(Nutritive Value of Canned Foods)
EFFECT OF TIME AND TEMPERATURE OF STORAGE ON VITAMIN CONTENT OF COMbSERCIALLY CANNED FRUITS AND FRUIT JUICES (STORED 12 MONTHS)' DOROTHY S. RIOSCHETTE, WISIFRED F. HISMA4S, AND EVELYN G. HALLID.4Y The C'nizersity of Chicago, Chicago 37, I l l .
T h e effect of 4, 8, and 12 months' storage at SO", 65', and 80' F. o n the ascorbic acid, carotene, niacin, riboflaiin, and thiamine content of seventeen lots of canned fruits and fruit juices has been studied. Comparisons were also made as to the effect of a year's storage, in nine warehouses located in cities throughout the United States, on the ascorbic acid and thiamine content of tomatoes and orange juice. The canned foods, held under constant temperature conditions, at 50" F. show-ed no significant losses in ascorbic acid, thiamine, or carotene. Tomatoes showed a significant loss in niacin after 8 months of storage regardless of the temperature employed. In general,
storage at 63" F. also resulted in good retention of the Fitamins studied. The fruit and fruit juices stored at 80" F. showed definite losses in ascorbic acid and thiamine after 8 months, t$ hich increased with 12-month storage at this temperature. The retention of ascorbic acid a'nd thiamine in canned foods stored for 12 months in nine warehouses in different localities decreased as the :earl) aterage temperature increased. The retentions of ascorbic acid Faried from 7870 at hew Orleans aierape teniperature 77' F. to 100% in Uei+ l o r k aterape temperatnre 58' F. The retentions of thiamine iaried from Ric/, at Tampa aierage temperature ;io F. to 9;"' in Ye\+ York.
A
ciatioil-Can Mnnufacturcrs Institute Sutrition Rc niittee three constant tcmperatui toragc chainhers we're constructed at the laboratory for use in this csperiment. Teniperature records were kept on these chambers using the wadings of two th[>rnionieters in each, one placed abovc the caiincd foods, tht. o1ht.r at a low 1 The warehouses uscd ior storage of the other gi'oup of cspt~rimentalsaniplcs ere located i n S e w Orleans, La., Tampa, Fla., Tempe, - i r k . , T u b a City and Oakland, Calif., Washington, I>. C., St. Louis, N o . , Rochellc, Ill., and S e \ v Tork, S . l-, In these n-arehouses daily masiinum and niinirnum temperatures were recorded. The saniplcs for the earlier, more limited experiment ~ e r stored e in a refrigerator, a room-temperature storeroom, and an incubator, with average teniperatures maintained a t approsinlately 45 ', 70 ', and 08" F., respectively. TNE. I n addition to the initial analyses on the sanlples for controlled-temperature storage, assays for the five vitamins were made after I-, 8-, and 12-month storage intervals, arid one additional assay for ascorhic acid \vas made after the first 2- t o 4-week storage. For the warehouse-stored samples, assays for tn-o vitamins, ascorbic acid and thiamin, were made only after 12 months. For the preliminary csperirnent with grapefruit juice held a t 45 ', 70", arid 08" F., ascorbic acid assays were made a t intervals of 0.5, 4, 8, 12, and 18 months. C.ISSF;DFOOIJS.The can& food products stored a t constant temperatures anti analyzed at intervals were: three lots of grapefruit juice, one each from California, Florida, and Texas; one lot of Florida grapefruit segments; two lots of orange juice, one each from California arid Florida; t\yo lots of halvrd peaches, one clingstone and one frcestonc variety, both w-c~F;tcrn-gron.n;two lots of Hawaiian pineapple juice; one lot of Hawaiian zliced pineappltx; three lots of tomato juice, oiie each from canncrie8 in the eastern, {vestern, and midwestern production areas; and three lots of \\-hole tomatoes, one each from the same areas. The n-arehouse-stored samplrs included one lot of California orange juice and two lots of n-ePtern \\.hole tomatoes. T h r samples used in the preliminary study w're two lots of Texas grapefruit juice. All samples ivere of fancy or extra standard quality. The lots of cans for this storagc study \wre obtained during a period when each cannery was opvrating on a uniform lot of raw stork in t h e
SUMBER of studies on the nutritiw value of eanncd fruits
