A STUDY OF MATURITY INDICES
FOR HALEHAVEN PEACHES
DISSERTATION
Presented in Partial Fulfillment of the Requirements for
the Degree Doctor of Philosophy in the Graduate
School of The Ohio State University
By
Surinder Singh Attrl, B. A,, M. S.
******
The Ohio State University
1959
Approved by
Adviser
Department of Horticulture ACKNOWLEDGMENTS
Throughout the course of this study the following people have materially aided the author* In acknowledgment of their help and the value of their association* the author wishes to express his appreciation*
To Dr* Freeman S* Hewlett, Chairman* Department of Horticulture* for his invaluable advice* criticism* and suggestion in the writing of this dissertation* and particularly far his guidance and one ouragement •
To Professor Donald Comin* who has given freely and willingly of his time* interest* guidance* and advice*
To Dr* C* R. Weaver* Statistician* Ohio Agricultural Experi ment Station* for his interest and assistance in the statistical analysis of the data*
To Jfr. Harold S* Steamer, whose co-operation and assistance in operating the equipment used for this work has materially aided the author*
Surinder Singh Attri
ii TABLE OF CONTENTS
Chapter PaC°
I. INTRODUCTION...... 1
II. REVIEW 01'’ LITERATURE...... 4
A. Teminolo^' of Maturity...... 4
1* ihturo and its Derivatives...... ••••.••••..••.*4
2. lUpe and its Derivatives ...... 5
B, Indicos of Maturation, ...... 6
1, Color...... ,••••...••6
2, Pressure...... •••««••». ,.•••...... £
3, Soluble Solids...... ••..•••,..10
4* Acidity, ...... ••••...... ,,10
5. Ifcrdrogen Ion Concentration...... 11
6. Index Humber...... *...... 12
7. Soluble Solids/Acids Ratio,...... •••••12
T, Cliloropliyll ...... 13
9. Carotono and Carotonoids,.,.••.•••..,••••••••••13
III. MATERIALS AND METHODS...... 14
A. Firmness Tests,, .... •••••.••.... .,,17
1, Test with the Durcmeter,.•••••••••••.... 17
2, Test with the Ka^ness-Taylor Pressure Tester...lc
D. Color Tests...,.•••...... ,...... IT
1. Subjective...... ••••*..... Id
2, Objective...... 19
Hi C. Chemical Tests*...... *...... *...... 20
1* Soluble Solids *.... *...... 21
2. hydro^on Ion Concentration...... 21
3. Total Titratablo Acidity...... *...... 21
4. Index Number...... 21
5. Soluble Solids/Acids Ratio...... •••*21
6* Clilorophyll content...... 22
7. Carotene Content...... *...... 22
IV. RESULTS...... 23
A* Firmness Tests...... 23
1* Test with the Durcmeter...... *...... 23
2, Test with the tfagnass-Teylor Pressure Tester...26
3. Color Tests...... 20
1. Subjective Tests...... •••••■••28
2. Objoctlve Test...... 35
C. Chemical Tests ...... ••••••••51
1. Soluble Solids Percentage...... 51
2. Ifrdrogen Ion Concentration...... 56
3. Titratable Acidity Percentage...... 61
4. Index Number Test...... ••••...... 65
5. Soluble Solids/Acids Ratio...... 71
6. Chlorophyll Content Test...... •••••76
7. Carotene Content Test...... •••••••••••••...... 81
iv V. DISCUSSION OF RESULTS...... 86
A. Maturation Phase.. *...... •••••86
1. Physical Indices...... 86
2. Chemical Indices ...... 90
B. Storage and RipeningPhases ...... 95
1. Physical Indices...... ,95
2. Chemical Indices...... 96
C. Correlation of Magness-Taylor Pressure Tester
with Other Indices ...... ••*••••••••99
D. Other Correlations...... •••••••..... 100
1. Indices with Descending Linear Regression Curves...... 100
2. Indices with Ascending LinearRegression Curves...... l00
3. Indices with an Initial Fall Followed by a Rise...••• .101
4. Indices with an Initial Rise Followed by a Fall...... 101
5. Negative Correlations...... ••••••101
E. Suggested Indices...... •*••••••..... 102
1. Ratios of Color and Firmness...... 102
2. Ratios of Color and Titratable Acidity...... 103
VI. SUMMARY AND CONCLUSIONS...... 1°5
LITERATURE CITED...... 107
AUTOBIOGRAPHY...... 112
v LIST OF TABLES
Table Page
1* Harvest dates far each stage of maturation during August 1957 and August 1953 seasons .... •••••14
2, Tentative pressure test ranges of maturity of Hale- haven peaches suggested by Craft (11)•• ••••••.... ••••.... 16
3. Dur erne ter firmness values of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1953..... •••••••••...... 24
4* Migness-Taylar firmness values of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1953*••••••• ...... •••26
5* USDA Color Chart values of Halehaven peaches at eight stages of maturitlon prior to harvest and after storage during 1957-1953...... •••••••29
6. Upshall's Peach Chart values of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1958...... ••••...... 32
7. Gardner-Hunter meter color values of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1953...... 36
8* Refract cine trie soluble solids percentages of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1953...... ••••••••••.... •••52
9. PH values of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1958...... 57
10« Titratable acidity percentages of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1958*.••...... 61
11. Index numbers of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1958...... 66
12. Soluble solids/acids ratios of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1958...... 72
vi 13. Chlorophyll contents of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-195#...... 77
14* Carotene contents of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1958...... 82
vii LIST OF ILLUSTRATIONS
Figure Page
1. Regression of Durcmeter firmness values of lot a in 1957 and 1958...... 25
2. Regression of Magness-Taylcr firmness values of lot a in 1957 and 1958...... 27
3. Regression of USDA Color Chart values of lot a in 1957 and 1958...... 30
4. Regression of Upahall'a Peach Chart color values of lot a in 1958...... 33
5. Regression of Upahall'a Peach Chart color values of lot b in 1958...... 34
6. Color diagram showing the relationship of Gardner* Hunter "a* and "b* scales to visual color...... 37
7. Regression of Gardner-Run ter "Rd" values farlot a in 1957 and 1958...... 38
8. Regression of Gardner-Hunter Ma" values for lot a in 1957 and 1958...... 39
9. Regression of Gardner-Hunter "b* values far lot a in 1957 and 1958...... 40
10. Regression of Gardner-Hunter "a/b" values far lot a in 1957 and 1958...... 41
11. Regression of Gardner-Hunter "a" valuesfor lot b in 1958..... 43
12. Regression of Gardner-Hunter " W values far lot b in 1958...... 44
13. Regression of Gardner-Hunter "Rd" values forlot c in1958 ...... 45
L4. Regression of Gardner-Hunter "a" values forlot c in 1958...... 46
15. Regression of Gardner-Hunter "b" valuesfar lot c in 1958.,.,,.47
16. Regression of Gardner-Hunter "a/b" values for lot c in 1958.,..48
17. Color diagram of Gardner-Hunter "a" and *bN valuesfar lot a in 1957 and 1958...... 50
viii 18. Color diagram of Gardner-Hunter "a" and "b* values far lots b and o In 1958...... 50
19* Regression of soluble solids percentages for lot a In 1957 and 1958...... 53
20.Regress!on of soluble solids peroentages for lot c in 1957..... 55
21. Regression of pH values far lot a in 1957 and 1958...... 58
22. Regression of pH values far lot b in 1957*...... 59
23. Regression of pH values far lot c in 1957 and 1958...... •••..60
24* Regression of titratable acidity far lot a in 1957 and 1958....62
25. Regression of titratable acidity far lot b in 1957 and 1958.••.63
26. Regression of titratable acidity for lot c in 1957 and 1958.*•.64
27. Regression of Index numbers far lot a in 1957 and 1958.....67
28. Regression of index numbers far lot b in 1958... ..68
29. Regression of index numbers for lot c in 1958...... 69
30. Regression of soluble solids/acids ratios far lot a in 1957 and 1958...... *.... .•••*».... 73
31. Regression of soluble solids/acids ratios far lot b in 1957 and 1958...... 74
32. Regression of soluble sollds/aclds ratios far lot c in 1957 and 1958...... 75
33. Regression of chlorophyll content far lot a for 1957 and 1958..79
34. Regression of carotene content for lot c far 1957 and 1958..... 85
ix 1
I. Introduction
The purpose of this study was to adept and evaluate the matur ity indices used on other fruit orops as objective indices of Hale haven peaches* Increasing production of peaches in the United States in recent yearo has accentuated problems of harvesting, handling, and marketing peaches*
Peaches begin to undergo deterioration in quality as soon as they ripen* A tree-matured peach has shorter life remaining than one picked at an earlier stage* Peaches may be sold to the consumers in or near the orchard or they may be sold after shipping considerable distanoe from the point of production* The stage of maturation at which peaches are picked is of consequence to growers, distributors, and consumers* The grower requires marl mum tannage with minim® harvesting expense* The distributor is interested In peaches which will stand handling and shipment with little bruising and spoilage*
The consumer desires a high quality peach*
Thus lack of information on the part of the producer and his desire to cut harvesting costs by a minimum mmbar of harvests, and the desire of the distributors to avoid bruising and to fill early orders cause peaches of several stages of maturation to reach re tailers* Hartman *s (23) study shows that ripeness was the main factor affecting peach sales* To achieve the goal of consumer satis faction, peaches must be picked at the right stage of maturation*
When unripe peaches are marketed, both the seller and the con sumer suffer* The seller does not always reoeive a fair prioe and the oonaunar does not obtain a good produot* I mature peaches do not 2 ripen to a desirable quality and flavor, aa is clear fran the work of
Fisher, Britton, and 0*Reilly (18), Ha via (24), Ccmin (9), Opehall (14),
Culpepper (14), Neubert ai gl* (30), Matsmota (28), Haller and
Harding (22), Davies (15) and many others.
According to Fisher and Britton (17) peachea increase In volume approximately 4 percent dally during the week before opti mum harvesting maturity. They estimated a total gain in volume fran
20 to 39 percent during this period. This study agrees with that of
Haller (21), whose statistics on the Increase in volume during this week were gathered from other studies. There seems to be, therefore, an average increase in volume of two to six percent a day. These authors stressed the desirability of harvesting as late as possible to obtain maximum volume. Premature picking involves a heavy loss in tonnage.
Although some Investigators attesipted to establish indices of stages of maturation, they often limited their studies to two or three stages of maturation, such as "green," "firm," and "mature." The precise purpose of the study reported herein was to study changes occurring just prior to maturity. Some maturity studies have been conducted on ELberta peaches, but very little work has been carried on so far on Halehaven peaches. The variety Halehaven was therefore chosen for this study. This study has therefore been carried on with the following objectives: (1) To study the changes within
Halehaven peach frulta during a period from a few days before maturity until maturity and also while the fruits were in storage, and (2) to evaluate certain other Indices used on other crops for possible adaptation to Halehaven peaches. u
II* Review of Literature
It was useful in this study to review the work that had already been canpleted.
A. TaraHnolctav tfcturity
A study of the literature reveals considerable variation in the terminology used to describe maturity and ripeness*
Cbe investigator, Lott (27), based the terminology on the fact that fruit attached to the plant is in a physiologically distinct environment from the fruit after harvest* This attempt to utilise suitable terminology for the developmental processes occurring in fruit attached to the plant as opposed to changes after harvest has a sound physiological significance* The present writer prefers to use
Lott's (27) recommendations for the terms "mature," and "ripe" described below, although they are not perfect!
1* Mature and its derivatives
a* Mituret That stage of fruit development which will insure the attainment of maximum edible quality at the completion of the ripening process* Only fruit which is mature at harvest can attain marl mum edible quality, that is, become ripe*
b* ffeturityi The condition of being mature* There is only one stage of maturity, that at which the fruit is mature*
Therefore, stages or degrees of maturation should be referred to, not stages or degrees of maturity*
c. Maturation! The developmental process by which a fruit attains maturity* 5
d. Optimum maturation* Since the method of handling the fruit after harvest affects the rate of the physiological changes, it is desirable to use this term with a qualifying statement concerning the method of handling.
e. Post-maturation t Changes occurring in the fruit after it has reached maturity, but while it is still attached to the plant.
This is most frequently encountered in the soft fruits and is characterized by extreme softness, evidence of tissue breakdown and deterioration in flavor.
f. Over-mature and over-maturity i Usually used to mean the same as post-mature and post-maturity.
g. Imnaturet Any stage of development preceding the attainment of maturity.
h. Immaturityj The state or condition of being Immature.
1. Greeni The term has been used frequently to designate immaturity• When used for this purpose its meaning is too ambiguous to have any real value. It is recommended that whenever it is used, it is to be described in terms of its three attributesi hue, value, and chroma.
2. Ripe and its derivativesi
a. Ripe i The condition of maximum edible quality attained by the fruit following harvest.
b. Ripenesst The condition of being ripe.
c. Ripenings The post-harvest physiological process by which the fruit attains ripeness. If the fruit is mature when har vested, ripening proceeds to ripeness; if the fruit is immature when 6
harvested, ripening cannot proceed to ripeness, but only to sons stage
of ripening*
d. Ripeni To undergo ripening! also to place in a ripening
environment*
e* Post-ripening* Changes occurring in the fruit after it
has reached ripeness*
f. Over-ripe and over-ripeness i Usually used synonymously with post-ripe and post-ripeness.
g* Unripe: Not ripe, either because ripening has not progressed long enough or because the fruit was immature when harvested and can not, therefore, attain ripeness* In general this is true* However, conditions can occur, such as varietal differences, when the fruit attains ripeness but not edible quality.
h* Unripenessi The state or condition of being unripe*
B* Indices of Maturation
Indices of maturation have been the subject of considerable research* Literature review of indices of peaches used in this study is given below:
1* Color
Blake si ai* (5) reported that fruit growers generally determine the stage of maturation of peaches by the ground or under
color of the fruit* Haller (21) stated that as peaches approach maturity, the leaf-green ground color changes to a lighter shade of green* Simultaneously, a gradual yellowing, starting on the sides exposed to the light, takes place* As the peaches become mature on
the tree, a deep orange yellow develops on yellow-fleshed varieties, 7 while yellowish-white develops on white-fleshed varieties. Changes in ground color continue during ripening after the fruit has been picked. Deeper shades of yellow or orange usually develop in fruit picked at an advanced stage of maturation. The rate of change is proportional to the rate of ripening and is more rapid at higher temperatures.
