD (WU OFL-O0L)TOV pun (‘wu Ot9-08¢) OV fq paj.os sajddv snowyoaq pay of szjnsau qauvd ajJsvI—SZ ATAV.L values for apples in the CA room decreased sharply, while values for apples in conventional storage increased or remained the same. This decrease cannot be explained. Laboratory and taste panel tests showed no significant differ- ences between apples from the two storages. Average values for AOD (700-740 nm.) cate- gories in both storages decreased slightly dur- ing storage. All except apples in the high- chlorophyll category remained within their original category limits (fig. 10). The change from positive to negative values during storage that was observed in the 1966 test did not occur in 1967. CATEGORY CONVENTIONAL STORAGE O A CATEGORY 3 AOD (580-640 nm) VALUE CATEGORY 2 CATEGORY 1 MONTHS AT 32°F.* * EACH POINT THE MEAN OF 20 APPLES. Ficurse 9.—Average AOD (580-640 nm.) values during storage at 32° F., 1967. CATEGORY : O CONVENTIONAL STORAGE ® A a 3 60 CATEGORY 3 AOD (700-740 nm) VALUE 0 2 4 6 8 MONTHS AT 32°F.* EACH POINT THE MEAN OF 20 APPLES. FIGURE 10.—Average AOD (700-740 nm.) values during storage at 32° F. Laboratory and Taste Panel Tests Because analyses or variance showed no significant differences between apples in con- ventional storage and in the CA room, data are presented as averages of the two storages. AOD (580-640 nm.).—At harvest, apples sorted by AOD (580-640 nm.) were not differ- ent in any of the quality factors tested. Differ- ences among categories were found for some quality factors after 2, 4, or 6 months’ storage. For example, after 4 months’ storage, apples in category 3 were sweeter, lower in acid, and more flavorful than apples in category 1 (tables 3 and 4). Differences among categories were smaller and more variable than those found in the 1966 test. Firmness differences did not de- velop during storage as they had in 1966. Apples in category 1 contained more chloro- phyll than apples in categories 2 and 3 (fig. 11). These chlorophyll results support the negative 16 correlation between AOD(580-640 nm.) and the chlorophyll wavelength pair, AOD (700-740 nm.). In 1966 apples with midscale values (cate- gory 3) were highest in chlorophyll, but data were too variable for significant differences among categories. AOD (700-740 nm.).—On all four test dates, apples in AOD(700-740 nm.) category 1 (low chlorophyll) were higher in soluble solids, sweeter, and more flavorful than apples in cate- gory 3 (high chlorophyll). These low-chloro- phyll apples were scored highest in overall qual- ity in all except the 2-month test. Although taste panelists found no tartness differences at harvest, apples in category 1 were less tart than those in category 3 after 2, 4, and 6 months’ storage (tables 3 and 5). The positive relationship between firmness and AOD (700-740 nm.) value found in 1966 was not found in 1967. Magness-Taylor firmness at harvest showed category 1 (low chlorophyll) firmer than category 3 (high chlorophyll), while the taste panel scored category 3 firmer than category 1 after 2 months’ storage. For quality factors other than texture, AOD (700- 740 nm.) value at harvest seems a good indica- tor of after-storage quality. CHLOROPHYLL (MGM./GM.) FREEZE DRIED WEIGHT MONTHS AT 32°F. 0 2 mB 6 ] 2 3 AOD (580-640 nm) CATEGORY * %® EACH POINT THE MEAN OF 20 APPLES (2 SAMPLES OF 10 APPLES EACH). FIGuRE 11.