Homogenized Liquid and Dried Eggs STABILITY OF VITAMIN A AND CAROTENOIDS DURING DEHYDRATION AND STORAGE S. M. Hauge, F. P. Zscheile, C. W. Carrick, and B. B. Bohren PURDUE UNIVERSITY AGRICULTURAL EXPERIMENT STATION, LAFAYETTE, IND.
Commercial homogenized liquid and dried whole eggs 90" to 120' F. The total HE demand for enorsolids of the individual sammous quantities of dried were sampled during a day's run. Spectroscopic studies ples of powder as tested in the of the carotenoid content and ultraviolet absorption eggs for military and indicated that sampling errors were small and that comLend-Lease purposes has plant varied from 96 to 98%. SAMPLING. .In order to posite samples were representative of individual samples. stimulated a rapid expansion minimize sampling errors Biological assays showed that losses of vitamin A potency in the dried egg industry. which might wise from variaduring dehydration were negligible. Storage for 12 months Although extensive studies tions in the vitamin A have been made upon the at 18"C . caused no loss of potency. The losses at 4-5" C. potency of individual eggs, nutritive value of fresh eggs, were small, At +20° C., room temperature, and warepaired samples of fresh liquid Little information is available house temperature, losses were appreciable after 3 months, homogenized eggs and of deon the nutritive value of dried but the rate of loss was greatly reduced during the next 9 hydrated eggs were collected months. Spectroscopic observations were parallel to the eggs. I n the program on every half hour during a 6 biological results, and also indicated no loss of vitamin A t h e c o n s e r v a t i o n of t h e nutritive value of foods, it or carotenoids during the periods of time required for hour period. The liquid Samples were drawn from the bybiological tests. Typical absorption curves of egg extracts is vitally important to know whether or not the nutritive pass of the homogenizer. The are interpreted in terms of vitamin A potent carotenoids. dry samples were taken value of eggs has been lowered during the dehydration proca p p r o x i m a t e l y 3 minutes ew and the extent of deterioration of the dried product during later as the dried eggs fell into the barrels for packing. From the samples collected on the hour (series A) definite quantities of the storage and marketing period. Since vitamin A is one of the each were taken and mixed into one composite sample of liquid most labile food factors, a study waa made of the effect of the eggs and one composite of dried eggs. Similarly, the samples dehydration process upon vitamin A potency of dried eggs and the retention of the vitamin during storage. collected on the half hour (series B) were made into composite samples. The total solids of the composite samples of the liquid During the progress of this investigation a preliminary report was made on the effect of dehydration upon the vitamin A conand the dried eggs were 27.4 and 96.3%,-respectively. I n order to test the uniformity of sampling, spectroscopic examinations tent of eggs (1). Later Klose, Jones, and Fevold ($) reported were made upon the two series of composite samples of liquid and on the vitamin A retention in dried eggs, using the antimony tridried eggs as well aa upon the individual samples. chloride method and biological assays. The present paper presents biological results with parallel spectroscopic obsenrations. STORAGE. From each of the two composite samples (A and B) of dried eggs, twelve portions of 400 grams each were packed in Mason jars. Three jars from each series were packed in cartons TREATMENT OF EGGS to exclude light and stored a t - 18' C., +5", +20', and room temS o m m AND PROCESSING. The homogenized liquid and dried perature. A t the end of each storage period (Le., 3, 6, and 12 eggs used in these experiments were prepared in a commercial months) one sample jar of each series was removed from each plant on May 4, 1942, from current receipts of fresh shell eggs carton and stored a t -18" C. for testing. In addition, composite samples of both series were packed in two small barrels (not over 12 days old) from central Indiana, Kentucky, Tennessee, and Illinois. The eggs (none of which were a t temperatures with double paper liners and left a t the plant for storage in the above 70" F.) were broken in the conventional manner with the warehouse. These were sampled at the end of 6 and 12 months. elimination of any objectionable eggs. The liquid eggs were All samples were preserved at 18' C. during the test period. transferred to a churn for mixing and then passed through a Hansen Liquid Egg Strainer into a cooled storage tank where the ANALYSES mix was held at 36" F. with agitation for a period not exceeding 8 hours. The mixed liquid eggs were homogenized and sprayed SPECTROSCOPIC EXAMINATION. For the spectroscopic obthrough eight double-opening nozzles of 0.042 inch diameter servations, samples were saponified and extracted with ether under a pressure of approximately 2600 pounds per square inch by the method described earlier for butterfat (7). Ten-gram into the chamber of the Mojonnier dryer, accompanied by preand three-gram samples mere employed for homogenized and heated air ranging in temperature from 370" to 380" F. The dried eggs, respectively. The weighed egg samples were recondryer was operated under slightly reduced pressure by means of stituted by moistening with 8 ml. of water for 1 hour at.room suction fans which removed the dried egg powder to the coltemperature before saponification. The photoelectric spectrolector; then it was sifted through screens and packed in barrels. photometer and spectroscopic methods were the same as those The temperature of the exhaust air leaving the dryer was 153" F. employed earlier in studies on butterfats (7) and vitamin A (6). The dried egg powder, iu i t came from the screen, varied from Wave length 3240 d. was considered best for vitamin A deter-
