Vitamin Content of
J
ted
EFFECT OF PACKAGING AND STORAGE Dehydrated fruits atid ,egetablea packaged in metal containers in an inert gas, in air, and in paper cartons, and stored a t room temperature, 98" F., and 130' F., have been atudied with regard to vitamin atabilit? over a storage period of one )ear. The beneficial effect of inert gas packaging on carotene and ascorbic acid has been overahadowed by losses due to elelated temperatures of storage. Increased storage temperature had a detrimental effect on thiamine retention. Riboflavin in dehydrated products appears to be quite stable.
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6. HEBEMLEIN AND L. E. CLIFCORN
Hesearch Department, Continental Can Company, Inc., Chicago, Ill.
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n' 1942 Howe (2.2) einpha-iztd that dehydia-
tion processes had not progiessed far enough to make the products reliable sources of xscorbic acid and carotene or vitamin A. Many questions regarding vitamin atability have subaequently arisen during the rapid growth of the dehydrated food industry. Information has been lacking on the effect of packaging and storage on the stability of vitamins in commercially dehydrated foods. Two aspects of the problem will be considered here. First, what effect do various types of containers or packages and gas packing have on the quality and nutritive factors in dehydrated foods during storage? Secondly, how do increased temperatures of storage influence these variables? Packaged dehydrated food should be able to withstand temperatures varying from subarctic t o equatorial, as well as moisture changes from arid desert to humid tropical. I t has been estimated that the average Army storage period for dehydrated foods is nine months, Elem the dehydrator to the mess kit, The scarcity of puhlished information on this
d: , 4 0
+ Figure 1. Effect of Gas Packing on Ascorbic Acid B Cabbage (4.0% HzO); 0 tomato juice coektail;
-
Q cranberries.
Nitrogen pack;
- - -paper carton.
4 Reduced acid room-temperature storage. I#: Reduced acid: 98' F. storage.
S T O R A G E T I M E IN MONTHS
C. Total acid, room-temperature storage.
912
INDUSTRIAL AND ENGINEERING CHEMISTRY
October, 1944
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S T O R A G E TIME IN M O N T H S Figure 2. Effect of Gas Packing on Carotene
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0 Carrots (5.6% &O); H carrots (4.6% Hi0); 0 tomato juice cocktail
Carbon dioxide -aaok:. .i. Room-temperature storage. R. 98" F. storage.
vack.
subject is due in part to the lack of interest in most, dried foods during the period following World War I, and also to limitations of vitamin methods at that tjime. Tressler (df) and Cruess ( 7 ) in a review of the literat.ure t'hrough 1941-42, observed contradictory data on the vitamin A or carotene and ascorbic acid values of dehydrated foods. Tressler found no reliable dat,a on the effect of storage on the B vitmiins in dried fruits and vegetables, but hoth reviewers concluded that. the lossw s o u l d probably be greatest during dehydration. Chace (4) stored carrots, cabbage, and sweet potatoes at 90" F. in air, nitrogen, oxygen, and carbon dioxide, and found maximuni retention of carotene in nitrogen and, to a lesser extent, in carbon dioxide. Ascorbic acid in cabbage seemed to be best retained iii nitrogen while no significant changes in thiamine or riboflavin were observed. Farrell and Fellers (11) found that dehydrated green beans ret#ained98% of the original thiamine after dehydrat,ion with an over-all retention of 8401,after one year of storage at, 38" F. No changes in riboflavin were not#ed,but only 5% of the original ascorbic acid remained after dehydration and 4% after one year of storage at 38" F. Wall and Kelly ($3) observed the disappearance of large amounts of carotene from several varieties of dehydrated plant materials on 3-6 month storage at room temperature. Aykroyd (1) found a 50% retention of ascorbic acid in cabbage, cauliflower, and knol-khol, stored 12 weeks at 98.6" F. in sealed containers. He also found only 2530% retention of that vitamin in the same vegetables stored 6 weeks at 64-73" F. in unsealed containers. Dutton et al. (10) stored dehydrat.ed spinach for 32 weeks under several ex-
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91 3
perimental conditions, and correlated the chlorophylI, carotene, and ascorbic acid content. They found t h a t carotene retention was decreased by oxygen in t h e storage atmosphere but was Unaffected by moisture content. Davis el al. (8), studyingfactors affecting the quaIiiy of a few laboratory-dehydrated vegetables, concluded that storage temperature was of prime importance, adequate blanching second, and the atmosphere of the package third. I n an extensive study of fourteen laboratory-dehydrated vegetables, stored 6 months a t 70" and 98" F.,Beardsley et al. (2) observed that retentions of ascorbic acid and carotene were decreased considerably by the presence of oxygen in the storage atmosphert,. Thiaiine was unaffected, but its retention was appreciably decreased by increase in storage temperatures, as was retention of ascorbic acid. Storage temperature had no consistent effect on carotene. In a study of the nutritive value of three commercially dehydrated vegetables-cabbage, potatoes, and turnipsDavis and MacArthur (9) reported that carotene and thiamine were quite stable during dehydration but ascorbic acid was not. They also reported that storage temperatures above 65-70' F. and oxygen in the storage atmospheres were detrimental to the retention of ascorbic acid. Carotene retentions were best in an inert storage atmosphere; thiamine was quite stable after 36-weeh storage a t high temperatures (not above 100' FJ, regartiless of storage atmosphere. Tressler et al. ($$), working with commercially dehydrated cabbage, beets, potatoes, and rutabagas, observed the effect of dehydration and storage on the carotene, thiamine, and ascorbic acid contents of those vegetables. In the main, their findings substantiate those of Davis and MacArthur although tho latter's range of storage temperatures was slightly higher IJsing a bioassay method, Scoular et al. (18) found that pulverized dehydrated sweet potatoes retained 83% of the original vitamin A potency after one-year storage ~t ronm temperature. PACKAGING, STORAGE, AND ANALYTICAL PROCEDURES