Fisher and Britton (17), who conducted maturity and storage studies with peaches, reported that flesh color varied fran greenish- yellow in immature fruits to orange in mature fruits. Peaches with maturation satisfactory for shipment showed yellow skin color and orange-yellow flesh color. They concluded that skin color (associa ted with flesh color and firmness) was a reliable index to maturity«
Coe (8) presented six colors, ranging from groen to sulphur- yellow to MLrabelle and intermediate 3hades, as a guide to peach harvesting. Fisher, Britton and (^Reilly (IS) determined shades of akin color and flesh color of mature and immature peaches according to Kidgway*s color chart. These colors varied slightly in two seasons for given varieties. Such colors as amber yellow, barium yellow, straw yellow and reed yellow were characteristic of mature peaches. There was a close similarity between skin color and flesh color in any given variety.
Culpepper (14) suggested that color is a dependable guide in judging maturation, but he warned that cool, sunless and rainy weather could cause the peaches to be soft while they are still green. Croce (13) maintained the point that color affords a I rough guide to the stage of maturation, although It is Influenced by variety and environment. White-fleshed varieties may be pioked when the undercolor begins to change to yellow or cream. The yellow varieties are mature when the color has reached a yellowish shade.
Bedford (4 ) stated that ground color can be used as a guide to the stage of maturation for harvesting, provided it is checked against firmness in each season and each orchard.
The above discussion indicates that color is an Index to the stage of maturation, but there are various problems connected with the use of this attribute. The growth status of the tree, varietal color differences, Intergradations of color shades in many fruits and on a single fruit, variations of color fran orchard to orchard and from year to year, and weather conditions— all make it difficult to use color alone as an index to the stage of maturation of peaches.
2. Pressure
Pressure tests have been used by various workers to determine the degree of maturation of peaches. Blake $£ ai. (5), summarising their study on the development and ripening of peaches, stated that pressure tests indicate that the firmness of peach flesh varied in versely as the rate of growth. Fisher and Britton (17) presented data showing that mature fruit had a considerably lower pressure test than immature fruit. However, a great variability in firmness was nbted among fruits in the same sample, and even between the cheeks (sides) of the same peaoh.
Culpepper (14) found that the pressure test results of coexoercial eastern peaches coincided with those obtained by visual and manual 9 examination. Both tests Indicated a progressive softening of the tissues during maturation. Havis (24) found firmness determined by a pressure tester as a reliable basis far rating maturation. Simpson
(31) also advocated pressure tests far determining the stage of matur ation. According to her, resistance of the flesh to a penetrating plunger was a reliable field index of maturation for peaches in certain areas and climates.
Willison (37) decided that the pressure test gave the most reliable indication of the stage of maturation. Although the pressure test gave more accurate results at very immature stages and at maturity than during the intermediate stages of maturation, its application at the last mentioned stage was more satisfactory than all other methods employed, among which was the color test. Morris (29); who related peach maturation at harvest to quality; declared that a combination of a pressure test and a color test seemed to be the best method of devel oping a standard for ascertaining the stage of maturation.
Haller (20); in his study of the application of pressure tests to several fruits; reported that the firmness or pressure test cannot be used as an index to the stage of maturation of peaches except to indicate the color of fruit that should be picked. According to
Cardlnell and Barr (7); pressure tests cannot be used independently of other methods in determining harvest dates or selection of fruitto be picked. They can, however; often be used to determine the color standards far each picking. 10
3* Soluble Solids
According to Allmendlnger (2), soluble solids increased about 30 percent with the Elberta and about 22 percent with the J* H.
Hale between shipping and canning stages of maturation. According to
Allen (1) there appeared to be only a slight gain in soluble solids after picking peaches* Neubert si fil* (30) found only slight differences in total and soluble solids of peaches at various harvest maturations,
Fisher and Britton (17) noted that the soluble solids content
increased in all peach varieties tested as they approached maturity.
But they were of the opinion that increase in soluble solids was not a satisfactory index of the stage of maturation because the range between mature and inmature fruit was too narrow. In another study
Fisher, Britton, and O'Reilly (18) again noted that differences in
soluble solids content of mature and isnature peaches were too small
to make this test of value as an index of maturation. Similar obser vations were made by Uilllson (36) and O'Reilly (31).
4. Acidity
The literature shews that acidity tended to decrease with the progress of maturation. According to Allen (1), the percentage
of acid in the flesh of peaches usually varied between 0,5 end 1.0
percent. In most oases there was a gradual decrease in acidity with
approaching maturity. A small decrease continued following harvest,
but this did not reach its minimum until the fruit had passed its
prime eating condition. These data agreed with the results of
Blake (5), which indicated that during the ripening stage. 11 titratable acidity of fruits decreased and reached a m-tMimrm ^ BOft_ ripe peaches* Because of the rapid respiration talcing place In nearly ripe peaches, the consumption of acids exceeded their pro duction*
Culpepper and Caldwell (14) likewise stated that there was In all cases a distinct decrease in acidity in all varieties during ripening*
The decrease was typically rather slow as the fruit passed from the hard-green to the shipping stage, and, in a few cases, there was a slight Increase during this period* After the fruit passed the shipping stage, the decline became increasingly mare rapid with the progress of softening* Neubert (30) concluded that the total acid content of the fruit decreased as it became more mature on the tree* Decreases in acidity were also found far fruits ripened after picking when six or mare days were required to reach the canning- ripe stage, but these decreases were not as great as occurred during fruit maturation on the tree* Fruit requiring less than aim days to ripen showed little loss in acid during ripening after harvest*
5* Hydrogen Ion Concentration
The literature indioates that pH values possibly rose as maturity was approached* The results of Neubert £& £l* (30) shoved that the pH values increased as the fruit developed on the tree and also during ripening after picking* According to Simpeon's (33) results, pH measurement showed slight promise as an index to the
stage of maturation* 12
6* Index Number
The ratio of dissociated aoids to total acids is called the dissociation constant or the index number* There are only a few references to the "index number" as a criterion of picking maturation*
According to Blake and Davidson (6 ), Du Toit and Reynake showed conclusively that there was a relation between the keeping quality of fruits and the ratios of dissociated acids to total aoids present, called the "index figure." They believed that the index figure "represents the balance between the accumulative and destructive tendencies and therefore that point at which a fruit has reached its susmit of perfection*" Camin and Sullivan (10) believed that the degree of dissociation of the hydrogen ion in
Some Beauty apples may control complex equilibria within fruit which in turn might govern the amount of pectin, sugar and acids*
They, however, considered that the evidence was still meager*
7* Soluble Solids/Acids Ratio
In his work on the voolliness of Peregrine peaches, Reyneke
(32) found that the soluble solids/acids ratio of the juice decreased during early fruit development and thereafter increased rapidly until maturity was reached* Similar fruits grown under identical conditions revealed that the soluble solids/acids ratio is an accurate basis for expressing maturation in a quantitative manner* Upehall and
Haarlem (34), in work done at the Ontario Horticultural Experiment
Station, observed that for the most part the sugar/add ratio did not change appreciably while the fruits were softening in 13
storage at 65 degrees F. A notable exception, however, vaa the
Italian prune, in which the increase in sugar content was considerable*
8. Chlorophyll
The only reference pointing to the anoint of chlorophyll
as an index to maturation is that of Kramer jfc (25), These
investigators, using the spectrophotonetric method for the measure ment of chlorophyll in the fruit flesh, obtained data tending to
validate the assumption that a loss in green pigment is an indication
of the maturation of peaches* Every delay in harvest caused a
substantial reduction in green pigment concentration, as measured
by the spectrophotooetric and fluarometric methods*
9. Carotene and Carotenoids
The results of Neubert (30) over a two-year study
of peaches showd that the total car ctenoid content of all peaches
increased through the maturing period* All peaches showed an increase
in crude carotene and total car ctenoid content during ripening after
harvest • The amount of Increase was greatest in fruit requiring the
longest time to ripen* Crude carotene of ripened fruit of all harvests
accounted for an average of 67 and 69 percent, respectively, of the
total carctenoid content of Elberta and J* H* Hale* I11* Materials and Methods
Samples of Halehaven peaches for this study were picked at intervals from the middle to the end of August in 1957 and 1958 fran the orchard of the Department of Horticulture of the Ohio
Agricultural Experiment Station, Wooster, Ohio. The maturation of the peaches at the various harvests ranged fran 7 days to 0 days to maturity, according to a pressure test. Harvests were made on different days. Usually fruits of one or two stages of maturation were collected at once in order to allow sufficient time for the detailed measurement and analysis of each harvest.
The dates of harvesting samples are shown in Table 1.
TABLE 1.-Harvest dates for each stage of maturation during August 1957 and August 1958 seasons
Stage of Maturation 1957 1958
7 days to maturity 10 14
6 days to maturity 10 15
5 days to maturity 12 18
4 days to maturity 12 19
3 days to maturity 13 20
2 days to maturity 17 21
1 day to maturity 19 25
0 days to maturity 22 29 15
These stages were determined far experimental purposes by a
Magness-Taylar pressure tester with a 5/16 inch diameter plunger.
The range in firmness and maturity of eastern-grown peaches at har vest and time required far them to ripen at room temperature, as pro posed by Craft (12), were used as guides to collect the samples.
Craft Indicated that the mare mature the peaches were at harvest, the shorter was the period required far ripening after harvest. Thus, the time required far peaches to ripen after har vest Is a good measure of their maturity at harvest. With this hypothesis Craft (12) studied the time required far peaches to ripen after harvest to distinguish peaches that were mature when picked from those that were not. From his results he constructed a table for each variety denoting the range in pressure-test readings for peaches requiring different lengths of time to ripen. His tenta tive standards for maturity of Halehaven peaches were used In this study far gathering samples. These standards are given In Table 2. 16
TABLE 2•-Tentative pressure test ranges of maturity of Halehaven peaches suggested by Craft (11)
Days to ffcturity Pounds Pressure, Mtgness- Taylor Tester
8 / A 6 . 5
8 16.5-16.0
7 15
6 U
5 13
A 12
3 11
2 10
1 10-2
0 Under 2
Peaches from several trees were pressure-tested with a
Magness-Taylar pressure tester* The color of these peaches was noted visually. Based upon pressure and color of these tested specimens, samples were then collected by the sense of touch and sight to correspond as closely as possible with the tested specimens.
In this way approximately 200 fruits of each stage of maturation were obtained in field baskets. After repeated sorting and checking in the laboratory, 90 fruits of each maturation stage were selected. 17
These samples were divided into three lots of 30 fruits each.
These lots (a,b,o) were treated as followsi
Lot a was analyzed Immediately.
Lot b was stored at 70 degrees F. until ripe when these samples were analysed in the same way as the samples of lot a.
Ripening of these samples was determined as follows t Each day peaches were inspected in storage, with their condition studied by personal judgment aided by appearance. Peaches about as soft as those of the 0 days to maturity stage of lot a were considered ripe.
Lot c was stared at 42 degrees F. for 9 days, then stared at
70 degrees F. until ripe. Ripeness was determined In storage in the same way as with peaches of lot b.
The following tests were performed on each lot:
A. Firmness Tests
1. Test with the Durometer
The Durometer type "OO," manufactured by the Shore
Instrument and ftuiufacturlng Company, Inc. for testing the hardness of rubber, was used on peaches to test its dependability as an index of firmness and maturation of peaches. Two tests per peach
(i. e., one test per cheek) were made. The total values of all the 30 peaches of a lot were averaged. The average firmness readings for the different stages of maturation (i.e., 7 days,
6 days, 5 days, A days, 3 days, 2 days, 1 day, 0 days from maturity) in each lot were compared to see hew the firmness 18 of the peaches varied with the stage of maturation and with storage.
2. Test with the Jfegness-Taylor pressure tester
Tests on each cheek of the peach were made using a
Magness-Taylor pressure tester with a 5/16 Inch tip. Two Msgness-
Taylor pressure testers were used, one with a 1 to 30 pound range and the other with a 0 to 10 pound range. The latter gives mare accurate figures with softer fruit. The total values of all the
30 peaches of a lot were averaged.
B. Color Tests
1* Subjective
a. Test with the USDA Color Chart
A Standard Ground Color Chart for Apples and Pears in
Western States issued by the U. S. Dept, of Agri. Bureau of
Plant Industry was used. This chart was used in 1957 and 1953*
The USDA Color chart has four colors, described on the chart as shade nunber 1, shade nvmber 2, shade manber 3 and shade number 4 .
The greenest part of each peaoh was matched against the chart until a shade was found that corresponded with the color of the peach.
b. Test with Upshall's Peach Chart
A color maturity chart for peaches proposed by
Upehall (34) was used. This chart was used in 1953. Its three colors came from two sources. 19
Color 1* Maer* and Paul* Dictionary of Color. 19J1.
Color 2. Horticultural Color Standards. 601/2.
Color 3. tfcera and Paul. Dictionary of Color. 10J2,
The procedure for matching the peach with the chart was the same as that far the USDA Color Chart. The color of the 30 peaches in each lot was obtained, recorded, and averaged.
2. Objective Test with the Gardner-Hunter Color and Color
Difference Meter
Since the measurement of ground color without the use of special instruments is at best partly subjective, an examination of the color of the peaches was made with a Hunter Color and Color Difference Meter.
The instrument is a tristimulus colorimeter measuring color on three scales to determine either the color difference between two objects or the color of an object relative to a standard.