T
-
-
U
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VOl. 36, No. 11
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
1066
I t is clear from Table'IA that the spectroscopic deviations among the six samples are negligible. I n so far as these absorption measurements indicate uniformity of chemical composition, the composite samples are adequately representative of the individual samples. STABILITY OF EGGSAT -18' C. DURING BIOASSAY. Spectroscopic observations were made on composite samples at intervals during the fist bioassay period, with results presented in Table 1B. Differences for the same sample a t different times are approximately equal to those observed among different samples reported in Table IA. No trend in results was observed with increasing periods of storage. STABILITY OF VITAMIN A DURING DEHYDRATION. The results of the spectroscopic examinations (Table IA) and the biological assays show that little or no deterioration of the vitamin occurred during the dehydration process. The paired samples of liquid and dried eggs of series A were found to have potencies of 45 and 43 I.U. per gram, VITAMIN A ALCOHOL respectively; those of series B had 44 and 45 I.U. TOTAL CAROTENOIOS, HOMOGENIZED FRESH EGGS. t----. n n ,DRIE per gram, respectively, when compared on B * LIGHT-COLORED '* ----'' moisture-free basis. CAROTENOL F R A C T I O ~ , 19 * . Since the spectroscopic observations failed to reveal any deterioration of either the liquid or dried egg samplas during the assay period (Table 0 0 0 8 8 m0 0 0 IB), it is probable that no losses occurred in the m m m a m 8 liquid eggs during the assay period which might Were Length, A. compensate for losses in the dried eggs during Figure 1. Absorption Spectra of Egg Extracts in Ether Solution the dehydration process and assay period. Therefore, the biological values have added mination because the absorption maximum of vitamin A alcohol significance. These observations on the retention of vitamin in ether solution occurs at this wave length. Wave length 4370 diring dehydration are substantiated by work of Klose, Jones, A. was employed for estimation of total carotenoids for comparaand Fevold (8). tive purposes. Although the absorption of 8-carotene at this wave length is essentially unchanged by heat isomerization, no RETENTION OF VITAMIN A DURING STORAGE such definite information is available for the caratenols. The effects of time and storage conditions upon the vitamin BIOLOGICAL ASSAY. The samples were assayed for vitamin A A potencies and spectroscopic values of the dried eggs are shown by the usual rat growth method, using U.S.P. reference oil in Tables I1 and 111, respectively. These two series of results diluted with Wesson oil as a standard. To overcome the problem are approximately parallel. It is apparent that the samples of uniform sampling during the assay of the liquid eggs, the comstored at -18' and + 5 O C . , the usual storage and refrigerator posite samples of liquid eggs were broken down into weighed temperatures, respectively, retained most of their original vitamin portions of 25 grams each; these were stored a t -18' C. until activity; in the samples stored at the higher temperatures, conneeded for the feeding tests, when they were diluted to 500 ml. siderable deterioration had taken place although the losses of with 1% saline solution. For convenience in weighing the test doses, the dried egg samples were diluted with four times their weight of the vitamin A deficient diet. The vitamin A potencies of all samples were calculated upon a moisture-free basis. STUDYOF HOMOGENIZED LIQUIDAND TABLE I. SPECTROSCOPIC DRIEDWHOLEEGGS
- .... --
3
....
.
91
3
f
a 8
c
SPECTROSCOPIC EXAMINATION
UNIFORMITY OF SAMPLES. Absorption values are compared in Table IA for six individual samples of both the A and B series and for the composite samples. Much greater uniformity was observed a t 4370 8.than a t 3240 A., an indication of greater variations in ultraviolet absorption which involves vitamin A carotenoids, and miscellaneous substances, than in visible absorption due only to carotenoids. The deviations for dried samples were slightly higher than those for liquid samples. Changes induced by drying appear to be of little practical significance. Composite samples agreed well with the corresponding averages of the individual samples of liquid eggs. Agreement waa equally good at 4370 A. for dried eggs. At 3240 8.for dried eggs, discrepancies of about 7% occurred, in accordance with the greater deviations found in the ultraviolet region. The data on the dry basis also agree better at 4370 A. than at 3240 d. Slightly increased absorption in the ultraviolet follows drying.
3240 A. 4370 A. A . Sampled during a Day's A B A B 13.0 14.1 70.4 74.2 12.6 13.0 71.4 76.1 12.0 12.8 72.3 72.6 12.4 12.8 70.3 73.4 11.1 12.4 72.6 72.6 10.8 12.0 70.3 73.7 12.0 12.8 71.2 73.6
Ssriea
Sample 1 Sample 2 Sample 3 Sample 4 Sample 6 Sample 6 Av. Av deviation % ' M i x . deviatidn, % Composite samples Dry basis B.