The object of this xork was to obtain informat'ion on comnercially dehydrated products and, wherever possible, to duplicate commercial packaging conditions, With the assistance af thc Subsistence Research Laboratory of the Quartermaster Corps, samples of eleven freshly dehydrated fruits and vegetabrcs were obtained from the production lines of several food processing plants. To study the effect of lower moisture contents of dehydrated foods on vitamin stability, portions of the same lots of dehydrated beets, cabbage, and carrots were further dried in a small dehydrator a t the New York State Agriculture Experiment Station. The moisture levels were thus lowered another 1 to 1.5(%. Information on the dehydrated foods used is shown in Table I. As rapidly as possible all products were packaged in an inert atmosphere and shipped to the laboratory if sample containers were not available a t the source of the product. When nrwssary, the product was repackaged so that four commercial (widitions of packing were simulated for each product. Three packages were the conventional hermetically sealed metal containers; one had an atmosphere of air, one had carbon dioxide, and one had nitrogen. The latter two conbainers were packed with as low an oxygen content as was commercially feasible. A vacuum pack was not prepared since the usual commercial size container is too large (due to dangers of collapsing). The fourth package was an Army substitute 3-111-1 paper container supplied by Reynolds Metal Company; it consisted of a three-ply kraft paper-lead foil-cellulose envelope, heat-sealed and enclosed in a paper carton. Units of each of the packages mere then stored a t three different temperatures-namely, room temperature (7580' I?.), 98", and 130"--with one exception. The substitute paper package only (98' F.) y a s stored in an atmosphere maintained a t 93% relative humidity. Sufficient units were stored a t t'arh t)emperatbre to provide samplea a t intervals of 2 weeks,
INDUSTRIAL AND ENGINEERING CHEMISTRY
914 I
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followed by 24hour incubation with an enzyme mixture of clarase and papain. Complete tables of vitamin values are being published elsewhere (6).
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CORRELAFION OF \ARIABLES
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3 Tomato juice cocktail; 1 carrots (5.6% HzO); 0
H2Oi. --(4.9% StOI'dgC: - - - 98' - -Room - 130'temperature F. storage. 4.
Nitrogen pack.
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The vitamin values presented here were obtained by the methods described and should probably be called "apparent" vitamin values, since for stored dehydrated foods the correlation t o biological activity is, in most instances, unknown. At the higher storage temperatures and after long storage periods, significant quantities of interfering materials were present in the determination of ascorbic acid, which appeared as an "apparent" synthesis of ascorbic acid during storage. This may be explained by the formation of reductones and perhaps other reducing substances. The significance of the dehydroascorbic acid determination has been questioned by some workers. The Roe dinitrophenylhydraLine method has been tried with results of questionable Yignificance, and further work is necessary. Mapson (IS), Wolres et al. (,%$), and Melville et al. (16) have observed interfering reducing materials in dehydrated foods and other products, and suggested ways of correctmg for these interferences by employing formaldehyde It is planned t o make ascorbic acid determinations on some of the samples included in this study by other methods such as electrometric titration, ascorbic acid oxidase, and formaldehyde condensation procedures in arder t o obtain a more correct value for the true ascorbic acid content. Portions of the ascorbic acid curves which have been particularly affected by apparently excessive amounts of intm-fering materials in 1 hc later periods of storage are indicated hy dotted hnrs
beplr.
F. storapn,
B . Cnrhon dioxide pack.
1, 2, 3, 6, 9, and 12 months.
Initial examinations werv made a t the time each product y a s placed in storage!. Quality factors are reported elsewhere (6). Measurcrnents of the nutritive factors of t,hese samples are dcscribed here. Attention is focused on ascorbic acid, carotene, thiamine, and riboflavin. hnalyses were not made for factors occurring in insignificant quantities in the products included. Reduced ascorbic acid vas measured by the Morel1 modification (1?) of the Hessey (3)technique; a (loleman Model 11 spectrophotometer was used, and galvanometer readings were t,aken a t 15- and 30-second intervals. Dehydroascorbic acid was estimated by reducing all oxidized ascorbic acid with hydrogen sulfide and measuring the total reducing power as recommended hy Bessey (3). The color and turbidity of the extract of cranberries made it, nrcensary to measure the ascorbic acid of this product by a modification of the Stotz procedure ($0). The dye is permitted to react 15 seconds, dxcess dye is extracted with xylene, and the concentration of dye is measured on the spectrophotometer. Carotene was estimated by the modified chromatographic procedure of Moore (I5), using Moore and Ely's method of extraction (16) and substituting denatured alcohol for ethyl alcohol in the foaming mixture. Thiamine was measured by the thiochrome method, as modified by Conner and Straub (5),in a Colem?n Model 12 photofluorometer. Riboflavin was determined by the Snell and Strong microbiological method (IQ), modified by use of acid extracts neutralized to pH 4.5. with sodium ncc.tat,e aftrr autoclaving; in most cases it was
---+ Figure 4.