—Chlorophyll content of Red Delicious apples sorted by AOD (580-640 nm.), 1967. 17 TABLE 3.—Laboratory results for Red Delicious apples sorted by AOD(580-640 nm.) and AOD (700-740 nm.) at harvest and after specified time in storage by category, 1967-1968 Wavelength pair, quality Months in storage factor, and category At harvest OO 2 4 6 AOD(580-640 nm. ):? Firmness (lb.): | alten aha Sate oat Ya ih ek 17.0a 15.8 b 14.2 de 13.4 f Pe ag bk LPN 17.0a 15.4 be 14.3 de 13.3 Gs oe ee Me hat ae 17.4a 15.9 b 14.8 ed 1A ef Soluble solids (%): 1 LO pe cy nage ee ee 11.8 e 12.2 cde 12.1 de 13.0abe ie Meee ee Se aS re ee 12.1 de 12.7abed 12. 8abed 13.1lab Giyd fe Mn eee 12.4 bede 12. 7abed 13.1lab 18.4a Titratable acidity (%): IGE cu Sees en .275a .256abe .245 ed .221 ~~ def ee .265abe .255abe .224 de . 200 ef ee .273ab .249 be 217 ef .198 f AOD(700-740 nm.):3 Firmness (lb):4 ray pe a re ee See 17.6a 16.1 be 14.1 de 13.6 ef tl Re 5 Re 17.3a 15.8 be 13.9 de ul eal Re 7 A=: eee ee ee 16.3 b 15.5 ¢ 14.3 d 13.2 f Soluble solids:4 | ee ee 12.2 cdef 12.7 be 12.9 b 13.5a se see a Lt 7 f 12.1 cdef 12.4 bede 13.0 bed See ees Pee ae Baa 11.0 g 11.9 def 11.8 ef 12.5. ad Titratable acidity (%):4 1 Up ee 271a .260a .236 be .208 d Ve 0 Lp Se .264a .258ab .226 ed .208 d See eee te on ae ae .256ab .252ab .236 be .229 ¢ 1 Mean of 4 composite samples of 10 apples each, except for firmness, that is the mean of 80 measurements (40 apples). For each wavelength pair, within a quality factor, means followed by the same letter are not significantly different. 2 Category =30 units on 100-unit difference meter scale. 3 Category =25 units on 100-unit difference meter scale. 4 1=low chlorophyll; 3=high chlorophyll. 18 TABLE 4.—Taste panel results for Red Delicious apples sorted by AOD(580-640 nm.) at harvest and after specified time in storage, by category, 1967-68 * Months in storage Quality factor and category ? At harvest 2 4 6 Texture: OD we A tin dw Er oo a APA PR coy ed 5. 5ab 5.6a 4.8 bede 5. 0abed AEDT SOE AER PE PT ar ENE iE EERE Es SS ye AG, * 5.4abe 4.7 ede 4.3 de 4.2 e Bhat ee a sae neat ee eee Soke et Se ee 5.6a 5.2abe 4.4 de 4.2 e Sweetness: Pe een te see Coane ee ae Se Dees ae 2 3.6 be 3.4 ¢ 3.8 be 356%" ¢ Die oe, Geen Bee eae eee oe Pee 2 2 ee eS 3.8 be 4.5ab 4.5ab 4.4ab Sire ae tas, eee ete See oie me aoe eee 3.9abe 4.labe 4.8a 3.9abe Tartness: OER A eo APS I re ae 3.2ab 3.5a 3.0abe 3.0abe Da a aa N a A a st es NR ve I are ta cr ae ee ee 3.2ab 2.7 be 2 A0uaC 2345ic Oe A As a wake escent ee Ee ee ete es ee 2.8 be 2.9abe 2.5 ¢ 2.4 ¢ Flavor: estes Ne ihe 2) aise tetas a es SA ens oe endl aie ce rayne aoe 3.8ab 3.4ab 3.2 b 3.7ab 7 EE SAE SPR A a Me RS TIE PRD fe ee at aE EE ee 4.0a 4.0a 3.8ab 4.0a Be pe Ss seis A Saleh er eee et tae eae 28 eee 4.0a 3.6ab 3.9a . 3.6ab Overall reaction: | Lf epee A ect ee en RR ope ots 5.6abe 4479) 0 4.8 cd 5. 4abe 7 EI AT EN Be TOT een EZ Pe Ee CE SOE 5. Tab 5. 4abe 5.4abe 5. 