and vegetables have been reported in the last feiv years. The results point out t h a t canned foods are important sou the essential food nutrients. Since, hovf r , the unstable character of several of the vitamins suggests the possibility of apprceiable losses during storage, definite ini'ormati,nn is needed as to the effect of time and temperature o n these nutrients. =\ f ( v studies of limited scope on.the effrct of such variables in .torag(> conditions on vitamin retention in commercially canned foods have been published. These data shoiv t h a t both tinw and temperature affect the retention of ascorbic acid ( 7 , 15, 22, 26) and that temperature has a limited effrct on carotene retcntion but a marked effect, on thiamine (?). To widen the scope of informatioil o n this subjwt a mure estensive investigation was planned of the effect of t h e and temperature of storage on the retention of ascorbic acid, carotcne, niacin, riboflavin, and thiamine in commercially canned fruit and vegetable products. This paper presents the results obtained from the first, year's storage and esamination of certain of the more acid-pH below 4.5-fruit products. It includes the data obtained by periodic assays for t,he vitamins mentioned on seventeen lots of canned foods stored at three constant temperaturcs, as well as 1-year assays on three foods st,ored in nine xarehouses Located in areas having varied climatic conditions. I n addition, periodic assays are reported of a prclimiiiar>-experiment on the ascorbic acid in two grapefruit juice samples stored at thrcc other constant temperatures for 18 nionths:. EXPERIMENTAL COSDITIOYS
TEMPERATURES. The t,hrer constant temperatures chosen for the main project n-ere SO",65"> and 80" F. These temperatures were considered to cover the range of yearly averag? tempc'ratures of warehouses located in varied ai'eas throughout th? I-riited States. Moreover, the lowest temperature, 50 ' F., \\'as bclieved to offer a possibility of practical attainnicxnt from the standpoint of economy if results should indicate that cooler storage is !Tarranted. Through the cooperation of the Sational Caiincrs .isso1 This is the twenty-second of a series of ~ i a p e r sdealing with the general siihjcct "Sutritive Value of Canned Foods."
994
August
1947
935
INDUSTRIAL AND ENGINEERING CHEMISTRY
Figure 1. Effect of Storage Time on Ascorbic Acid i n Toniato, Pineapple, and Peach Samples SO3 F . -_-_-_ F. - - - - - - - 6jZ 80' F.
regular course of commercial production of retail-sized cans. In general the cans in each lot irere numbered consecutively i i i order of filling and closing, and were processed in one retort a t the saiiie time. There were I44 cans in the lots of samples u m l for controlled-temperature storage and 360 in ihoae used for controlletl-temperature storage a n d warehouse storage. Imniediatcly alter cooling they were cased and shipped. hipped t o the laboratory v e r e promptly assorted; i s cans ~r-ei'c.used for the initial assays, and the others n-ere placctl in storage under esperiniental conditions. T h e assortnient x i > made according t o the planned schedule in reference to call numbers; sis cans were allon-ed for each storage period and teniperature. These groups were arranged in such a tray t h a t no ont' assay would be made on a composite sample of cans coming froin the canning line in close sequence. I n this n-ay it n-as hoped that representative sampling for each treatment would be ensured as nearly as possible. Those cans to be stored in warehouses in thc different cities were sent directly there, and, after approsimatelj, 1 year, one or tn-o &can samples of each food were \vithdrann from storage a t each viarehouse and sent t o the laboratory for the scheduled assays. ASSAYS, S o t all five vitamins were determined for each of thc foods. T h e retention of ascorbic acid was followed for all seventeen samples, and t h a t of thiamine for all escept the grapefruit segments and freestone peach. T h e carotene and niacin contents were determined for peaches, tomatoes, and tomato juice, and riboflavin for tomatoes and toniato juice only. PREP.~RATIOX OF ShhfPLES. T h e procedure of preparing samples for withdrawal of the aliquots used for assays was the same as t h a t described by Hinman, Higgins, and Halliday (9). For niacin and riboflavin assays the aliquots n-ere taken from the 6ame type of blended mixtures as were those prepared for thiamine determinations.