In operation, the color difference meter compares an unknown specimen with standards of pre-determined color characteristics. The instrument gives three numbers for each color measured. Oh the right- hand dial is given either Rd (45 degrees luminous reflectance) or L
(visual lightness), depending upon the type of measuring circuit selected by the user. The other two scales of the instrument measure
"a," which is redness when plus, gray when aero, and greenness when minus; and "b,” which is yellowness when plus, gray when aero, and blueness when minus. 20 In this stu Gardner-Hunter*s Color and Color Difference Meter were used for measuring the color of the peaches* The Instrument was calibrated against a standard before beginning the measurement of the color of the peaches. After measuring the color of 15 peaches (i.e.,half the num ber in a sample), the Instrument was again calibrated against the standard* This procedure was followed throughout the work in both years* The greenest part of each peach was put on the aperture far taking the reading* Peaches of each stage of maturation in each lot were read in this Instrument for color in both years. Their values in the three scales were recorded* All the 30 peaches in each sample were read in the instrument with each scale and their average was taken* From the values on scales a and b for a particular stage of maturation, the ratio a/b was calculated* This was calculated for each stage in each lot and in both years to see if there was any specific trend in the values of a/b* Some variability in color was noted between fruits in the same sample* This,however, was assumed to have been reduced in averaging* The average was therefore considered as the test of the sample* C* Chemical Tests After the physical tests the skin was peeled from the cheeks of the peaches and slices were taken* Hie slices fran the 30 peaches were mixed and a composite sample of 100 grants was weighed* From this sample Juice was expressed by a Carver laboratory Press at 5,000 pounds per square inch* The juice was used for the tests on the solu ble solids, hydrogen ion concentration,and total tltratable acidity* 21 1. Soluble Solids A feu drops of the juice were placed in an Abbe refractro- meter and the percentage of soluble solids vas determined* In this way peaches of the different stages of maturation in each lot were analysed for soluble solids. 2. Hydrogen ion Concentration (pH) Frcm the juice a sample of 10 ml. was taken in a beaker and diluted to 200 ml. with distilled water. The pH was then read in the Beckman pH meter. 3. Total Titratable Acidity The amount of 0.1 NaOH required to titrate the titratable adds in the 10 ml. juice sample was determined. The amount of NaOH used in titration determined the percentage of titratable add s in the sample of juice with the following formula. Total titratable add s are reported as percent Maleic adds. N(NaOH) x ml. NaOH x 0.067 x 100 Percentage of titratable acids- ml. juice A. Index Number The index number was calculated for each degree of maturation of peaches in each lot frcm the data on pH and titratable acidity. A definite trend was sought In the index numbers frcm one stage of matura tion to another. Any trend would indicate a possible index to the maturity of peaches. 5. Soluble Solids/Acids Ratio From the figures on soluble solids and titratable acidity, the soluble solids/adds ratio was calculated for each degree of 22 maturation of peaches in each lot. Like the index number this factor (soluble solids/acids ratio) had the advantage that no further test on peaches was needed. 6. Chlorophyll Content The procedure for extracting chlorophyll described In the Official Methods of Analysis of the Association of Official Agricult ural Chemists (3) was used. A ccmposlte sample of 50 grams was ob tained from 30 peaches by taking thin slices under the greenest part of the skin. From this sample chlorophyll was extracted and made to volume in a 100 ml. volumetric flask. From this flask a sample of about 10-15 ml. was taken in a test tube and the percentage of light trans mission was calculated through it in an Evelyn Photoelectric Colori meter using a 6600° A filter and using ether as the solvent standard for 100 percent light transmission. In this way the percent light transmission of the chlorophyll solution of each stage of maturation of peaches in each lot was determined. 7. Carotene Content The procedure given in the Official Methods of Analysis of Official Agricultural Chemists (3) was used for extracting carotene. Carotene was extracted from the peaches and made to volume in a 100 ml. volumetric flask. From this 100 ml. flask a sample of about 10-15 ml. was taken in a test tube and the percentage of light transmission through it was calculated in an Evelyn photoelectric colorimeter using a 4200° A filter and using Skellysolve B as the solvent stan dard for 100 percent light transmission. IV. Results After the results were analysed statistically significant data were fitted into the regression equation. The values for the calculated regression line (best fitted line) were determined and then utilized for the interpretation of data. However, in the tables both the means of the actual numerical values (denoted by the abbreviation A) and the values for the calculated regression line (denoted by the abbreviation C. R.) have been shown. Regression curves were also constructed to illustrate the results. Only the means of the actual figures have been shown in the tables for data with no significant regression and no curves were constructed. This section contains tables for the numerical values obtained with each index. Each table is subdivided according to lot for easier ocaparison of storage changes. Years and stages of maturation are Indicated as well. A. Firmness Tests 1. Test with the Durometer Table 3 shows the average firmness readings with the Durometer for each lot In both years. 24 TABU l.-Duraneter firaneas valuea of Halehaven peaohes at eight stages of saturation prior to harvest and after storage during 1957*1958 Average Durcneter Readings (Kg./cs£ x 157*5) Year Lot A or Days to Maturity CR 7 6 5 4 3 2 1 0 1957 a A 90.4 86.4 83.3 81.2 78.8 75.1 - - 1957 a CR 89.3 88.9 84.0 81.1 78.2 75.3 - - 1958 a A 95.0 94.2 92.7 91.8 92.4 89.5 85.2 79.1 1958 a CR 96.9 94.9 92.9 91.0 89.0 87.1 85.1 83.1 1958 b A 72.7 69.8 69.5 70.7 66.4 68.9 70.5 - 1958 c A 70.2 64.2 65.6 70.7 68.3 71.5 75.6 73.9 25 The firmness values decreased as the peaches passed frost 7 to 2 days to maturity in 1957 and frcm 7 to 0 days in 1953 (Figure 1). Dwtaitir fast t*t (a) Taara 1 » 7 aai 19>* *• Nilnnljr Fig* 1.-Regression of firmness values in the successive stages of maturation of peaches* Broken lines Indicate the actual values* Solid lines show the values far the best fitted line* Readings on 1 day and 0 days to maturity were not taken In 1957 since these two stages were too soft to show differences In firmness* Each stage of maturation gave a different firmness reading with the Duro- meter of 1958 from that of 1957* Evidently peaches were relatively firmer in 1958 than In 1957* 26 Table 3 also shows Duranoter readings rn peaches stored under conditions of lot b (room ripened peaches) and lot c (cold stored and room ripened peaches)* As these peaches had undergone softening and were ripe when tested, no significant regression was found. 2. Test with the ltogness-Taylor pressure tester Table 4 represents the average pressure test readings for the lots in both years. TABLE 4.-Magnes8-Taylor firmness values of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1958 Average Pressure Readings (Pounds pressure, using 5/16" plunger) Year Lot A or Days to Maturity CR 7 6 5 4 3 2 1 0 1957 a A 15.6 14.6 11.8 11.1 11.0 4.9 3.9 0.7 1957 a CR 15.5 14.3 12.8 11.1 9.0 6.5 3.7 0.6 1958 a A 16.2 14.1 13.7 12.2 11.8 10.0 3.5 1.5 1958 a CR 15.3 15.0 14.2 12.8 10.8 8.3 5.1 1.3 1957 b A 2.3 2.1 0.6 0.8 2.5 1.1 1.1 - 1958 b A 1.5 1.6 1.3 1.4 1.3 1.2 1.1 - 1957 c A 1.8 1.6 1.5 1.5 1.3 1.3 1.0 0.4 1958 c A 1.4 1.1 1.4 1.3 1.4 1.6 1.3 1.0 27 Data on lot a (fresh peaches) In Table U reveals that the pressure test values decreased with maturation. Statistical analysis showed a significant regression in both years. The decrease in firmness, accelerating with maturation, is well-defined in Figure 2. LetWefaeee-Tejler (el pr«*n*r* Tetter Tears a«s 1VS* Daps te maturity Fig. 2.-Regression of firsness values on the successive stages of maturation. Broken lines indicate the actual values. Unbroken lines indicate the values for the calculated regression line. 28 The lose in firmness between the corresponding successive stages of maturation differed in 1957 and 1958, although the trend was similar. In both years the initial small decrease in firmness accelerated rapidly with maturation. Comparison of the figures of lot a (fresh peaches) in 1957 and 1953 with the anticipated figures (proposed by Craft) shows that the firmness values actually obtained for each stage of maturation were very close to the anticipated figures. The pressure test standards represented in the table and those originally developed by Craft (12) are thus a good guide to determining the stage of maturation. Table A also presents data an peaches stored under conditions of lot b (room ripened peaches) and lot c (cold stared and room ripened peaches). These peaches had undergone excessive softening and were ripe when tested. B. Color Tests 1. Subjective Tests a. Test with the USDA Color Chart When harvested at the most inraature stage (7 days to maturity); the peaches had a green ground color with little or no red overlay. When harvested at the most mature stage (0 days to maturity); the fruits had a yellow ground color with considerable red overlay. Table 5 depicts the average color chart readings for both years as well as figures obtained with the regression equation. 29 TABI£ 5.-USDA Color Chart values of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1958 Average Color Chart Readings Year Lot A or Days to Maturity CR 7 6 5 4 3 2 1 0 1957 a A 3.1 3.6 3.7 3.6 3.8 3.8 -- 1957 a CR 3.6 3.6 3.6 3.6 3.6 3.6 - - 1958 a A 2.4 2.6 2.9 2.9 2.7 3.7 3.9 4.0 1958 a CR 3.1 2.1 3.1 3.1 3.2 3.2 3.2 3.2 1958 b A 3.4 3.8 3.8 3.9 4.0 4.0 4.0 - 1958 c A 3.9 4.0 4.0 4.0 4*0 4.0 4.0 - The table shows that the readings made with the aid of the color chart increased through the stages of maturation, indicating a decrease in green and an increase in yellow and red with maturation. Statistical analysis showed a significant linear regression over the whole period of maturation (Figure 3). Fig. 3.-Regressian of color values with the successive stages of maturation. Broken lines Indicate the actual values. Solid lines Indi cate the values for the best fitted line. Readings an 1 and 0 days to maturity In 1957 were not obtained. The linear regression curves were almost parallel, showing thereby a similar trend In the color change with maturation In both years. Howevert the absolute color value for each stage of maturation was different In each year. This variation was due to sample variation from year to year and different growth status of the trees. The peaches were greener in 1953 than In 1957, as is clear from the lower color values of the different stages of maturation in 1953. 31 Table 5 shows color readings for peaches stored under conditions of lot b (room ripened peaches). Since they did not show any signi ficant regression, the regression equation was not applied. However, the mean actual figures in lot b in 1958 showed a slight variation in color values from one stage to the next. Most stages had a slightly lower color value than the next more mature stage. This shows that less mature peaches with lower color values at harvest finished with lower color values after storage. The values of lot c (cold stored and room ripened peaches) in Table 5 show that most stages of maturation had no green color in the skin and there was no significant regression. Comparison of lot a (fresh peaches) and lot b (room ripened peaches) for 1958 shows that peaches after lot b storage had a cor respondingly higher color value for each stage of maturation. Com parison of lot a and lot c (cold stared aid room ripened peaches) for 1958 shows that the peaches in lot c had a correspondingly higher color value. Comparison of the figures on lot b (room ripened peaches) and lot c (cold stored and room ripened peaches) for the year 1958 shows a relatively greater loss of green color talcing place in lot c storage. Clearly the length of storage determined the amount of loss in green color. b. Test with Upehall’s Peaoh Chart Data for lot a (fresh poaches) in Table 6 shows that the peaches rose in cfclor values with maturation, indicating a decrease in green and an increase in yellow and red. 32 TABLE b.-Upshall^ Peach Chart values of Halehcven peaches at eight stages of maturation prior to harvest and after storage during 1957-1958 Average Color Chart Readings Year Lot A or Days to Maturity CR 7 6 5 4 3 2 1 0 1958 a A -- 1.1 1.4 1.5 2.3 2.9 3.0 1958 a CR - - 1.2 1.2 1.7 2.3 2.8 3.0 1958 b A 2.0 2.5 2.9 2.7 2.9 2.9 3.0 - 1958 b CR 2.1 2.4 2.7 2.9 3.0 3.0 2.9 - 1958 c A 2.9 3.0 3.0 3.0 3.0 3.0 3.0 3.0 33 Statistical analysis shoved a distinct cubic regression over the whole period of time (Figure 4)« U p .h11 . 1. hatk Cfc.rt Lot ( • ) T to r 19>0 /* U 1 *> 2 4u 2 &i' to * 1 * 3i >210 D iy t to Maturity Fig. 4-o-Hegressicn of color values in the successive stages of maturation. Broken lines indicate the actual values. Unbroken lines indicate the values for the calculated regression line. Table 6 shows the color change in lot b (room ripened peaches) in storage. Statistical analysis Indicated a significant regression over the whole period. The data showed a distinct rise In color values as maturity was approached with the exception of the 1 day stage. This relationship is well illustrated In Figure 5. 34 I r a M U ' i Fh i I Ck*rt *• tUtarltf Fig. 5•-Regression of color values In the successive stages of maturation. Broken lines indicate the actual values, in unbroken line indicates the values for the calculated regression line. Between the stages of 5 and 0 days to maturity the peaches rose in color value from 1.1 to 3.0. This rise was not uniform as is evi dent from the shape of the Sigmoid curve obtained, though the major por tion of the curve was linear, reflecting a uniform rise in color values. 35 Tho results show also that the amount of green that a peach had after lot b storage depended upon greenness before storage. These results were similar to those obtained with the USD! Color Chart. Most stages of lot c (cold stored and room ripened peaches) had no green color as Indicated by the 3.0 value presented In Table 6. Only one stage, 7 days, was not totally devoid of green color. Data In Table 6 shows that peaches after lot b (room ripened peaches) storage had a relatively higher color value than the cor responding stages of lot a (fresh peaches). The data also shows tbt the color values after lot c (cold stored and room ripened peaches) storage were proportionately higher than for lot a. Furthermore, the data shows that the figures after lot c storage attained higher values than after lot b storage. Hence the length of storage was an outstanding factor In the loss of green color. 