6abe eee eR Dee ON ore we Chee Sea SSS AME Ae eae ee Aa 5.9a 4.9 bed 5.6abe 5.2abed 1 Mean of 4 replications for 5 judges on a 7-pt. scale, except for flavor, that is mean of 5 judges on a 5-pt. scale. Within a quality factor, means followed by the same letter are not significantly different. 2 Category =30 units on 100-unit scale of difference meter. 19 TABLE 5.—Taste panel results for Red Delicious apples sorted by AOD(700-740 nam.) at harvest and after specified time in storage, by category, 1967-68 Months in storage Quality factor and category 2 At harvest Z 4 6 Texture: SIRS iy 0S 2a See ce ng ee ee 5.4ab 4.8 bed 4.5 ed 4.8 bed (OT nN OO en a 8 Fay 22 ee ee 5.2abe 5.2abe 42. oa 4.2 d 35 ONION fe he ee oe SS ee 5. labe 5.6a 4. 9abed 4. 9abed Sweetness I i ee a ES ee ee eR Se ne 3.6 bed 4.4ab 4.4ab 4.6a 7 NOI IO Se 2 Ne 7k nN ET Peis ole he 3.2 de 4.0abed 4. 2abe 4.4ab SN eres ote, NO ee Re eee ese Za e 3.4 cde 3.4 cede 3.2 de Tartness: jl ens BRA Wee ee SPS A ne ee ee ee eee 3.3abe 2.6 de 2.8 cde 2.4 e DN Sy Ste a 3.labed 3.0 bed 2.6 de 2.6 de SS a ee ee ee ee ee 3..%a 3.6ab 3.3abe 3.0 bed Flavor TU > = ee ee 3.8ab 3.8ab 4.0a 4.la ey AAI NT Rie lg ea 3.6abe 3.8ab 3.6abe 8.8ab Sere er Shs de Se A SY 3.2 ed 320 3.2 ed 3.3 bed Overall reaction: TUES I aR pS Sa Pe 5. 5ab 4.8 bed 5.6ab 6.0a Sa 5 2 18 ee apace a a ce 5.4ab 5.0 bed 5.2abe 5. 6ab SB ES a oe 4.6 cd AL? ad 4.6 ed 4.8 bed 1 Mean of 4 replications for 5 judges on a 7-pt. scale, except for flavor, that is mean of 5 judges on a 5-pt. seale. Within a quality factor, means followed by the same letter are not significantly different. 2 Category = 25 units on 100-unit scale of difference meter. 3 1=low chlorophyll; 3=high chlorophyll. 20 CONCLUSIONS AND RECOMMENDATIONS Red Delicious apples can be sorted for quality by a light-transmission measurement of in- ternal pigmentation. During the 3-year test, AOD (700-740 nm.), the chlorophyll wave- length pair, was a more reliable indicator of internal quality than AOD (580-640 nm.). The AOD(700—-740 nm.) value of an apple at harvest is related to its quality after 6 months’ storage at 32°F. However, some grow- ers may prefer bulk bin storage followed by sorting and packing immediately before ship- ment. More information is needed on the rela- tion of after-storage AOD values to after-stor- age eating quality. Because of variable conditions in the CA room, no conclusions about the effects of CA versus conventional storage on apples sorted by light transmission can be made from this study. Many laboratory and taste panel quality fac- tors were measured during the tests because “apple quality” can be defined in many ways. Few of the apples were actually “unacceptable” to the taste panel. Light transmission sorting would enable the grower to sort apples into groups that are different in specific quality factors. High-quality apples could be sold soon after harvest at a premium price, while others could be stored. The market for which the apples are intended would determine which group would be labeled high quality. Our laboratory panel preferred apples that were less firm, sweeter, and less tart. However, consumer tests on a larger scale are needed before deciding on quality