T h e carotene concentrations were evaluated with a Coleman Universal spectrophotometer using a wave length of 455 millimicrons and a 20 x 40 mm. optically ground glass cuvette. Sincc no saponification step \vas included and since 1Iackinneg ( 1 7 ) stated t h a t some peaches contain xanthophyll esters F\-hich, like the carotenes, are n-ealily absorbed, the question arose concerning the accuracy of the carotene values of the peach samples. Comparative determinations w r e therefore made on samples from both lots of peaches to study the effect of saponification tiy blending the sample for 5 minutes with 12% alcoholic potassium hydroxide 11.9). T h e loirer values obtained for carotene aftcr saponification indicated t h a t the presence of xanthophyll esters in the unsaponified estracts gave falsely high carotene values; t h a t in the case of the clingstone variety the values were approximately doubled by the presence of these esters; and that in tlic case of t h e freestone variety the very low pigment value previously obtained as entirely accounted for as xanthophyll esters. I n this last case, storage effect on carotene alone would not have been measurable, and even in the case of the clingstone peach the storage changes !rere so small t h a t they viould have been more or less completely masked by experimental errors in thc isolation of carotene. Nr.icrs. T h e assay method of Snell and Wright (26) n-as used with the modified medium of Krehl, Strong, and Elvehjeni (24) changed a s follom: T h e biotin [?as increased tvxntyfold and t h e pyridosine \vas doubled. T h e samples were set u p in duplicate a t five levels. I n making digests, lG grams of the tomato juices arid tomatoes and 25 grams of peaches were autoclaved with 1 S hydrochloric acid in a volume of approximat,ely 200 nil. Since other5 ( 1 2 ) had reported using 1 a\- sodium hydroxide for hydrolyzing samples, a comparison was made betlveen acid a n d alkaline hydwlybis for each food analyzed. I n each case t h e acid-hydrolyzed saniplc gave slightly higher (7-127,) results. -1sa check on the assay, standard recoverim were determined on each run for each different type of food material. Only such values were accepted as agreed within 10% on three to five levels and for which the standard recovery n-as found to fall betireen BO and l l O ~ at o three to five levels.
t
g 80
70
- _- _
- L -
ORANGE JUICE
LL
0
- .__ ------_____
80
.
\.
a 80-
8 70-
\.
- - - _-'.\ .
3 6050-
E 40-
\. ,'
z
~
..
-..
LL
I
301015 Figure 2.
4
...... - .... ...... ..... . . . .
.. .
----
--- __ -----_-
-. '.
GRAPEFRUIT JUICE
ASSAY METHODS
CAROTESE.The met'hod used combined the extraction method of Moore and Ely (18) and t h e chromatographic technique of Wall and Kelly (27) with slight modifications a s used in some essays b y Hinman et al. ( 9 ) .
- - - -- - .-
I
'.
'.
\
12 MONTHS I N STORAGE
8
, I
18
Effect of Storage Time on Ascorbic Acid in Grapefruit and Orange Samples
996
INDUSTRIAL AND ENGINEERING CHEMISTRY
0
5 "1
i
TOMATO JUICE
z
o
1
w
+
W
I
I
k! 8
4
0
12 8
8
MONTHS IN STORAGE Figure 3.
Effect of Storage Time on Carotene
REDUCED .%SCORBIC ACID. The photoelectric nieasuremeni was used for the reduction of 9 ml. of indophenol dye by 1 ml. of
Vol. 39, No. 8
espcrimvnt readings were made tr-ith the !Lvelyn photoelcctric colorixnrter 5 and 10 seconds .after the reduction of the dyc, anti t,he results v x r e compared with tho 15- and 30-second readings of the same estracts on the Coleman Pniversal Spectrophotometer. This \vas done brcause evidenccx has bticn given (6') that mtrapolation of 5- and 10-sc.cond riwdirigs to zero time eliniinatcvl more coniplc,tely thia effect of ferrous ions. T h e comparative ascorbic of rsperimcnts arc' s l i o ~ r i acid value3 ohtained in thee tlvo in Tahle I. Tlicw resultb It'd t u the. cwnclusion that ttir ronwntratiori 01 ferrous ions in thesc canned fruits, c'vt'n after 1 1-month st orag?. \vas so l o n ac t o m a k ~i t s effect in..ipnifirant in oxalic acid 1'stract$. y- l i t t h e ranrietl juiu,? tiupliciitt. 1.5- ( ( I YO-gian~ sainp1t.s w w taken; for toitiatoc~s,grapcafruit srgnir*iitr,and pinvapple, 200 granis; arid for peaches, 300 granis n I n blending these samples thc conwntration of the oxalic acid used n-as varied as described ( 9 ) . I n the cases of the peaches and ~ of ascorbic acid, the pineapplrl, bccausc of the l o concentration filial dilutions 11-ere macle in the original blending, and the concentrations of oxalic acid employed were 1.5 and 0.75%, r w p w tively, to obtain pH values approsimating 1.6 in the filtrates. A few comparative experiments were niadr using 1, 2, 3, and 5 minutes for extraction of both pineapple and peaches. It was found that the extraction in 1 minute was as crimpleti, as that with longer time.