2. Objective Tests with the Gardner-Hunter Color and Color Difference Meter Table 7 gives the actual "Rd," "a," "b," and *a/b" values as well as the resulting data from the calculated regression line for each stage of maturation. Far comparison the table Includes also results from the color charts corresponding to these stages of maturation. a H^lMfiJ'OO^J'MJ'O'Off'OOOOOOO 099909999999999999999 lo I I I I I I I HrlH<\l<\ltf\<\l(V<\J<\J<\J(\JrO<\jKNK\K\K\K\KNK\ u HlDr»tDflOC04lDONON IS ^ O' O 4 00 00 ON O' O 0 * 0 o o o o o o i! rC||CiK\K\K\*0t ir\ un «r\ i/\ in 4 ID 4 H 00 ID K\ H CO (VI ir\ co on HKN4-lSNti)V0INOOflO • ••••• ♦ • • • • • • • • • • • 0\CONipaN4tplA4(\iHpONCN>lA4KN<\JHQO^VOlA4KN(UHp e N<\JWWNNOI<\l<\l<\l<\JNHH<\JC\l<\J<\l C^19 ^4NIMMDU\4KMVHOMD»N4K\(\IHMOllN4inniHO I I s St St ON IN H 2 2 2 37 A graph showing the relationehip of scales "a* and ”b" to visual color is given in Figure 6. V -ao -is -10 -s o s io is 20 S a a \ a ►< / Or«iB onr m * v \ ai aI / | 9 Fig. 6,-Color diagram showing the relationship of "a" and "b" values to visual color. Lot a ■Rd" values Inspection of the "Rd" values (luminous reflectance values) far 1957 and 195 S in lot a (fresh peaches) shows that the most immature stage of maturation had the highest and the most mature stage the lowest "Rd" value. Between there was a continuous decline in "Rd" values. The results showed a significant regression in both years (Figure 7). 38 0*riR«r-Hut*r Color oa4 Color Difforonco iitor Lot (o) * M rolooo Yooro 1 9 ) 7 on* 1 9 5 i 1957 .4i 5 0 . 0 Lri.O 765%Jilo Deyr to Maturity Fig,7o-Regression of "Rd” values In the successive stages of maturation. Broken lines represent the actual values. Solid lines represent the values for the best fitted line. The results therefore shew that a characteristic of approaching maturity is a decline in "Rd" (luminous reflectance) values. Further more, the curves for 1957 and 1958 were almost parallel, reflecting similar differences in "Rd" values between stages of maturation. As might be expected, the absolute value for each stage of maturation was different in each year. "a" values An examination of "a" (green-red) values for 1957 and 1958 in lot a reveals that in both years the most imaature stage had the lowest and the most mature the highest "a" values. In between the "a" values showed a continuous rise. Statistical analysis of the data showed a significant regression in both years (Figure 8). 39 a,r,,*r-Duat,r Color u f Color Dlfroroaoo Motor ♦a'rolooo -0.J a* «• -i.8 - 7.8 7 6 5 k i I 1 o Dojro to Motor4tj Fig,8.-Regression of *a" values in the successive stages of maturation. Broken lines illustrate the actual value. Unbroken lines illustrate the values for the calculated regression line. One index of maturity is therefore a rise in "a* (green-red) values. The curve for 1957 and 1953 had similar slopes, reflecting similar differences in "a" values for each stage of maturation. Tet the corresponding absolute "a* values were not the same. Since in 1957 "a" (green-red) values rose frcm -8.7 to -2,9 frcm 7 to A dmya to maturity, green color continued to decrease until the U days to maturity stage. After this the "a" values developed a plus sign along uith a rise in values, indicating an increase in red. In 1958 between the 7 and 5 days to maturity stages the *att values rose from -5*8 to -0.05, indicating a decrease in green color. Further more, beyond this stage the values had a plus sign. This too shows that an increase in the red color took place as maturity was approached. "fr" v Examination of "b" (yellow-blue) values for 1957 and 1958 in lot a (fresh peaches) discloses a decrease with maturation. Statistical analysis Indicated a significant regression which is clearly demon strated in Figure 9. aardaar-lluatar Color Co Him. Lot (a) T**r. m 7 and lv>8 O Da/a to Maturity Fig. 9.-Regression of Nb" values in the successive stages of maturation. Broken lines indicate the actual values. Unbroken lines indicate the values for the calculated regression lines. a Again the curves far 1957 and 1958 are almost parallel. However, the absolute "b” (yellow-blue) values for the corresponding stages of maturation were not the same as can be seen in Figure 9 and Table 7. These data thus indicate that an index to maturity las a fall in the "b" (yellow-blue) values with approaching maturity. A positive sign throughout means that the skin remained in the range of yellow color throughout the eight stages of maturation. "ft/fe". xfllwe The values of ratio "a/b11 for 1957 and 1958 on lot a (fresh peaches) show that the most immature stage had the lowest "a/b" value, after which the "a/b" ratio increased to a peak value at the 0 days to maturity stage. Statistical analysis showed a marked regression (Figure 10). l.CW 1957 0.12 *•!« 1. Maturity Fig. 10,-Regression of "a/b* values in the successive stages of maturation. Broken lines illustrate the actual values. Solid lines illustrate the values for the best fitted line. 42 The shape of the curves vas different in both years* The 1957 data yielded a linear regression while in 1958 a curvilinear regression was found* The slopes of the two curves varied enough to show that the yearly differences in the "a/b" ratio between stages of maturation was not constant* The absolute values of the "a/b" ratio for the corresponding stages of maturation were not the same in 1957 and 1958* However, the general trend of the values of "a/b" was a continuous rise in the values of the "a/b" ratio* Lot b "Hd" values The values of "Rd" (luminous reflectance) in 1958 on lot b (roan ripened peaches) show a decline in "Rd" values with maturation with few exceptions* However, statistical analysis failed to show the existence of regression* "a" values The "a" values (green-red) for lot b in 1958 continued to increase with maturation* Statistical analysis showed a significant regression* These "a" values had a plus sign in the most inxnature stages indicating no green color developed during storage (Figure 11)* 43 Oordnor-Nuntor Color Color atfforonco 11.9 11.1 10. J 9.S (1.7 o * U1 i,. 6.J 'j.5 5 «t Day* to Fig* 11*-Regression of "a" values in the successive stages of maturation* Broken line represents the actual values* Unbroken line represents the values for the best fitted line* In the more mature stages the high values of Ma* continued to rise* Thus it is clear that the red color increased to maturity* "b" values The values on scale Nb* (yellow-red) in 1953 on lot b (roan ripened peaches) decreased with maturation* Statistical analysis shewed a significant regression illustrated in Figure 12* 'l*rdn*r«Hunttr Gtlvrh 4 Color Ttrnci «ot*r 36.7 Voluot 36.0 3}.J > 6.6 >W 11.1 > 1.6 > 1.1 '■>.6 1^*7 5 6 J i Day* to Matuntjr Fig. 12.-Regression of "b" values in the sucoessive stages of maturation. Broken line indicates the actual values. Unbroken line indicates the values far the calculated regression line. These values of scale Nb" (yellow-red) after lot b storage (room ripened peaches) were very close to the corresponding values of this scale in lot a (fresh peaches). No change had apparently taken place in the "b” values during lot b storage (Table 7). "a/b* values The 1958 "a/b11 values of lot b (room ripened peaches) show a rising trend, with a few exceptions, with maturation. However, statistical analysis failed to show a significant regression. 45 Lot c "Rd" values The 1958 "Rd* (luninoufl reflectance) values of lot c (cold stored and room ripened peaches) show a continued decrease with maturation* Statistical analysis showed a marked regression (Figure 13)* OorOoor-Huotor Color aa* Color HolHIDlfforoaoo Rotor 6 0 . 0 Lot (o) Toor 1VH 97.0 51.0 ? 6 9 J t 1 0 Ooja to Maturity Fig* 13.-Regression of "Rd" values on the successive stages of maturation* Broken line indicates the actual values* Solid line in dicates the values for the best fitted line* "a" values The 1958 "a" values (green^ed) of lot c (cold stored and room ripened peaches) show an upward trend with maturation* Statistical analysis indicated a significant regression (Figure 14)* 46 ~al»r )irftr*nc* 16.10 10. ib 9.10 7 6 5 ( 1 B»y» lo Maturity Fig* l4*-Regression of "a" values on the successive stages of maturation* Broken line represents the actual values. Unbroken line represents the values for the calculated regression line* "b" values In 1953 the "b” values (yellow-blue) of lot c (cold stored and room ripened peaches) showed a declining trend with maturation* Statistical analysis showed a significant regression (Figure 15)* 47 '1ir4nfr*i| 1/.75 1*.$0 7 6 & 4 } Day* to N a tjr. Fig* 15*-Regression of "b" values on the successive stages of maturation* Broken line Illustrates the actual values. Solid line Illustrates the values far the best fitted line* "a/b" values The values of the ratio "a/b" for 1958 of lot c (cold stored and room ripened peaches) shoved an Increase as the fruits matured* Statistical analysis disclosed the presence of a significant regression (Figure 16). 43 OarlHr*ltMl*r Calar H fttrix t Mat.r U t (•) 1.16 1W# 1.11 A I 0.66 t o.n i D i j i it Mltrlli Fig* 16.-Regression of "a/b" values on the successive stages of maturation. Broken line Indicates the actual values. Solid line Indicates values of the best fitted line. Comparisons between lots A decrease in "Rd" values (luninoua reflectance) took place in storage, since the relative values for lot b are lower than those for lot a. Lot c values were also comparatively lower than those far lot a. Yet a greater decrease in "Rd" values took place under conditions of lot b storage (room ripened peaches) than for lot c storage (cold stored and room ripened peaches) according to unexplained lever corresponding values for lot b. "A" values (green-red) In 1958 were higher for lot b (room ripened peaches) than for similar stages of lot a (fresh peaches), shewing an Increase of "a" values In storage. Similarly, the values for lot c (odd stored and room ripened peaches) were correspondingly higher than those for lot a. The values for lot c are oanparatively higher than those for lot b. Storage thus Increases the "a" values of peaches. 49 Comparison of "b" values (yellcw-blue) In 1958 for lots a and b shows no consistent Increase or decrease taking place during lot b storage* Yet, when the corresponding values for lots a and c are compared, the values of lot c are higher. 1 comparison of lots b and c Indicated again higher values for lot c* Thus lot c storage yielded a definite increase of "b" values which lot b did not* Examination of "a/b" values in 1958 far lots a and b showed relatively higher values for lot b* Comparison of the same values for lots a and c similarly indicated an Increase In "a/b" values in storage. In all stages but one the "a/b" values of lot c exceeded those of lot b, a further confirmation of the trend toward an Increase of "a/b" values in storage* Table 7 also Includes the average color chart readings (USD A Color Chart and Upshall’s Peach Chart) for the eight stages of matura tion* When the relative "a* values and "a/b" values are compared with the USDA Color Chart and Upshall's Peach Chart values, these four indioes showed agreement in every lot* The color values on these four Indices ascended as the peaches approached maturity* Co^Lar A color diagram was obtained when the "a" (green-red) and "b" (yellow-blue) values for the different stages of maturation were plotted* Figure 17 is the color diagram for lot a (fresh peaches) for 1957 and 1958, while Figure 18 presents lot b (roan ripened peaches) and lot c (cold stored and room ripened peaches) for 1958 only* 50 Color DU|n* Lot i T « i 1957 195** -20 -15 “1® "J ® J 10 U *> R a 9 o 9> Fig* 17.-£olor diagram of "a* and '’b** values* shewing the changes in color in the successive stages of maturation. ColorDiOff — Lot* b and c Tow 19V V -30 -15 -10 -5 0 5 10 1J 20 l o t < ti a l o t b 9 > ° a pj_g # 18*-Color diagram of “a** and *b** values shewing the changes in color in the successive stages of maturation. 51 Figure 17 shows the changes In color undergone by peaches with maturation In both years. A linear relationship was obtained with most points falling an the line. The curves for both years were almost paral lel and similar, Indicating that the changes In color among the different stages of maturation were about the same in both years. As might be ex pected, the absolute colors for each stage were different In both years. The yellow-green color changed to shades of orange as peaches approached maturity. Figure IS reveals the color changes undergone by the peaches under conditions of lot b (roan ripened peaches) and lot c (cold stared and room ripened peaches) in storage. A linear relationship was obtained for both lots with almost all points falling on the line. The curves for lot b and lot c showed both like and unlike characteristics. Both curves were in the same color sector (orange). Peaches of both lots had lost all green color after storage. Between the different stages of maturation the fruits of both lots showed a decrease in yellow color and a sharp gain in rod color. The unlike characteristics were the absolute color of each stage of maturation after lots b and c storage.and the groater increase in red color in the skin in lot c storage. C. Chemical Tests 1. Soluble Solids Percentages Table S includes the average soluble solids percentages for both years as well as the figures obtained from the calculated re gression line. 52 TABLE 8.-Refractanetric soluble solids percentages of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1958 Soluble Solids Percentage Year Lot A or Days to Jfeturity CR 7 6 5 4 3 2 1 0 1957 a A 12.3 12.4 10.7 11.5 11.9 10.9 12.2 12.9 1957 a CR 12.5 11.8 11.4 11.2 11.3 11.6 12.1 12.8 1958 a A 9.5 9.6 9.6 9.2 9.2 9.7 10.9 11.7 1953 a CR 10.0 9.5 9.2 9.2 9.5 10.0 10.7 11.6 1957 b A 12.6 11.4 11.5 12.9 11.2 11.S 11.6 - 1958 b A 10.2 11.5 10.6 10.8 10.4 10.5 10.5 - 1957 c A 12.4 12.7 12.1 12.6 12.5 11.9 12.9 13.5 1957 c CR 12.7 12.4 12.3 12.2 12.3 12.5 12.9 13.3 1953 c A 11.0 10.7 10.1 10.4 10.8 10.6 10.7 10.7 The regression figures presented on lot a (fresh peaches) shew the changes in the percentage of soluble solids undergone by the fruits with maturation. Statistical analysis of the data showed a significant regression In both years. An initial decline from 7 to 4 days to matur ity was followed by an increase In the remaining stages of maturation. Thus Figure 19 shows two maximum^ a lesser one at 7 days to maturity and a greater maximum at 0 days to maturityj the minimum is located at the stage of 4 days to maturity (Figure 19)* 53 lalakU ItLlii Lot <■) H.gToor 1957 •■< 195* U. u.o 11.6 * 11.1 t i t 10.8 i d •*• 3 10. 9.8 ? 6 5 J » 1 0 Day* ta Haturltj Figa 19a-Regression of soluble solids percentages on the successive stages of maturation. Broken lines represent the actual values. Solid lines represent the values for the calculated regression line. The results shew that an Initial decrease of soluble solids per centage preceded an Increase with maturation. The curvilinear regres sion curves In both years were almost parallel with a similar slope throughout. Differences In the percentage of soluble solids between the suooessive stages of maturation were thus similar In 1957 and 1953. (See Figure 19). However, the absolute percentage of soluble solids for each stage of maturation was different in each year. For example, the percentage of soluble solids at 7 days to maturity in 1957 was 12.5 as compared to 10.0 in 1958. Obviously this resulted from yearly sample variation. 54 Table 3 embodies the reeulta of lot b (roan ripened peaches) storage in 1957 and 1958. As the results shoved no significant re gression, no trend In the percentage of soluble solids in this lot can be described* The regression figures on lot c (cold stared and roan ripened peaches) in 1957 disclose a decreasing trend at first and then a rise with maturation. Statistical analysis shaved the existence of a weak but definite regression. Between 7 and 3 days to maturity the per centage of soluble solids decreased, while in lot a (fresh peaches) the percentage decreased for a shorter period between 7 and 4 days to matur ity (Figure 19). In lot a the percentage of soluble solids rose after 4 days to maturity but In lot c after 3 days to maturity. As In lot a, the results of lot c also shoved the presence of two marl mums in the percentage of soluble solids, a lesser maximum at 7 days and a greater one at 0 days to maturity (Figure 20). 55 13.* n.<» 13.2 13.0 U.l •■ 12.6 9 12.* a 12.2 *4 3 12.0 iv,n 5 * 3 2 »*y* t* Maturity Fig* 20.