labels for specific groups of consumers. In a survey on the use of selected fresh and processed fruits (4), homemakers were asked what a store manager could do to sell more fresh fruits. Almost 50 percent responded, ‘“‘Dis- play high-quality fruit.” One in four home- makers who had bought fresh fruit during the previous 12 months was disappointed with her purchases. The market for high-quality apples exists, awaiting a reliable automated measure- ment of quality. Determining the best harvest date may be another valuable application for light-transmis- sion sorting, Although the data on harvest date versus optical density difference represent only one year (1966) for one orchard of Red Deli- cious, the shift in the distribution of AOD values over a 4-week harvest period was strik- ing. More research is needed on the number of apples required for a reliable sample. From the AOD (700-740 nm.) values of a sample, a grower might decide to harvest when a large proportion of his apples fall into a defined high- quality group. As mechanical harvesting be- comes more universal, the grower could schedule his equipment in various parts of his orchards to yield the greatest return for his investment. To be a valuable and practical tool, light- transmission measurements should be reliable from year to year for many varieties in wide- spread locations. Light-transmission sorting is still in its infancy as a quality measurement. More research is needed on the variation that can be expected because of season, orchard, variety, and harvest date. Research of this type has been conducted for many years on factors such as apple soluble solids and flesh firmness. Reliable standard settings, zero val- ues, and other instrumental guidelines are necessary for a numerical AOD value to have practical meaning. (1) (2) (3) (4) 21 LITERATURE CITED ANDERSON, R. E. 1967. EXPERIMENTAL STORAGE OF EASTERN-GROWN DELICIOUS APPLES IN VARIOUS CONTROLLED ATMOSPHERES. Amer. Soc. Hort. Sci. Proc. 91: 810-820. BirTH, G. S., and Norris, K. H. 1965. THE DIFFERENCE METER FOR MEASURING IN- TERIOR QUALITY OF FOODS AND PIGMENTS IN BIOLOGICAL TISSUES. U.S. Dept. Agr. Tech. Bul. 1341, 20 pp. ——— and OLSEN, K. L. 1964. NONDESTRUCTIVE DETECTION OF WATER CORE IN DELICIOUS APPLES. Amer. Soc. Hort. Sci. Proc. 85: 74-84. CLAYTON, L. Y. 1966. HOMEMAKERS’ USE OF AND OPINIONS ABOUT SELECTED FRUITS AND FRUIT PRODUCTS. U.S. Dept. Agr., Mktg. Res. Rpt. 765, 78 pp. (5) Norris, K. H. (6) (8) 1958. MEASURING LIGHT TRANSMITTANCE PROPER- TIES OF AGRICULTURAL COMMODITIES. Agr. Engin. 39: 640-651. OLSEN, K. L., SCHOMER, H. A., and BARTRAM, R. D. 1967. SEGREGATION OF GOLDEN DELICIOUS APPLES FOR. QUALITY BY LIGHT TRANSMISSION. Amer. Soc. Hort. Sci. Proc. 91: 821-828. SIDWELL, A. P., BIRTH, G. S., ERNEST, J. V., and GOLUMBIC, CALVIN. 1961. THE USE OF LIGHT TRANSMITTANCE TECH- NIQUES TO ESTIMATE THE CHLOROPHYLL CON- TENT AND STAGE OF MATURATION OF ELBERTA PEACHES. Food Technol. 15: 75-78. YEATMAN, J. N., and Norris, K. H. 1965. EVALUATING INTERNAL QUALITY OF APPLES WITH NEW AUTOMATIC FRUIT SORTER. Food Technol. 19: 123-125. yrU.S. GOVERNMENT PRINTING OFFICE: 1972 0—444-564 i Bret eae “in one x ih a) is