unbuffered acid-extracted sample ( b ) , a s applied to vegetables and fruits by Loeffler and Ponting (16) employing oxalic acid
($0). However, i t rvas knom-n t h a t ferrous ions reduce the dye in the presence of metaphosphoric acid (6,11,28)and presumably would also in oxalic acid in which the oxidized ferriosalate coniplex forms; also, the possibility esisted t h a t the ferroup ions might accumulate in stored canned foods. Consequently it \vas cwnsidered necessary t o learn whether the reduction of the (1)-e b y those ions mas being included in experimentally Yigiiificmt amounts. T o do so, parallel determinations were niade with S%, acetic acid ( 6 ) on the samples which n-ere assayed after 4 and 8 months of storage. On the ivhole, the values obtained a-ith acetic acid were loiver b y less than lo%, although in about one eighth of the cases they n w e identical or slightly higher. n i t h the peach samples, hoTvever, the values obtained with arc.tir acid were always loiver (9-30%). To determine the extent to which the l o w r valuer. uhtainrd with acetic acid extracts, resulted from the production of dehydroascorbic acid during hlcnding and filtering with this Icsi protective acid, a feiv csperinientb were carried out in Jvhich total ascorbic acid determinations x t w rnade b y thP Roc. inrthod ( 2 1 ) . acetic acid and mttaphosphorir acid cstrarts of one samplrx each of tomato juire and peaches, storrd for 11 munt ti3 a t 80" F., anti act'tic arid cwracts of pinPapple, stored at 50" F. for the same length of time., Tvere L W ~ . The values ohtained were c for riduced ascorbic acid on t h e s:me filh values on oxalic acid e s t i ' a e t ~of th(, samc saniples dctcrmined by t h r dye method. JIoreovcr, to study the question of the prwencc of icwouq ions further, the folloxing additional esperiment ivas run wit11 thwe same acetic, metaphosphoric, and oxalic acid estracts. In this
TABLE I.
COMP.iRISOS O F
R E D ~ C EATE D Twr.iL
.\S('(IRBIC
W
4 MONTHS IN
a
Extractant acid Acetic Oxalic Metaphosphoric
15.4 15 0
15.3
10 0 16 8 16.4
17.1
.,.
16.0
___~____ Ilediiceil i d y e ltlC thod) ~15-30 5-10 aec. SIX.
5 0
!.:
4 2 6 3
. .
Total (Roe) 6 6
. .
12
Figure I. Effect of Storage Time on Niacin -X-X-X-
-0-0-0-
50" F. 65' F. 80' F.
l l o r w l l ' 1 9 ) anti other3 h a w * u g g w t ( d the r~alrulatioiiof total volumr of estract as water of sample plus volume of estractant used. Thus, to calculate the so-called total volume of the estracts of pirieapplc, tomatoes, and grapefruit segments, moisture deterniinations of these foods n-ere made ( 1 ) and used. For the peaches, hccause the proportion of sample \\-as a t a masimum and moisture at a minimum, i t n-as thought that a brtter procedure nould h t o relate the 1-nil. aliquot of filtrate u v d in the reaction to the whole estract on a Iveight, rather than volume, basis. ' Therefore specific gravities of the filtrates . of both lots of peaches were determined. 'To calculate the total volume of exh C I D VILTES tract for each of the canned ,juices, the Peaches volume of cstractant and the volume _. Reduced of the sample x e r e added. Since sam( d y e method) --____ plcs were taken by neight, their volumes 15-30 5-10 Total see. see. (Roe) were based on their respective specific 1.9 2.1 4.3 gravities. 3.5 3 6 ... RIBOFL~T.IS. Both chemical and 3.5 3.7 4.3 mirrohiologiral mclthods wpre ustd. 7
Tomato juice Reduced tdvr " I ~ t I i P r i ~ 15-30 %10 Total sec. see. (Roe)
8 ST OR AGE
997
INDUSTRIAL AND ENGINEERING CHEMISTRY
August 1947
in which retention of ascorbic acid in the two Texas grapefruit
TABLE11. ASCORBICACID, CAROTENE,SIACIN, RIBOFLAVIN, juices stored a t 45 70 O, and 98' F. was followed for a period of %UD THI.%\fINE CONTENT O F CASSED FRUITS AND FRUIT JUICES 18 months, are included in Figure 2. The data for the warehouse BEFORE STORAGE storage study are given in Table 111. Comparison of the average O,
Canned Food C7rapefruit juice Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Grapefruit segments Orange juice Sample 1 Samnle 2 Sample 3 Peaches, halved Freestone Clingstone Pineapple juice Sample 1 Sample 2 Pineapple, diced Tomato juice Sample 1 Sample P Sample 3 Tomatoes, whole Sample 1 Sample 2 3ample 3 Sample 4 Sample 5
Ascorbic acid
.11illigrams/100 Grams CaroRiho...-_ Niacin flavin tene
-
...