-Regression of soluble solids peroentsge on the successive stages of maturation* Broken line represents the actual figures* Solid line represents the values for the best fitted line* The data presented for lot c for 1958 show that almost the same results were obtained as in 1957* But the statistical analysis failed to show any regression* Comparison of lots a and b far 1957 shews that most stages had a higher soluble solids percentage after lot b storage* But in 1958 all stages except 1 day had a higher percentage than the corresponding stages In lot a* Thus at least the results of 1958 strongly suggest that the peaches underwent an increase In the percentage of soluble solids in lot b storage* 56 Comparison of lots a and c shews that peaches had a higher per centage of soluble solids after lot c storage , the only exception being 0 days in 1958. Thus the results provide strong evidence that the peaches increased in the percentage of soluble solids in lot c storage* Comparison of lots b and c reveals that four stages in 195 S and all stages In 1957 shewed a higher soluble solids percentage after lot c storage* Thus at least the results of 1957 indicate that a greater increase in the percentage of soluble solids occurred in lot c storage* This is due to longer storage in lot c* 2. tfydrogen Ion Concentration (pH) The results of this test are illustrated in Table 9* 57 TJLBLE 9.-PH values of Halehaven peaches at eight atages of maturation prior to harvest and after storage during 1957-1958• Hydrogen Ion Concentration (pH) Year Lot A or Days to Ma1iurity CR 7 6 5 4 3 2 1 0 1957 a A 3.9 3.9 3.6 3.6 3.7 3.8 3.7 3.9 1957 a CR 3.9 3.8 3.7 3.6 3.6 3.7 3.8 3.9 1958 a A 3.6 3.2 3.3 3.2 3.2 3.5 3.7 3.8 1958 a CR 3.5 3.3 3.2 3.2 3.3 3.4 3.6 3.9 1957 b A 3.6 3.6 3.6 3.7 3.7 3.8 3.8 - 1957 b CR 3.5 3.6 3.6 3.7 3.7 3.7 3.8 - 1958 b A 3.3 3.4 3.5 3.5 3.7 3.7 3.8 - 1957 c A 3.7 3.7 3.8 3.8 3.8 3.9 3.9 4.0 1957 c CR 3.6 3.7 3.7 3.8 3.8 3.9 3.9 4.0 1958 c A 3.7 3.7 3.7 3.7 3.7 3.8 3.8 3.9 1958 c CR 3.7 3.7 3.7 3.7 3.7 3.7 3.7 3.7 The regression figures of lot a (fresh peaches) show the changes In pH undergone by the peaches with maturation. Statistical analysis showed a strong regression in both years (Figure 21). t7«r*r»» 1m C«Hn 5.7 i i «•e Hl \J.J Ki f 5 u*7i t« Maturity Fig* 21.-Regression of pH valu»s on the successive stages of maturation. Broken lines indicate the actual values. Unbroken lines indicate the values for the calculated regression line. A decrease fran 7 to 4 days to maturity preceded an increase in pH for the remaining stages. The lesser and greater mail mums in the pH values in each curve were not the same in 1957 as in 1956. Thus it appears from the results of both years that there was a definite trend of an Initial decrease fallowed try an increase in pH toward maturity. The curvilinear regression curves were parallel throughout their length (except near 0 days to maturity). Thus differences in the pH values between the successive stages of maturation were about the same in 1957 and 1956. However, the absolute pH value for each stage of maturation was different each year, due to sample variation (Table 9 and Figure 21). 59 The regression figures on lot b (roan ripened peaches) far 1957 reveal a alight continuous rise In pH from one stage to the next. This regression was significant statistically (Figure 22). 5,B0 M (b) T « r 1*57 3.77 , 5 j.m ms. D«7« te ntnrilj Fig. 22.-Regression of pH values m the successive stages of maturation. Broken line represents the actual values. Unbroken line represents the values for the calculated regression line. Figures cn lot b in 1953 shot a similar slight definite upward trend in pH, but statistical analysis failed to show any regression of significance. Perhaps the best inference is that there was a definite increase In pH but that the regression test was not refined suffici ently to discover this trend. An Inspection of the regression figures on lot c (cold stored and roan ripened peaches) discloses an upward trend In pH with maturation. Statistical analysis showed the existence of a signifi cant regression In both years. The regression curves, which were both linear, had different slopes (Figure 23). 60 fc.OO ftftrtg**L*t (a) Ih Come Taara 1VS7 •»* 19H 0 f 1J.M Oaja la m i i n t f Fig* 23,-Regression of pH values on the successive stages of maturation* Broken lines indicate the actual values* Solid lines indicate values for the best fitted line* Comparison of lots a and b for 1953 shows that with the ex ception of 7 days to maturity, peaches increased in pH values in lot b (room ripened peaches) storage. In 1957 an increase in the pH values after lot b storage was shown by the last four stages only* But the trend for both years seems to be a rise in pH in lot b storage* Comparison of lots a (fresh peaches) and c (cold stored and room ripened peaches) for 1957 shows that with the exception of 7 and 6 days to maturity, peaches Increased in pH after lot o storage over the corresponding stages for lot a* In 1958, except for 0 days, all stages showed an increase in pH after lot c storage* 61 Comparison of the figures on lots b (room ripened peaches) and c (cold stared and room ripened peaches) shows that corresponding pH values were higher after lot c storage, with the exception of 0 days in 1958. Thus *11 comparisons indicate that pH increases with storage. 3, Titratabie Acidity Percentage The results of both years are given in Table 10. TABUS 10.-Titratabie acidity percentages of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1958. Titratabie Acidity Percentage Year Lot A Days to Maturity or CR 7 6 5 4 3 2 1 0 1957 a A 0.91 0.97 0.74 0.70 0.80 0.64 0.60 0.50 1957 a CR 0.93 0.83 0.82 0.76 0.70 0.64 0.59 0.53 1958 a A 0.87 0.90 0.85 0.80 0.74 0.70 0.70 0.60 1958 a CR 0.91 0.87 0.83 0.79 0.75 0,71 0.67 0.63 1957 b A 0.96 0.80 0.80 0.68 0.70 0.59 0.53 - 1957 b CR 0.92 0.85 0.79 0.72 0.66 0.59 0.53 - 1958 b A 0.94 0.82 0*79 0.79 0.75 0.72 0.63 - 1958 b CR 0.90 0.86 0.82 0.78 0.73 0.69 0.65 - 1957 c A 0.78 0.75 0.59 0.52 0.65 0.54 0.51 0.32 1957 c CR 0.76 0.71 0.66 0.61 0.56 0.50 0.45 0.40 1958 c A 0.79 0.68 0.65 0.69 0.68 0.64 0.64 0.52 1958 c CR 0.75 0.73 0.70 0.67 0.65 0.62 0.60 0.57 62 Table 10 presents the actual changes in the titratabie acidity as well as the figures obtained far the calculated regression line* Data far lot a (fresh peaches) in 1957 and 1958 Indicated a strong regression upon statistical analysis* There was a reduction In titratabie acidity with maturation with the most Immature stage having the highest and the most mature the lowest percentage of titratabie acidity* Figure 24 shows that between these two stages there was a fall in the percentage of titratabie acids in both years* Lot (*5 * T**r* 1V57 and 1958 VO SO 4 70 1957 S t c 50 *•!» t* Mlwltr Fig* 24*-Regression of titratabie acidity on the successive stages of maturation* Broken lines Indicate the actual values* Solid lines indicate the values for the best fitted line* However, the absolute values for titratabie acidity for each matura tion stage were different in each year* The fact that the slope of the curve in 1957 was different from that for 1958 indicates that the differences in the percentage between successive stages were unequal in both years* Furthermore, the stages 7 and 6 days to ma turity were higher in titratabie acidity in 1957 than in 1953, but the other stages were lever in 1957* The results of lot b (roan ripened peaches ) storage an titra tabie acidity percentage indicate a decline with maturation in both years* Statistical analysis showed a significant regression from the highest percentage in the first stage to the lowest in the last stage (Figure 25), .97 Tltr*t«b)» Acidity Lot (b) T*arc X'iVf *nd 19>fl 7 • 3 * 3 « 1 Day* to ibttrlty Fig* 25*-Hegression of titratabie acidity on the successive stages of maturation* Broken lines indicate the actual values* Solid lines indicate the values far the calculated regression lines* The slope of the curve of 1957 differed fraa that of 1953, re vealing variations in the percentage of titratabie acids between 64 stagos which differed each year* The two curves cross between 7 and 6 days to maturity. At 7 days the percentage of titratabie acidity was higher in 1957, but the other stages were then lower than in 195£. The curves of lot b are very similar to those of lot a In the over all position and In the crossing point. The results of lot c (cold stared and room ripened peaches) show that the titratabie acidity percentage decreased with maturation. Statistical analysis showed a marked regression (Figure 26). .80 Tltr.t.bl. A.idity Lot (*) .75 T.ara 1957 but 1958 .70 .60 •a u b I .55 « 3 b 3 i I 0 8 . / . to U t M i t ; Fig. 2$,-Regression of titratabie acidity on the successive stages of maturation. Broken lines represent the actual values. Un broken lines represent the values far the calculated regression line 65 The least nature stage at harvest had the highest percentage of titratabie acidity while the most mature had the lowest* The curves for 1957 and 1956 had different slopesf Indicating yearly differences in the percentage of titratabie acidity between stages. These curves also cross each other between 7 and 6 days to maturity* At 7 days to maturity the percentage of titratabie acidity was higher In 1957, but the other stages were lower* The two curves were very similar to the curves far lots b and a in their position and crossing point* Al though the total titratabie acidity decreased with maturation In both years, the corresponding absolute figures reflect a yearly variation after lot c storage. Comparisons of lots a (fresh peaches) and b (room ripened peaches) disclose that peaches decreased in the relative percentage of titratabie acids after lot b storage. A comparison of lots a and c (cold stored and room ripened peaches) shows a relatively lower percentage of titratabie acidity after lot c storage* A comparison between lots b and c reveals lower titratabie acidity for each stage after lot c storage* A decrease in the percentage of titratabie acidity with Increasing storage is thus evident* 4* Index Number Test The values of this Index can be calculated fran the values of pH and the percentage of titratabie acids* The index numbers, calculated for each stage of maturation in each lot in both years, are given in Table 11* 66 TABLE 11.-Index numbers of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1956. Index Number t 10 '.7 Year Lot A Days to Maturity or CR 7 6 5 4 3 2 1 0 1957 a A 9.2 8.7 22.6 23.9 13.8 13.6 22.2 17.0 1957 a CR 11.8 13.3 15.3 17.8 19.7 21.7 23.7 25.7 195 S a A 28.7 52.4 39.5 59.0 56.8 20.3 28.7 19.8 1953 a CR 32.8 4 % 5 49.7 51.6 49.1 42.2 30.9 15.3 1957 b A 19.7 21.0 23.5 22.1 21.3 18.1 22.4 - 1953 b A 35.6 32.5 26.8 26.7 20.0 20.0 16.9 - 1953 b CR 34.9 31.8 28.6 25.5 22.3 19.2 16.1 - 1957 c A 19.2 17.7 20.2 22.8 18.2 15.7 16.5 21.1 1953 c A 19.1 22.2 23.0 21.8 19.8 18.7 16.7 16.3 1953 c CR 20.3 21.2 21.6 21.4 20.7 19.4 17.6 15.2 Table 11 gives the actual figures as veil as the figures obtained frcm the calculated regression line. Statistical analysis of the figures on lot a (fresh peaches) showed a significant regression in both years (Figure 27). 67 r»d*» DiMtr Lot (•> T#,r, 1 9 V •nd I9 5 8 39 IO +tm X ■ 1957 5 * 3 1 to Maturity Fig* 27,-Regression of index numbers on the successive stages of maturation. Broken lines indicate the actual values. Solid lines indicate the values of the best fitted line. In 1953 the index numbers at first rose and then fell with maturation. In 1957* however* the peaches shewed a rise in index numbers with maturation. These results at variance are seen in the graphs far 1957 and 1953 in Figure 27, The curves are different in slope as well as shape* and the absolute values of index numbers far eaoh stage were also different. The writer has not been able to ascertain any ex planation for this variance in the behavior of index number values. The results of lot b (room ripened peaches) storage on the index number values are represented in Table 11 and Figure 28, 63 )*> >o iS So 26 + I * ► h 22 10 18 16 D . j . to Uttrttf Fig. 28.-Regression of index numbers on the successive stages of maturation. Broken line indicates the actual values. Unbroken line Indicates the values for the best fitted line. Statistical analysis shoved no regression in 1957* although the index numbers rose from 7 days to 5 days and then declined. Perhaps the best hypothesis is that there is ah initial rise in index number values followed by a fall after the 5 days stage, but that the regression test is not sufficiently refined to discover it. In 1958, however, the index number values of lot b (room ripened peaches) showed a continuous decline towards maturity.and statistical analysis showed a distinct regression (Figure 28). The most immature stage had the highest index number value, while the most mature stage had the lowest. Again the results of both years are at variance. 69 Table 11 also depicts the results of lot c storage (cold stared and room ripened peaches)* In 1957 the values of index numbers rose to a peak at A days and declined afterwards with maturation* Two inconsistencies were the values of 1 and 0 days to maturity, which were higher than their preceding stages* Although the statistical analysis failed to show any regression, there may be a trend which the regression test is not refined enough to detect. In 1958 the index number values of lot c (cold stared and room ripened peaches) showed a significant regression upon statistical analysis (Figure 29)* lad** Nua»*r Lot (*) T * * r 19^4 15 7 « 5 * > * 1 0 Fig* 29*-Regression of index numbers an the successive stages of maturation* Broken line indicates the actual vaJoes* Unbroken line indicates the values of the calculated regression line* 70 A trend of Index number values rising to a mmtimal value followed by a decline toward maturity was noticed. This was similar to the 1958 trend observed for lot a (fresh peaches)* In general the results of lot c (cold stored and roan ripened peaches) were similar in 1957 and 1958, although they showed a significant regression In 1958 only. The yearly absolute values on Index number after lot c storage for each stage were about the same. These small yearly variations were much smaller than similar variations In lots a and b. In 1957 index number values after lot b storage (roan ripened peaches) were correspondingly higher than far lot a (fresh peaches) with the exception of the A days and 2 days to maturity stages. This shows that peaches underwent an increase in Index number values in storage. Yet in 1958 stages other than 7 days had a lower Index number value after lot b storage than the corresponding stages of lot a. The results of 1957 and 1953 are thus antagonistic. There fore, it Is difficult to tell whether index number values increased or decreased in storage under conditions of lot b. Comparison of lots a (fresh peaches) and c (cold stored and roan ripened peaches) in 1957 shows that with the exception of 2 and 1 days to maturity stages, all stages had a higher relative index number value after lot c storage. However, in 1958, most stages show lower values after lot c storage, with the exception of 2 and 1 days to maturity. The results of 1957 and 1953 are thus antagonistic. There fore, no trend toward Increase or decrease in index number values during lot c storage can be described. Peaches of each stage had a lower Index number value after lot c (cold stared and room ripened peaches) storage than after lot b (room ripened peaches) storage with the exceptions of the A day stage in 1957 and 2 and 1 days to maturity in 1958. Thus In both years far the corresponding stages of maturation, the index number values were lower after lot c than after lot b storage. 5. Soluble Solids/Adds Ratio The values of this index were calculated from the values of soluble solids and acids far each stage of maturation in each lot and In both years. The results are given in Table 12. 72 TABLE 12.-Soluble solids/acids ratios of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1958. Soluble Solids/Acids Ratio Year Lot A Days to Maturity or CR 7 6 5 4 3 2 1 0 1957 a A 13.5 12.8 U . 