---
._ICarrots
Effect of Storage Temperature on Carotene (5.6% HaO); 0 tomato juice cocktail.
Room temperature storage: 130* F. storage.
A.
Vitrngen pack.
El.
- - - 9S0 F.
Paper carton.
atorago;
STORAGE
T I M E IN M O N T H S
INDUSTRIAL AND ENGINEERING CHEMISTRY
October, 1944 Figure 5.
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Effect of Storage Temperature on Reduced Ascorbic Acid
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tomato juiee cocktail. 'ICabbage (2.9% H20); Room t e m p e r a t u r e storage: 98' F. storage; 130° F. storage. 1. Nitrogen pack. H. Paper carton.
+
Interferences were noted in the thiamine determinations of beets and onions. Increases in apparent carotene content were noted in some of the samples of carrots after one year of storage. Biological assays of stored dehydrated carrots are planned, as well as chromatographic studies of the decomposition products of carotene and of the extrart determined as carotene by the Moore method. The values obtained represent maximum vitamin contents, and the best analytical methods available a t the time were used. Although the dehydrated foods lost much of their desirable flavor, color, and other quality characteristics upon storage a t elevated temperatures, vitamin analyses were continued until the product was found t o be unacceptable. The storage life of each product from the standpoint of arreptability is shown in Table IT.
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EFFECT OF GAS PACKING
The effect of packaging in inert atmospheres (carbon dioxide or nitrogen) and its relation to retention of ascorbic acid and carotene in three representative products are shown in Figures 1 and 2. No significant differences in thiamine and riboflavin were noted that could be attributed t o the presence or absence of oxygen in the package. Figure 1A shows the difference in the reduced ascorbic acid levels of the nitrogen and paper carton package at room temperature, and Figure 1B shows the same variable in these samples a t 98" F. The effect of packaging on the apparent total ascorbic acid (reduced plus dehydroascorbic acid) level a t room temperature is shown in Figure 1C. Results with the carbon dioxide package could be substituted on the graph for the nitrogen pack, and would give practically
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S T O R A G E TIME IN M O N T H S
TABLE I. LIST OF FOOD PRODUCTS AND DEHYDRATION PROCESSES Product Apple nuggess Beets Cabbage Carrots Cranberries Irish potatoes Rutabagas Tomato flakes Tomato juice cocktail
Variety Unknown (northwestern U.S.) Detrpit Dark Red Danlsh Ball Head Red Core Chantenay Unknown (Cape Cod, Mass.) Unknown (Idaho) Yellow Swede Unknown (N. Y.) Unknown (Calif.)
Form Coarse ground slices Diced Shredded Diaed Pulp Julienne Diced Pulp Pulp
Blanch
Min. ,
7
.
4a/4
61/2
flit 1 .. ..
O F .
Type
$40 205 240
Steim Steam Steam
206 210
Steam Water
....
Finishing % Dehydration" Temp., Final Time, Hr. O F. Moisture 2 vacuum 0.8 4: tunnel: 18, finishing bins i40 4.9 & 3 . 7 7 135 4 &2.9 5. tunnel: 18, finishing bins 130 5.6 & 4.6 Drum-dried 2 9 iio 7.1 5 7 3.8 Drum-dried .. 1 . 6 Drum-dried 3.3
....
.
Unless otherwise specified, dehydration was carried out in a tunnel dryer.
a
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TABLE 11. Product
Air 12 12
12 3
9 Cranberries Irish potatoes Rutabagas Tomato flakes Tomato juice cocktail 'I
b
'
3 3
3 6
96 9 9
STORAGE
LIFE OF DEHYDRATED FOODS (IN MONTHS), BASEDON ACCEPTABILITY"
Room Temp. Nt Cot 12 12 12 12 12 12 12
12 12 12
9b 9)
12
12
12
12 12 12 I2 12 9) 96 12 12
Carton 12 12 12 6
6 3 3 3
9 9b 9 1
Air
98' F. Storage Na COz
9 3 3 0.6
9 12
0.5 1 3
3 3
1 1
3
9 2
9
1 2 6 1
9b 9 2
9
9 9 2 2 3 3 6 1 96 9 2
Carton 3 3 3 0.6
1
0.5
I 1.5 1
6 6
1
Since the last examination was conducted a t 12 months the products so indicated ma? have a longer atorage life. Incomplete examinations; further storage may reveal the product is still acceptable.
Air 1