45.5 40.6 35.6 36.6 32.2
0.043 0.040
. . . . ,
0.040
...
.
...
...
... ...
29.4
Thiamin?
...
...
...
0.095 0 092 0.070
38.2 38.2 49.2
...
...
...
. .
2.9 4.9
0.10 0.24
4 5 6 5
,.. ,..
0: 008
11.0 6.0 6.5
,..
...
. .
...
... ...
,
,..
0 056 0.050 0.082
17.5 18.4 24.4
0.42 0.58 0.62
8.4 8.9 8.5
0.032 0.02: 0.023
0.056 0.063 0.054
17.3 20.1 24.5 18 3 22.4
0.54 0.62 0.55
8.3 9.2 8.5
0.025 0.026 0.025
0.078 0.069 0.064 0.060 0.060
...
...
...
.
...
,
.
...
...
...
111 the chemical determinations, since thiamine also \vas to he ascertained on the samples, the double adsorption method of Conner and Straub ( 4 ) was used employing modificationP in digestion, length of columns, internal standards, and blanks 10). Because of the very low riboflavin content in tomatoes, interference with adsorption seemed t o be significant as the percentage variations between duplicate determinations were often over lo%, and good standard recoveries were difficult' to obtain. The microbiological assays had given slightly higher (+lo%) results in some comparative experiments; consequently it was decided to use this procedure for all assays after the 4-month storage determinations. For t,hose samples on which both types of assays had not been previously carried out, values obtained with microbiological determinations on preserved blends were used as initial values. I n each case t'hese blends had been preserved from the initial sampling or that of the 4-month 50" F. storage. The microbiological assays were carried out by the method of h e l l and Strong (24). THIAMINE. The thiochrome technique of Hennessey (8) \vas employed with modifications which have been described (9). ~TATISTIC.ALTREbTME1C.T. .Inalyses of variance (83)xere calculated for the vitamin retentions where there was doubt as t o the signifieance of the variations found with time and temperature of storage. The method suggested by Baten ( 2 ) for analyzing "degrees of freedom" in comparisons was used, since the "classes" did riot contain the same number of items. Where the calculated F value showed the treatment' variances t o be significant, the t test was applied to determine the significance of the differences between the means of the various time and of the various t,emperature intervals. Those differences found significant a t t,he 5% level ( P = 0.05) are reported as significant anti those at the 1% Icvel f P = 0.01) as highly significant,.