5 16.5 U . 9 17.0 20.4 17.0 1957 a CR 13.0 13.8 U .6 15.4 16.2 17.0 17.9 18.9 1958 a A u . o 10.9 11.3 11.5 12.4 13.8 15.6 19.4 1958 a CR 11.3 10.8 10.8 11.4 12.5 u . i 16.2 18.9 1957 b A 12.7 U . 2 U . 3 18.6 15.9 19.9 21.8 - 1957 b CR 12.4 13.9 15.3 16.8 18.2 19.7 21.1 - 1958 b A 10.9 u . o 13.5 13.7 13.9 U .6 16.6 - 1953 b CR 11.9 12.5 13.2 13.9 U . 5 15.2 15.9 - 1957 c A 15.9 17.0 20.5 24.2 19.3 22.0 25.3 42.2 1957 c CR 13.9 16.6 19.3 22.0 24.6 27.3 30.0 32.7 1958 c A 13.9 15.8 15.6 15.2 16.0 16.6 16.8 20.6 1958 c CR u . o U .6 15.3 16.0 16.6 17.3 18.0 18.6 The table gives the actual figures on soluble solids/acids ratio as well as the figures obtained from the regression equation. Statistical analysis of lot a (fresh peaches) values indicated a strong regression in both years. However, whereas a linear regression was obtained in 1957, a curvilinear regression was traced in the 1958 data (Figure 30). 73 Lot (o) 19.9 Tooro 1997 ... 199* 18.5 4 9 9 5 10 , Dajro to Mtiiritr Fig# 30.-Regression of soluble solids/acids ratios on the successive stages of maturation. Broken lines Indicate the actual valuesoSolid lines indicate the values for the best fitted line. In 1957 the soluble solids/acids ratio showed a continuous rise with maturation. In 195H the ratio showed a decrease in value between 7 and 6 days to maturity, after which it rose tcvard maturity. However, it may be noted that the major portion of the soluble solids/acids curve far 195& possesses a linear shape like that of 1957. Thus the results of both years suggest that the soluble solids/ acids ratio of peaches rose as they progressed toward maturity. How ever, the absolute values on soluble solids/acids ratio for each stage were different in 1957 and 195&. Also the slopes of the curves dif fered, revealing annual differences in the soluble solids/acids ratio between the adjacent stages of maturation. Since the curve for 1958 occupies a lower position, the soluble solids/acids ratio for each stage of maturation was lower in 1958. This yearly variation was due to sample variation. Statistical analysis of lot b (room ripened peaches) data revealed a strong linear regression in both years.(Figure 31). f 6 5 * y i Day. to Maturity Fig. 31.-Regression of soluble solids/adds ratio on the succes sive stages of maturation. Broken lines represent the actual values. Unbroken lines represent the values for the calculated regression line. The figures illustrate a rise in the soluble solids/acids ratio with maturation. The curve for 1957 was steeper than that for 1958, which indicates that the rise in soluble solids/acids ratio between successive stages of maturation was greater in 1957. The absolute figures of solu ble solids/acids ratio on each stage was also different in each year. 75 Statistical analysis of lot c (cold stored and roan ripened peaches) data determined a strong linear regression in both years (Figure 32), Rati tat {•> Taara 1 « 7 *a4 !<#>« Daya to Nitarltr Fig, 32,-Regression of soluble solids/acids ratio on the successive stages of maturation. Broken lines indicate the actual values. Unbroken lines indicate the values far the calculated regression line. The results reveal an increase in the soluble solids/adds ratios with maturation. The slopes of the curves and the absolute ratio for each stage were different in 1957 and 1958* Since the curve far 1958 occupies a lower position on the graph, the soluble solids/adds ratio was relatively lower in 1958, 76 A comparison of the soluble solids/acids ratio of lots a (fresh peaches) and b (roam ripened peaches) shows relatively higher ratios after lot b storage except for 7 days to maturity in 1957 and 1 day to maturity in 1953. A comparison of the soluble solids/acids ratio of lots a and c (cold stored and room ripened peaches) indicates clearly that the ratio for each stage of maturation was higher after lot c storage. Comparison of lots b and c reveals conclusively that the soluble solids/acids ratio for each stage of maturation was higher after lot c storage. When the results of the three lots are taken together, it becomes apparent that the soluble solids/acids ratio increased with storage. 6 . Chlorophyll Content Test The chlorophyll content of each stage of maturation in each lot of peaches for each year is Indicated in Table 13. 77 TABLE 13.-Chlorophyll contents of Halehaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1958 Chlorophyll Content (mg./lOO g. of tissue) Year Lot A A. Days to hkturity or CR 7 6 5 4 3 2 1 0 1957 a 6.00 4.23 6.64 4.45 6.88 2.94 1.85 3.15 1958 a 1.85 1.58 1.20 1.00 1.32 0.05 0.00 0.00 1957 b 0.13 0.55 0.04 2.29 3.15 9.94 0.13 - 1958 b 0.12 0.06 0.00 0.00 0.00 0.00 0.00 - 1957 c 3.80 7.10 7.55 1.20 1.20 5.50 6.42 6.22 1958 c 0.00 0.01 0. 0 0 0.0 0 0.00 0.00 0.00 0.00 B. Groups of Stages of Maturation Group 1 Group 2 Group 3 Group 4 1957 A 5.12 5.55 4.9 1 2. 5 0 1957 CR 5.09 5.66 4 . 8 0 2.53 1958 A 1.72 1.10 0.68 0.00 1958 CR 1.71 1.15 0.60 0.04 1957 A 0.34 1.17 6.54 0.13 1958 A 0.09 0.00 0.00 0.00 1957 A 5.45 4 . 3 7 3.35 6.32 1958 A 0.00 0.00 0.00 0.00 With maturation chlorophyll content alternately rose and fell. The results were quite erratic. Consequently, no trend in the varia tion of chlorophyll content during maturation is clear. The irregu larity and inconsistency in the results was due to sample variation within the peaches and from peach to peach of the same stage of maturation. This sample variation was apparently larger than the true chlorophyll variation from one stage of maturation to the next. Since it is very difficult to be sure that the peaches have been picked exactly one day apart, it was decided to group pairs of days to see whether peaches of two days apart in maturation showed any trend in chlorophyll content. Consequently, 7 and 6 days, 5 and 4- days, 3 and 2 days, 1 and 0 days to maturity stages were arranged into four groups. The figures of each group were averaged. The results of these four successive groups of stages of maturation in each lot were compared. Table 13 contains the figures on chlorophyll content for « each stage of maturation as well as figures for the four groups of stages of maturation in the three lots. Results far lot a (fresh peaches) in Table 13 demonstrate the changes in the amount of chlorophyll in the successive groups of stages of maturation. Statistical analysis shewed a significant regression in both years (Figure 33). 79 6 n C M i n t Lot (a) 1957 J.O 1.2 Dajra to Maturity Fig* 33*-Regression of chlorophyll content an the successive stages of maturation* Broken lines Illustrate the actual values* Solid lines Illustrate the values far the best fitted line* In 1958 the most imnature group had the highest amount of chloro phyll and the most mature group the lowest, with a continuous decline In chlorophyll values between these two points* But In 1957 the chloro phyll content increased between group 1 and group 2 and thereafter moved downward till maturity* The figures of lot b (room ripened peaches) In Table 13 fail to show any continuous rise or decline In the amount of chlorophyll with maturation* Statistical analysis failed to show any regression* In 1958 the amount of chlorophyll was small and became aero after group 1* In 1957 the amount of chlorophyll increased between groups 1 and 3 and BO then declined* The chlorophyll content of each group after lot b storage did not seem to depend on the initial amount of chlorophyll* The results of lot c (cold stored and room ripened peaches) in Table 13 fall to show any continuous rise or decline in the amount of chlorophyll with maturation* Statistical analysis failed to discover any regression* In 1958 the amount of chlorophyll was very small and became zero after group 1* In 1957 the amount of chlorophyll decreased between groups 1 and 3 and then rose* Comparison of the figures on lot a (fresh peaches) and lot b (room ripened peaches) shows that peaches decreased in the chlorophyll content after lot b storage* However, in 1957 the chlorophyll content of group 3 of lot b was higher than that of the corresponding group in lot a* Comparison of the chlorophyll content of peaches in lots a (fresh peaches) and c (cold stored and room ripened peaches) shows that the figures of lot c are lcwer, except that the chlorophyll content of group A- in lot c in 1957 is lower than in lot a* Comparison of chlorophyll content in lots b (room ripened peaches) and c (cold stored and room ripened peaches) in 1957 shows lower figures for lot b (Table 13)* In 1958 the chlorophyll content in both lots was very low; most of the time it was zero* Thus no comparison could be conducted between lots b and c in this year* But the results of 1957 show a greater decrease in the amount of chlorophyll in lot b storage* The results of the three lots considered together reveal that chlorophyll content was lcwer after storage, but the decline was relatively greater after lot b storage than after lot c storage* 7* Carotene Content Test The carotene content of each stage of maturation in each lot is recorded in Table 14* 82 TABLE 14.-Carotene contents of Halebaven peaches at eight stages of maturation prior to harvest and after storage during 1957-1958 Carotene Content (mg./lOO g« of tissue) Year Lot A A • Bays to Maturity or CR 7 6 5 4 3 2 1 0 1957 a A 0.10 0.07 0.42 0.51 0.36 0.09 0.49 0.38 1958 a A 0.39 0.52 0.59 0.56 0.60 0.36 0.60 0.47 1957 b A 0.04 0.27 0.58 0.42 0.20 0.38 0.29 - 1958 b A 0.22 0.45 0.32 0.51 0.29 0.48 0.45 - 1957 c A 0.26 0.33 0.33 0.17 0.34 0.15 0.41 0.23 1958 c A 0.27 0.32 0.48 0.51 0.61 0.51 0.77 0.84 B. Groups of Stagfee of Maturation Group 1 Group 2 Group 3 Group 4 1957 a A 0.06 0.43 0.22 0.44 1958 a A 0.4.5 0.58 0.48 0.54 1957 b A 0.15 0.50 0.29 0.29 1958 b A 0.34 0.41 0.39 0.45 1957 c A 0.30 0.25 0.25 0.32 1957 c CR 0.28 0.28 0.28 0.28 1958 c A 0.30 0.50 0.56 0.81 1958 c CR 0 .30 0.46 0.62 0.78 Since carotene content increased and decreased between stages, the relationship of carotene to the stage of maturation is not clear. Tliis inconsistency was due to sample variation within the peaches and from peach to peach. This sample variation was larger than the true variation for several reasons. First, it is very difficult to pick peaches exactly one day apart. Secondly, the method of taking slices from peaches is subjective, since the analyser selects what he considers the greenest part. Thirdly, the slices were obtained from places of varying carotene content on the peach. Thus variations in samples can make a study of the changes lnthe carotene content between stages of maturation difficult. To overcase the difficulty of picking peaches exactly one day apart it was decided to divide the eight stages into four groups to see whether peaches two days apart reveal any trend in carotene con tent. Consequently, figures far 7 and 6 days, 5 and 4 days, 3 and 2 days, 1 and 0 days to maturity stages were averaged. The results of these four successive groups of stages far each lot, as shown in Table 14, were studied. The figures for the four groups on lot a (fresh peaches) indicate that an increase in the amount of carotene took place from one group to the next, although statistical analysis failed to shew any regression. In both years the most mature group had the highest amount of carotene and the most immature group the lowest. Two erratic points were grow* 2 (5 and 4 days to maturity stages) in both years, whioh had more carotene than group 3. Perhaps the 24 best hypothesis would be that a trend of an increase in carotene with maturation exists which the regression test is not sufficiently refined to detect* Figures on lot b (roan ripened peaches) in Table 14 show a rise in carotene with maturation. The most inmature group had the lowest amount while the most mature group had the highest. In each year, however, group 2 had a higher carotene content than group 3. Statis tical analysis showed a weak regression for 1952 only. The figures on lot c (cold stared and roan ripened peaches) in Table 14 show that in 1957 a decrease in the carotene content in the first two groups was followed by a rise toward maturity. In 1952, how ever, an upward trend in carotene content toward maturity is evident. The statistical analysis showed a significant curvilinear regression in 1957 and a linear regression in 195B (Figure 34). o5 .86 Carolaaa Coattit .78 Lot (c) Taara 1957 aa* 1958 .70 .82 «• s* 0 m » >4 o1 “m •<*8 >0 ft « ar • 28 6.5 V 5 2.5 0.5 Daya to Maturity Figa 34#-Regression of carotene content on the successive stages of maturation# Broken lines indicate the actual values# Solid lines indicate the values for the best fitted line# Comparisons of the figures on lot a (fresh peaches), lot b (room ripened peaches) and lot c (cold stared and room ripened peaches) shou no trend toward increase or decrease in carotene due to differen tial storage conditions# 86 V* Discussion of Results This research involved studying changes in peaches during a period frcm 7 to 0 days to maturity and the evaluation of various indices far distinguishing stages of maturation of Halehaven peaches. Physical and chemical tests were made on Halehaven peaches in 1957 and 1958* Samples of each stage of maturation were divided into three lots: lot a* which was analysed immediately, and lots b and c, which were analysed after storage. A. Maturation Phasei Lot a (Fresh Peaches) 1. Physical Indices The results with lot a Indicate the changes undergone by peaches during the maturation phase. A continuous decrease in the firmness of peaches toward maturity was revealed by the results with the Durcmeter, as shown in Table 3. For example, the Durometer reading of 96.9 at 7 days declined to 83.1 at 0 days to maturity. Since there is no report in the literature on the use of the Durosieter to determine stages of fruit maturation, this, therefore, is presumably the first study of its use far this purpose. The advantages of the Durosieter are its speed, simplicity, portability, and the fact that it does not render the specimen unsalable. Che difficulty is the flat base of the instrument, which does not fit the curved surface of the peach, causing variations in readings according to the angle of the Instrument against the peach. A redesigned instrument would be mare accurate. £7 The moisture and turgidity of the peaches at the time of testing Influences firmness readings; nitrogen levels may play a part in firmness. The Influence of weather upon firmness is seen vhenf for example, a few days of warm sunny weather may result in hard ripe peaches becoming so soft that they cannot be shipped even short dis tances. There were yearly variations due to sample variation. Yet the firmness readings obtained with the Durometer far stages of matura tion studied herein can be of considerable value to discern the stages of maturation of peaches. Mmmeaa-Tavlor Pressure Tester Haller and Harding (22), Morris (29)# and Coe (6) proposed that pressure tests could be uaed to indicate the stages of maturation of peaches, but they did not reccnmend pressure test ranges far these stages. In this study pressure test ranges were determined far stages of maturation one day apart. Peaches showed a decrease in the resistance to the hkgneea- Taylar pressure tester as maturity was approaohed, as the firmness standards given in Table 1 .indicate. For example, from a pressure of 15*5 to 16.0 at 7 days a peach declined in pressure at 0 days to ma turity to approximately 0.6 pounds. Thus, by testing with the Magness- Taylor pressure tester and by comparing its firmness readings against the standards, it can be determined what stage of maturation a peach has attained (days to maturity). The yearly variation with the hhgnesa-Taylor pressure tester resulting frcm sample variation was very small. The firmness values obtained in this study also approximated the anticipated figures suggested by Craft (12) far each stage of maturation* However, the instrument, by