RESULTS AND DISCUSSION
The values for the vitanlinx determined in the canned foods before storage are listed in Table 11. These are within the range previously reported for each food analyzed (9, 18). The percentage retentions of the five vitamins under the controlled-temperature experimental condit>ionsare shown in a condensed form in Figures 1 t o 6. The avrrage r e d t s from the earlier experiment,
temperatures from records made in the different warehouses showed that the highest temperature (80' F.) chosen for the controlled temperature experiment extended slightly above the highest average temperatures existing in any of the warehouses included in this study, even those in the southern states, whereas the lowest controlled temperature (50" F.) was well below any average natural condition. ASCORBIC ACID. There was an excellent ret,ention of ascorbic acid in all canned fruit and fruit juice stored a t 50" F. for 12 months and in grapefruit juice held as long as 18 months a t 45' F. (Figure 2). These findings agree with those of Guerrant et a2. (7) for canned tomato juice, lima beans, and whole kernel corn. The retention a t 65' F. was also good. The data on the retentions of ascorbic acid in both peaches and grapefruit juice were treated statistically. The lower retentions in peaches (Figure 1) stored at, 65' F. were not found to be significant,,whereas the ones for the grapefruit juices (Figure 2) proved to be highly so. With the grapefruit juice any variation in means, for the different treatments, greater t,han 2.2 milligrams was found t o be significant, and t h a t of 3.1 milligrams highly so. T h e difference between the means for the 4-month 65' F. storage sample and the original assay mean was 3.5 mg. There was no further loss after 12 months of storage a t this temperature. I n the warehouses maintaining yearly average temperature of 65 ' F. or below the retentions of ascorbic acid in orange juice and tomatoes were exrellent.
TABLE 111. COMPARISON OF EFFECT OF WAREHOUSE STORAGE AND COSSTAXT TEMPERATURE STORAGE FOR 12 MONTHS ox -4sCORBIC
ACID
Const. temp chambers, UNV. of Chicago No. I Ko. I1
No.I11
New Orleans Tampa Tempe Y u b s City Oakland Washington,
D.
c.
St. Louis Rochelle S e w York
AND THI.4iLIINE I N
80 65 50 77
OR.4SGE
66
56198 54-91 50-92 54-104 51-87
76 92 97 73 81 81 86 92
63 61 59 58
42-79 36-87 28-92 30-78
91 91 90 96
77
72
io
JUICE AND T O h f A T O E S
%2 93 95 92 100 105 102
89 98 100 96 95 99 99 96
a2 93 94 83 79 89 88 86
101 101 98 106
103 95 99 98
90 89 89 96
83
a Average of two lots in constant temperature storage; only one lot in warehouse storage. b Average of three lots in constant temperature and of two lots in a a r e house storage.
K i t h 80" F. storage the greater losses in grapefruit juices Mere found to be highly significant after 4 months and those in peaches after 8 months. T h e average ascorbic acid loss in the several groups of foods held a t 80? F. increased in general with time. .It 8 months the losses ranged from 5 to 25% and a t 12 months from 10 t o 30%. Within this 12-month range the food groups can be ranked in the following order with regard t o losses: pineapple juice, tomato juice, and tomatoes least, 10 t o 20'%; citrus fruit juices next, about 20 to 25%; and grapefruit segments, peaches, and sliced pineapple most, about 25 to 30%. K i t h every type of food analyzed, results of the 8- and 12month storage assays showed, as is often predicted, that a n increase in storage temperature results in a n increased loss of vitamin C. T h e rate of loss was disproportionally higher at the higher temperatures. This was brought out even more clear13
Vol. 39, No. 8
INDUSTRIAL AND ENGINEERING CHEMISTRY
998
by the additional experiment on grapefruit juice, in which samples held a t 98" F. showed retentions of ascorbic acid of 75, 54, and 31% after 4,8, and 12 months, respectively. I n the other grapefruit juice samples stored a t 80" F., the retentions were 88, 70, and 75%, and at 65' F. they were 91, 91, and 90%, respectively, for the same storage intervals (Figure 2).
I-
w
4 8 MONTHS IN STORAGE
12
Figure 5 . Effect of Storage Time on Riboflavin 503 -_-_-_ 6j0 F. _ - - - _ _ _ 8O0F. _ F.