puncturing the fruit, renders it unsalable* The speed at which pressure is applied can change results up to 0*5 pounds* Moisture, turgidity, nitrogen levels and weather may also influence Magnese-Taylar firmness readings, yet it seems that the resistance to the plunger of the Magness-Taylor pressure tester is a dependable Index of the stage of maturation. USDl Color Chert and tlnehallU Peach Chert In Tables 5 and 6 may be seen the color standards with the USDA Color Chart and Upshall's Peach Chart for each stage of maturation* Both charts showed an Increase in color readings toward maturity, in dicating a loss in green and an Increase in yellow color* Since yearly differences in absolute color values far each stage and the growth status of the tree make it impossible to seleot a given color value for a stage of maturation, and, since peaches of a given color vary each year in softness, color standards must be calculated with given maturation stages for each season* Although both charts yielded sub jective data, Upshall's Peach Chart, rendering wider intervals between stages, seemed to be slightly superior far detecting stages of matura tion two days apart* All color charts are dependent upon the ability of the worker to discern fine color values to tenths of points between shades* During maturation there was also an increase In red color, al though neither of these color charts measures the change in red oolor, 89 which was quite noticeable and la undoubtedly of importance in marketing peaches. Qardner-Hunter Color and Color Difference Mater Three scales of the automatic Qardner-Hunter Color and Color Difference Mater were usable as indices of maturation* ”RdN (luminous reflectance), "a" (green-red), and "b" (yellow-blue). A ratio of the scales "a" and "h" ("a/b") end a color diagram (Fig. 17) constructed from the values of "a" and ”bN were found to be good indices of stages of maturation. The standards obtained with the four factors, which are given in Table 7, reveal yearly variation in the absolute values far each stage, due to sample variation. With maturation the values on scales ”Rd” and "b* declined while the values on scale "a* and ratio ”a/bN in creased. Although "Rd," "a,* "b,” or "a/b* could be used as an index to the stages of maturation, the ratio Na/bN appeared superior, since the two scales cover changes in green, yellow, red, and blue, and its range of values is nearly as wide as that of the other three factors. After the standards for these objective indices of color have been determined, as in Table 7, a peach can be read in the instrument and referred to the standards. The color diagram in Figure 17 indicates the visual color of the peaches of each stage in a manner superior to the USDA Color Chart and Upshall's Peach Chart. It illustrates changes in red as well as green and yellow. The color diagram is usable for reliable and reproducible determination of stages of maturation. Its prepara tion, however, is time-oonstadng. 90 In describing the superiority of objective color indices, Des- rosier (16) pointed out that subjective color evaluation varies fran Inspector to Inspector, day to day, and season to season* Whipple (35), delimiting the human eye In color determination, declared that illumina tion varied daily and hourly* Using the Qardner-Hunter Color and Color Difference Mater, Francis (19) obtained accurate and reliable results with the skin color of apples* Thus, although limitations arise due to variable growth status of the tree, weather, locality and sample varia tion, objective ground color indices can be excellent guides to stages of maturation for peaches as well* Exact standards, however, may have to be established and corrected by scientific tests* 2* Chemical Indices Although general studies have been made previously of the behavior of certain chemical Indices during maturation, no attempt has been made to classify the successive stages of maturation of peaches by using such Indices as tltratable acidity percentage, concentration of hydrogen ions, percentage of soluble solids, index number, soluble solids/acids ratio, chlorophyll content and carotene content* These chemical Indices have been Investigated herein and the standards for daily stages of maturation have been constructed* Soluble Solids Percentage Although the percentage of soluble solids In both years first decreased and then increased, as shown in Table 8, the yearly absolute percentage for each stage differed, due to probable yearly sample variation* The practicality of using soluble solids percentage as 91 an Index Is limited by the curvilinear relationehip of the Index with maturation. In initial decrease in soluble solids percentage followed by a rise thus revealed a soluble solids percentage of about 9.95 for 7 and 2 days and 9*23 for 5 and 4 days to maturity in 1953. Dimorphic behavior of the values also occurred in 1957 data as shown in Table 8. In addition! differences in the percentage of soluble solids between the successive stages are often less than 0.5 percent, too far accurate differentiation. Fisher and Britton (17), Fisher, Britton, and O'Reilley (13), and O'Reilley (31) found that the range between mature and ijnature fruit was too narrow. Allmendinger et al. (2) observed that soluble solids increased about 30 percent with Elberta and about 22 percent with J. H. Hale peaches between "shipping" and "canning" stages. Simpson (33) reported the percentage of soluble solids to show a gradual rise throughout the season. Willlaan (37) observed that the tendency far the percentage of soluble solids in peach juice to In crease during the period before and after maturity is neither definite nor consistent enough to be of value. The feasibility of using soluble solids percentage as an index to stages of maturation therefore seems questionable. Hydrogen Ion Concentration in initial decline in pH was fallowed by a rise with maturation according to the standards in Table 10. This curvilinear regression makes the feasibility of pH standards as an index to the stages of maturation doubtful. Probably yearly sample variations caused pH 92 values for the corresponding stages to differ in 1957 and 1958* Since pH values vere dimorphic and the differences in pH values between stages were too (in most oases less than 0.2), the same reasons that invalidate the use of soluble solids percentage disqualify hydrogen ion concentration as an index. The highly buffered system of the peach makes pH not sensitive enough for the evaluation of stages of maturation. Titratable Acidity Percentage A decrease in the percentage of titratable ad d s occurred with saturation at harvest, as shown in Table 10. Each stage of maturation rendered different percentages of titratable acidity in 1957 and 1958, due probably to yearly sample variation. The differences in the per centage of titratable acidity between stages were fairly large. The results of this study agree with those of Blake and David son (6), Culpepper and Caldwell (14), and Neubert (30), who pointed out that the titratable acidity of peaches decreased with maturation. Allen (1) noted that the percentage of a d d s in peaches usually varied between 0.5 and 1.0 percent, a range which occurred in this study as well. The percentage of titratable acidity seems to be a promising index to the stages of maturation of peaches. The test was objective, the results were consistent, and the values of the successive stages of maturation could be separated. The only handi cap was that the test specimen had to be pressed far juice. 93 Tndaar Mumhar The study of index number as related to stages of maturation, as shown in Table U , resulted In contradictory results. In 1957 the index number values portrayed an upward trend with maturation, while in 1958 the values increased in the first four stages and declined in the last four. Ccmin and Sullivan (11), and Blake and Davidson (6) have hypothesized that index number may control complex equilibria within fruit and that it represents the balance between the accumulative and destructive tendencies in fruit. Although they inferred that the size of the index number is related in some way to the physiological condi tion of the fruit, they did not reccnmend index number as a criterion far stages of maturation. Although, as a derived index, this objective test is easy to compute, the present results do not warrant its use. Soluble Solids/Acids Ratio The soluble solids/adds ratio showed an increase between stages during maturation, as shown in Table 12. Leonard (26) found that the value of the soluble solids/acids ratio increased from 16 to 36 during maturation of Halford peaohes, while Rsyneke's (32) range from 13.8 to 19.9 compared more closely to the ranges of 13.0 to 18.9 in 1958 of this study. Consistent, objective and reliable results and large differences in the values of adjacent stages make the soluble solids/acids ratio a promising index to peach maturation. Therefore, this is one of the better indices to the stages of maturation. Slaoe the values of this 94. Index may be derived from other indices, it does not have to involve a test specimen* ChlgroatorUi gflrtwrt The characteristic feature of this index was a decline in chlorophyll content with time, as Table 13 shows* The results agree with the observation of Kramer ft^* (25), who found by spectro- photanetric and fluarcmetrlc methods that delay in harvesting caused a reduction in green pigment* The estimated decrease in chlorophyll content between groups was too slight to afford an adequate index of daily stages of maturation, although it may be possible to detect stages two to three days apart* This laboratory test is time-consuming, requiring care in sampling, extraction, and repeated washings, while the method of talcing slices from the peach Is subjective* Differences in the amount of chlorophyll within a peach and from peach to peach may be larger than the true chlorophyll content variation between stages* This test, therefore, does not seem to hold much premise* Carotene Content The characteristic feature of this Index seems to be an Increase in carotene content with time, as shown in Table 14. The results sug gest that an increase in the amount of carotene possibly took place between groups (stages of maturation groups), although statistical analysis failed to show any significant regression* The regression test may not be sufficiently refined to detect this trend* The carotene content index is time-consuming, requiring a pro longed prooedure and considerable precaution In sampling. 95 extracting, filtering, refluxing, and washing. The method of ob taining slices from peaches is subjective, since variations in the carotene content at different places on the same peach and on different peaches may be larger than the true variations between stages. These variations can be large enough to make the results inconsistent and erratic. Although this index may differentiate stages of maturation threo or mare days apart, the use of carotene content as an index to daily stages of maturation is very unsatisfactory. B. Storage and Ripening Phasesi Lots b (Room Ripened Peaches) and c (Cold Stored and Room Ripened Peaches) 1. Physical Indices Durometer and Mamess-Taylor Pressure Tester Since the peaches in these phases had undergone softening and were ripe when tested, no significant regression was found with the Durometer and Magness-Taylar pressure testers. The room ripened peaches of lot b tested about 1 to 2 pounds with the Magness-Taylor instrument and about 70.0 with the Durometer, regardless of the readings at harvest. The cold stored and room ripened peaches of lot c also tested about the same after storage with the Magness- Taylor and Durometer testers, Irrespective of the readings at harvest. Color Tests TISDA Color Chert and ITnahal^la Paeah Tables 5 and 6 show that both the USDA Color Chart and Upshall's Peach Chart registered a decrease in green and an increase in yellow color after storage. Sine® lot o was kept at 4Z° F. for 9 days 96 initially before being ripened at 70° F., longer storage was probably responsible for a greater loss of green color than for lot b, which o was ripened at 70 F. There was also a noticeable increase in red color during storage, though neither of these charts measures this change, which is undoubtedly of value in marketing peaches* Gardner-Hunter Color and Color Difference Meter The downward trend in the values of scales nRdB and "b1* and an increase in "a" and "a/h" values was less apparent after lot b storage (room ripened peaches) than after lot c storage (cold stared and room ripened peaches), due to the longer storage period of the latter. 2. fflinml rAl ladlfififi Soluble Solids Percentage A greater upward trend in the percentage of soluble solids occurred after lot c storage (cold stared and room ripened peaches), since lot b storage (roam ripened peaches) was shorter* However, this Increase was false, since the two opposing forces of loss of water due to transpiration and loss of sugars due to respiration influenced the changes in soluble solids percentage* Transpiration tends to increase the percentage of soluble solids, while respiration tends to diminish it* According to Allen (l) and Culpepper and Caldwell (14), any gain in the percentage of soluble solids in storage is due to loss of water, Similarly, Harding and Harding (22) stated that sugars in storage tend to Increase or decrease depending an the relative ratio of transpiration and respiration* 97 Hydrogen Ion Concentration ifydrogen ion concentration in storage declined with maturation as is clear from the rising pH values toward maturity in lot b (room ripened peaches) and lot c (cold stored and room ripened peaches). In fresh peaches hydrogen ion concentration had increased and then decreased with maturation. That an Increase in pH values occurred in storage is evident from the higher corresponding values for each lot over the preceding one stored far a lesser period. Similarly, Neubert et al. (30) reported an increase in the pH value of peaches during storage after picking. Titratable acidity Percentage Peaches decreased in titratable acidity percentage in storage, as is shown by correspondingly lower titratable acidity percentage values for the stored lots than for the fresh peaches of lot a. The greater decrease in titratable acidity percentage of lot c than of lot b resulted from longer storage of the former. Davidson (6), Culpepper and Caldwell (14.), and Neubert £&, al. (30) reported a decrease in the titratable acidity percentage of peaches ripened after picking. luflssf. HHBhwr For the room ripened peaches of lot b in 1957 and for the cold stored and room ripened peaches of lot c in both years the index number values showed a rise in the first three or four stages followed by a decline with maturation. The 1958 values for lot b descended through n~i 1 stages, as shown in Table 11. 