In the two samples of orange juice and three of grapefruit juicc, stored a t 80" F. for 12 months the variations in retentions were slight; they ranged only from 73 to 777,, with a n average retention of 75%. Ross also reported (2s)a 75% rct'ention of ascorbic acid in orange juice after a year's storage a t approximately 75" F. I n the two lots of Texas grapefruit juice stored at 70" F. (room temperature) for the same time the retention was found to be 85% (Figure 2). Orange juice held for 1 year in the t h r w n-awhouses having average temperatures of the order 72--77" F. (Table 111) retained its ascorbic acid to approximately the saim' extent, 81 to 737,. CAROTENE. This provitamin seemed entirely stable in tomatoes, tomato juices, and peaches stored at 50" and 65' F. for 1 year (Figure 3). Temperature effect was decidedly k>ssstriliing than with ascorbic acid, for tomatoes shoned no statistieally significant loss even at 80" F. Homver, peaches stored a t 80" F. for a year retained only abeut 867, of their original pigment value as assayed. Nrac~x. Niacin appeared to be quite stable in peaches (Figure 4) and tomato juice, as it was not adversely affccted by the experimental conditions regardless of time or temperature oi storage. There was practically no variation b e t w e n thc rctentions found a t the different temperature levels of each storage interval. This was also true for whole tomatoes; for thcsc', however, a n analysis of variance of the niacin retentions shoned R highly significant difference with increased time of storage. Application of the t test showed any difkrence greater than 0.51 mg. from the initial mean of 8.61 mg. was highly sigiiificant. After 8 months of storage the difference betlveen the means was 0.54 mF., and after 12 months, 0.68 mg. The average retentions, however, of all tomato and tomato juice samples for each storage period and temperature were never lower than 95%. RIBOFLAVIN. Some tomatoes and tomato juices seemed to show a small loss in riboflavin after 8 months a t 80" F., and by 12 months about half of the samples showed lowered retentions, around SOY,, at all three temperatures. However, because of the difficulties discussed under methods, there is a question as to the significance of this apparent loss of riboflavin. Although all retentions were based on microbiological assays, beginning a t the 8-month period, it was found that, in the long run, these gave no more consistent results (Figure 5) than did the earlier fluorometric results. The difficulties with precision in either type of riboflavin assay in tomato products no doubt resulted from the extremely low riboflavin contents.
T H I a u r x E . There was no apparent loss in thiamine in any canned fruit or fruit juice stored a t 50" and 65O F. for a period of 8 months. I n 12 months, however, a t both of these temperatures several products may have suffered slight losses, not exceeding 79" on the average. The statistical analysis on thiamine retention in tomatoes proved that the 6 and 77, variations at 50" and 65" F., respectively, after 12 months of storage were not significant. The highest temperature of storage definitely affected thiamine retention. In every case the samples stored a t 80" F. for both the 8- and 12-month periods gave the lolyest results. The 917, retention in tomatoes stored a t 80" F. for 4 months (Figure 6) was not found to be a statistically significant loss, but those of 87 and 827, after 8 and 12 months, respectively. proved to indicate highly significant, losses. After a year's storage a t 80" F. the thiamine retentions in related groups of products averaged 91% for citrus fruits and fruit juices, 887, for pineapple and pineapple juice, 837, for tomatoer; and tomato juices, and 817, for pcachcs (Figure 6). There was excellent agreement bctween percentage retentions for individual samples of the samc product. The rcsults from the warehouse-stored samples correlated well with these (Table 111). The percentage retentions of thiamin(, in orange juice as practically complete, 95-100%, b u t that in tomatoes stored in thc various ~varehousesfor a year ranged from 7Ioore, L. A , , and Ely, It., ISD.EKG. CHEM., A K A L . I;D., 13, 600 (1941). Morrell, 8 . A , , Ibid.. 13, 793 (1941). Ponting, J. D., I b i d . , 15, 389 (1948). Roe, J. H., and Oesterling, >I. J., J . B i d . Chen., 152, 511 (1944). Ross, E.. Food Research, 9, 27 (1944). Snedecor, G. IT., "Statistical Methods," 4th ed., Ames, Iowa, Collegiate Press. Inc., 1946. Snell, E . E.. and Strong, F. X I . , IND.ENG.CHEM.,AKAL.ED.. 11, 346 (1939). Sriell, E. E., and Wright, L. D.. J . B h l . Chem., 139, 675 (1941). Wagner, J. R.. Ives, %I.. Strong, F. XI.. and Elvehjem,C. A.. Food Research, 10, 469 (1945); Wall. M , E., and Kelly, E. G., IND. EKG.CHEX.,h s . 4 1 , . ED.,15,
1s (1943) TVoessner, 1%'.W., Elvehjem, C. A , , and Schuctte, H. h.,J . .\-cctrition, 20, 327 (1940). I
ACKNOWLEDGMENT
This work was iupported in part by a grunt from the Sational ( h n i i ( w Association-Can 1Ianufact urers Inst itutr Sutrition
I N partial iulfillrnent of the requirements ior the degTee of doctor of 'Osoph). by Dorothy S. Noschette
phi-