93 As compared to the values for the fresh peaches of lot a* the index number values for lots b and c were relatively higher in 1957 and lower in 1953. These yearly antagonisms make it difficult to analyse the behavior of index number values In storage. Soluble Solids/Acids Katio A rise in the soluble solids/acids ratio in the successive stages was seen in lot b (room ripened peaches) and lot c (cold stored and room ripened peaches) in both years. Less mature peaches with lower initial soluble solids/acids ratios finished with lower ratios after storage. That an Increase in the soluble sollds/aclds ratio occurred in storage is evident from the higher corresponding values for each lot over the preceding one stored far a lesser period, Chlorophyjj. Cqp.tept Lower chlorophyll content values of room ripened peaches in lot b and the cold stared and room ripened peaches of lot c than the corres ponding 1957 values for fresh peaches indicated a decrease in chloro phyll content in storage. As Table 13 shows, this decrease was greater for lot b than for lot c peaches, although lot c storage was longer. For this illogical observation the writer has not been able to discover any explanation. Carotene Content For the room ripened peaches of lot b an increase in the amount of carotene possibly took place between groups, although statistical analysis failed to show any significant regression. The regression test may not be refined enough to detect this trend. See Table 99 For the cold stored and room ripened peaches of lot c in 1957 there was a decrease in the carotene content followed by a rise toward maturity, while in 1953 the carotene content showed an upward trend towards maturity. Comparison of lots a, b and c failed to reveal any comparative trend toward a change in the amount of carotene due to lot b or lot c storage, C. Correlations ££& Magness-Taylcr ftrqgytfM? Tester with Other Indices (Based on lot a Values) The liagness-Taylor pressure tester, widely used by investi gators to study peach maturity indices, was used in this study as a guide to the collection of samples. It rendered the minimum varia tion in yearly readings for corresponding stages of maturation. Hence, correlations of the firmness readings with the Magness-Taylar pressure tester with other physical and chemical indices were determined, A correction for yearly variation made the computed correlation on a "within-year11 basis. 100 Carrelatittia of the Mumaaii-Tavlor Pressure Teeter with other Indican Index r df Degree of Significance USDA Color Chart -0.869 12 «* Upehall's Peach Chart -0.956 4 ** Duraneter 0.946 12 Gardner-Hunter "a/b* -0.933 12 #* Soluble solids percentage o .s a 14 * PH 0.445 14 N.S. Titratable acidity percentage 0.902 14 ## Soluble solids/acids ratio -0.685 14 *« Index number 0.242 14 N.S ** - Significant at 1% * - Significant at 5% D. 2U12H Correlations The indices which seem to be correlated positively or negatively are listed below in groups. 1. la&ssa with Descending Linear Regression Curves The following indices possessing descending linear re gression curves could be positively correlated to each other. a. Duraneter firmness values b. Gardner-Hunter "Rd" values c. Gardner-Hunter "b** values d. f>fegneas-Taylor firmness values e. Titratable acidity percentage f. Chlorophyll content (in 1958 only) 2. Indices with Ascending Linear Regression Curves The following indices possessing ascending linear regression curves could be positively correlated to each other. a* USDA Color Chart b, Upehall* s Peach Chart c, Gardner-Hunter "a" values d, Gardner-Hunter "a/bn values e, Index number (In 1957 only) f, Soluble solids/acids ratio (in 1957 only) 3. Indices with an Initial Followed by & Rise The following Indices possessing curvilinear regression curves, showing an Initial fall followed by a continuous ascent toward maturity, seem to be positively correlated to each other* a* Soluble solids percentage b* Ifydrogen ion concentration c. Soluble solids/acids ratio (in 1958 only) 4* Indices with aik Initial Rise Followed by & The following indices possessing curvilinear regression curves, showing an initial rise followed by a fall until maturity, seem to be positively correlated to each other* a* Chlorophyll content (in 1957 only) b* Index number (in 1958 crQy) 5. Negative The following negative correlations seem to existt a* The indices of the first and second groups seem to be negatively correlated with each other* b* The indices of the third and fourth groups seem to be negatively correlated with each other* 102 £• Suggested Indices Based 31 Lot a Data The writer believes that certain characteristics, when considered as the ratio of one to the other can act as indices to the stages of maturation of peaches* 1. Ratios of Color and Firmness In this study peaches showed with the progress of maturation a decrease in firmness values both by the hfegneas-Taylor pressure tester and the Durometer, while they indicated an increase in color values by the USDA Color Chart, Upshall1 a Peach Chart, and "a* and "a/b" values by the Gardner-Hunter Color and Color Difference Mater. The ratios of the firmness factors to the color factors are probably accurately representative of stages of maturation. The values of these ratios continue to decrease as maturity approaches. a. Firmness values by Ifegness-Taylar pressure tester Color values by USDA Color Chart b. Firmness values by Magness-Tavlor pressure tester Color values by Upshall*s Peach Chart c. Firmness values by Ifegness-Taylor pressure tester Color values from Gardner-Hunter Ha/brt values d. Firmness values by Mamesa-Tavlor pressure tester Color values from Gardner-Hunter "a" values e. Firmness values by Durometer Color values by USDA Color Chart f. fjjawgg vfllwe by tmrqrcta Color values by Upshall* s Peach Chart g. Firmness values by Duraneter Color values from Gardner-Hunter •‘a/h" values h. Firmness values by Durometer Color values fran Gardner-Hunter Ha* values 103 Similarly, a reciprocal of the above ratios can be used as an index to the stages of maturation of peaches. The values of these reciprocals continue to increase toward maturity. Tho reciprocals can be calculated fran the ratios presented above and since both the ratios as well as their reciprocals are merely index numbers, the scale on which they are presented is of little value. 2* Rftttog gqlqar iosl Acidity According to this study the percentage of titratable acidity decreased with maturation while the color values by same indices increased. The ratios of the titratable acidity percentages to these color values are probably accurately indicative of stages of matura tion. The value of these ratios decreased as maturity was approached. a. Titratable acidity percentage Color values by USDA Color Chart b. Titratable acidity percentage Color values by Upshall* s Peach Chart c. Titratable acidity percentage Color values by Gardner-Hunter "a/b" values d. Titratable acidity percentage Color values by Gardner-Hunter "a" values A reciprocal of the above ratios could be used as an index to the stages of maturation of peaches too. The values of these recipro cals increased toward maturity. The above discussion indicates that certain indices have definite value in differentiating stages of maturation. No index was fully satisfactory since peach fruits change physically and chemically at a slow daily rate which is greater under conditions 104 of higher temperatures. Consequently seasonal variations in the absolute values of these indices with respect to a given stage of maturation occur due to fluctuating temperatures. Since no single index was infallible, the use of two or more indices might be valuable to ascertain maturation with greater accuracy. Indices made up of the ratios of pressure tester values to color chart values and Gardner-Hunter *a/b* and "a" values should be investigated along with the ratios of titratable acidity per centages to color chart values and Gardner-Hunter "a/b* and '•a* values. The possibility of the reciprocals of these ratios as indices to maturation should also be explored. 105 VI* Sunmary and Conclusions The most important findings of this study may be stated briefly i 1« In the maturation and storage phases the color values using the USDA color Chart and Upshall*s Peach Chart, Gardner-Hunter "a1* and "a/b" values, soluble solids/acids ratio, and carotene shewed an upward trend as maturity approached, A downward trend with the pro gress of maturation was evident in the values of titratable acidity percentage, resistance to the Duraneter and the l-fagnes3-Taylor pres sure tester, Gardner-Hunter nRdn and "b" values, and chlorophyll con tent, Soluble solids percentage and pH in the maturation phase showod a decrease in the first three or four stages followed by a rise till maturity. In the storage phase both the soluble solids and pH incroased in value,Carotene content in the maturation phase seemed to increase in the successive stages harvested, but in storage it neither increased nor docreased. The behavior of index number was unexplainable both during the maturation and ripening (storage) phases, 2, Changes in the values of these indices were greater under conditions of lot c (cold stored and roan ripened peaches) than under conditions of lot b (room ripened peaches) due to a longer period of storage of the fanner (with the exception of chlorophyll content). The following indices were found to be a reliable guide to the stages of maturation of peachest a. Firmness values with the Durometer b. Firmness values with the Magneas-Taylar pressure tester 106 c. Soluble solids/acida ratio d* Titratable acidity percentage e. Gardner-Hunter "a" values f. Gardner-Hunter "a/b" values g* Gardner-IIunter "Rd" values h, Gardner-Hunter *b" values 1. Gardner-Hunter color diagram The use of Upshall's Peach Chart and the USDA Color Chart was fair in the estimation of stages of maturation* Of these the former was superior* 5* Soluble solids percentage, hydrogen ion concentration, chloro phyll content, carotene content and index number were found to be inadequate* It is questionable whether any of these indices could be a useful tool in Indicating the stages of maturation* 6* Several indices made up of the ratios of color and firmness values or titratable acidity percentage and color values would be useful indices to the stages of maturation of peaches* 107 LITERATURE CITED 1. Allen, F. W. Physical and Chemical Changes in the Ripening of Decidous Fruits. Hilgardia 6: 381-/)/.1. 1932. 2. Allmendinger, D. F.# Overley, F. L* and Overholder, E. 0. The Relation of Harvest Ffaturity to Size and Weight of Peach Fruits. Washington Agr. Exp. Sta. Mini*. Cir. 8, 4 pp. 1943. 3. Association of Official Agricultural Chemists. Official Ifethods of Analysis. 1945. 4. Bedford, C. L., and Robertson, W. F. Harvesting and Ripening Freestone Peaches for Processing. Quarterly Bull. Mich. Agri. Exp. Sta. 37: 439-91. 1955. 5. Blake, M. A., Davidson, 0. W., Addams, R. M», and Nightingale, G. T. Development and Ripening of Peaches as Correlated with Physical Characteristics, Chemical Composition and Histological Structures of the Fruit Flesh: Physical Measurements of Growth and Flesh Texture in Relation to the Jtarket and Edible Qualities of the Fruit. N. J. Agr. Exp. Sta. Bui 525, 35 pp. 1931. 6. Blake, M.A. and Davidson, 0. W. Some Studies of the Degree of Maturity of Peaches at Harvest in Relation to Flesh Firmness, Keeping Quality and Edible Texture. N. J. Agr. Exp. Sta. Bid.. 606. 35 pp. 1936. 7. Cardinell, H. A. and Guinn, Barr C. Packing-house Treatments of Michigan Peaches. Reprinted from Michigan Agricultural Experiment Station Quarterly Bulletin 32: 70-93. 1949. 8. Coe, F. M. Peach Harvesting Studies. Utah Agr. Exp. Sta. Bui. 241 1933. 9. Comin, Donald Successful Storage of Peaches Depends on Maturity and Post-ripening. Ohio Farm and Home Research 40* #295. 1955 10. Comin, Donald and Sullivan, D. T. The Degree of Dissociation of Acids in the Rome Beauty Apple and its Relation to Number of Days fran Full Bloom. Proc. Amer. Soc. Hort. Sci. 62* 299-303, 1953. U . Comin, Donald and Sullivan, D. T. The Degree of Dissociation of Acids in the Rome Beauty Apple and its Relation to Maturation, Season, and Differential Nitrogen Levels. Proc. Amer. Soc. Hort. Sci. 63* 205-210. 1954. 12. Craft, C. C. Maturity Indices for Eastern-grown Peaches Based an Pressure-test Readings. 1955 National Peach Council Annual, Cairo, Illinois. 13. Croce, F. M. La Cosecha de Durasnos (Harvesting Peaches) Revlsta Mensual B.A.P., 1933, 16*193*17-22. 14* Culpepper, C. W. and Caldwell, J. S. The Canning Quality of Certain Cocmercially Important Eastern Peaches. Technical Bulletin No. 196, United States Department of Agriculture, Washington, 1930. 15. Davies, R., Bcyes, W. W. and De Villiers, D. J. R. Storage of Peaches. Rep. Low. Temp. Res. Sta. lab., Capetown, for the Year June 1936-June 1937. 1939. 16. De8rosier, N.W. Color Measurements with Tomatoes. From Color in Foods • • • • A Symposium. National Academy of Sciences— National Research Council, Washington, 1954. 109 17. Fisher, D* V. and Brotton, J. E. 1'hturity and Storage Studies with Peaches* Sci* Agr* 21s 1-17* 194.0* 13. Fisher, D* V., Britton, J. E., and 0*Reilly, H* J* Peach Harvest ing and Storage Investigations* Sci* Agr* 24i 1-16* 194% 19* Francis, F* J* A Mathod of Measuring the Skin Color of Apples* Proc* Amer. Soc* Hort. Sci. 60: 213-220, 1952* 20. Haller, M. H* Fruit Pressure Testers and Their Practical Appli cations* U* S* Dept* Agr* Circ* 627* 22 pp. 1941* 21. Haller, M* H. Handling, Transportation, Storage and Marketing of Peaches* United States Department of Agriculture. Bibliographical Bulletin No, 21. 1952. 22. Haller, M* H. and Harding, P. L* Effect of Storage Temperatures on Peaches. U. S. Dept* Agr, Tech* Bui* 630, 32 pp. 1939* 23. Hartman, E* II, and Cravens M* E,, Jr. Factors Affecting Retail Peach Sales* Reprinted fran Michigan Agricultural Experiment Sta tion Quarterly Bulletin, Vol. 32. 1949* 24* Havls, Lean Si al- Peach Growing East of the Rocky Mountains. Farmers* Bulletin No* 2021, U* S. Department of Agriculture* 195J* 25. Kramer, Amihud and Haut, I* C. Ripeness and Color Studies with Raw and Canned Peaches, Proc* Amer* Soc* Hort* Sci* 51(219-224, 1943* 26* Leonard, Sermon, Bar Shiun Luh, and Elly Hinrelner* Flavor Evaluation of Canned Cling Peaches* Food Technology 7:480-435.1953 27* Lott, R* V* The Terminology of Fruit Maturation and Ripening* Amer* Soc* Hart* Sci* Proc, 46t 166-172* 1945* 110 23. Mat sum at o, Kumaichi. Studios on the Physiological Changes in Peaches during Handling and Railroad Shipnent. Memoirs of the College of Agriculture, Kyoto Imperial University. No. 46 . Japan. 1939. 29. Morris, 0. M. Peach Maturity at Harvest as Related to Quality Wash. Agr. Exp. Sta. Bui, 266, 35 pp. 1932. 30. Neubert, A. M., Shulta, J. H., Bedford, C» L., and Carter, G. H. Processing Washington-grown Freestone Peaches. Wash. Agr. Exp. Sta. Institute of Agricultural Sciences, The State College of Washington, Pullman, Washington. Station Circular No. 63. 1948. 31. O’Reilly, H. J. Peach Storage in Modified Atmosphere• Proc. Amer. Soc. Hort. Sci. 49: 100-106. 1947. 32. Reyneke, John. The Final Ripening Period in Relation to Wooliness of Peregrine Poaches. Union of South Africa. Department of Agri culture and Forestry. Science Bulletin No. 228. 1941* 33. Simpson, Margaret. Fruit Maturity Indices. Horticultural Experi ment Station and Products Laboratory, Vineland Station, Ontario, Canada. Report for 1951 and 1952. 34. Upshall, W. II. and J. R. von Haarlem. Quantity and Quality of 4 Fruit (Fresh and Processed)— As Affected by Stage of hbturity at Picking Time. Ontario Horticultural Experiment Station, Vineland Station. Report far 1943 and 1944. 35. Whipple, S. R. Color Inspection— California Department of Agri culture. From Color in Foods— A Symposium. National Acadoay of Sciences. National Research Council, Washington. 1954* Ill 36. Willisan, R. S. Studies in Maturity and Cold Storage of Poaches. Sci. Agr. 21* 624-645. 1941* 37. Willison, R. S. Problems Relating to the Maturity, Transportation, and Storage of Peaches. Publ. Dotn. Lab. Plant Path. St. Catherines, Ontario. 4 PP. Undated. * 1 0 2 AUTOBIOGRAPHY I, Surinder Singh Attri, was born in Bassi, Fftnjab, India, on December 4, 1930. I received ny secondary school education at Sanatan Dharam Sanskrit English High School, Patiala, Panjab, India. After I received ny Intermediate Degree from Panjab University, I received a diploma in Forestry from the Indian Forest Ranger College in Dehra Dun. While employed as a forest ranger, I received the degree of Bachelor of Arts frcn Ptnjab University in 1954« I came to the United States in 1955, vhere, after a semester at Fresno State College in California, I transferred to Kansas State College. I was a research assistant for part of the tine beforo I recoivod tho dogroe of llaster of Science in Horticulture in 1957. I hold a position as research assistant at the Ohio State Univorsity vliilo completing the requirements for the degree of Doctor of Philosophy.