0 days 23 days 61 days 106 days
?&,) x -01
(23: Homogenized liquid
6.8 3.6 10.1 12.3 12.7 46.0 46.4 10.0
Effeot of 12.3 13.6 12.6 11.2
1.2 1.0 1.8 2.0 72.8 73.9 266 270
Dried 3240 A.
4370 A.
Run A 63.0 44.6 43.4 46.4 41.9 46.6 46.8
B 46.7 46.3 46.7 41.7 44.3 39.6 43.9
0.8 6.2 11.8 9.8 49.0 47.3 60.7 49.0
-
Short-Time Storage at 18' 12.7 72.8 73.9 49.0 12.1 73.7 76.6 47.6 11.4 73.3 74.7 46.1 12.7 69.9 76.1 47.4
C. 47.3 46.7 48.2 46.1
A 268 268 269 263 264 267 206
B 276 204 209 264 2b9 261 204
1.3 2.2
3.0 4.6
263 261 272 270 263 266 263 260
261 271 264 266
November, 1944
INDUSTRIAL AND ENGINEERING CHEMISTRY
vitamin A potencies were not so great as might have been expected. The greatest losses were observed in samples held at room temperature, where the losses were about Myo in 12 months. The samples stored in the warehouse retained about 70% of their vitamin activity, which may be considered satisfactory. Klose, Jones, and Fevold (8) reported somewhat greater losses in then samples at comparable temperatures. This suggests that these variations may be due t o effects of difference in dehydration process or to effects produced by difference in the rations of hens producing the eggs. Table I1 shows that the rates of loss of vitamin A were greatest during the first 3 months, after which the vitamin appeared rather stable. S h i lsr deductions can be made from results of the bioassays by Klose, Jones, and Fevold (8). No explanation can be offered a t this time for the apparent inhibition of losses after 3 months of storage.
1067
4-
ABSORPTION CHARACTERISTICS OF EGG FRACTIONS
To permit a more critical study of changes during dehydration, more extensive absorption measurements were made. Typical characteristic curves of egg extracts are presented in Figures 1 and 2. The mme rm E values are plotted on a Iorithmic scale. Curves of identical substances are Figure 2. then superposable, regardless of concentration, through multiplication of the E :m, values by a constant, K. An attempt was made t o study vitamin A independently of other carotenoids. To this end lightcolored eggs were produced by hens on a special low-carotenoid diet. The yolks were very pale but not free of color. The carotenol fractions were transferred to ether from 90% methano1 solutions which had been washed with hexane.
1
8
s 0
8
8t
t
n t
p
q
A.
Wave ~en(rth,
Absorption'Spectra of Egg Carotenoids in Ether Solution
Figure 1 gives the ultraviolet curves in comparison with that of vitamin A alcohol. All curves were made to coincide a t 3240 A., the absorption maximum of vitamin A alcohol (6). Differences between the curves for fresh homogenized eggs before and after drying were small, an indication of little change during dehydration. These curves are very different from that of vitamin A, both in position of maximum and in shape. These differences are TABLE 11. EFFECT OF STORAQE TEMPERATURE AND TIMEON VITAMIN A due principally to the high content of other POTENCY OF DRIEDEQQS carotenoids. The curve for the light-colored -- 18O C,- -+So C.~ 4 - 2 C.-0 ~ -Room-e-Warehouaeegg more nearly approaches that of ,vitamin A, Stora e VitaVitaVitaVitsVitabut the presence of other carotenoids is indiPerioa, min A, Reten- min A, Reten- min A, Reten- min A, Reten- min A RetenSeries Months I.u.4 tion, % ' I.U. tion, % I.U. tion, % I.U. tion, % I.U. 'tion. % cated by comparatively high absorption near A 0 43 ,100 43 100 43 100 43 100 43 100 3800 A. The carotenol fraction was free of 3 43 100 41 96 29 67 32 74 6 41 96 36 83 29 67 96 68 a8 '6k carotenes but contained vitamin A; hence, 12 43 100 .. ... 30 70 27 63 32 74 slightly better agreement with absorption charB 0 46 100 46 100 46 100 46 100 45 100 acteristics of vitamin A was observed. 62 87 32 71 28 89 39 3 40 68 30 '67 80 28 62 24 89 36 6 40 I n Figure 2 the standard curve^ of all-trans 0 I .U.per gram of moisture-free egg. a-carotene ( 4 ) and @-carotene(6) are presented for comparison. Curves agree a t 4497 A., a STUDY 01. EFFECT OF LONG-TIME STORAGE ON TABLE 111. SPECTROSCOPIC wave length a t which the a- and @-carotene DRIED WHOLEEGGS AT DIFFERENT TEMPERATURESO curves intersect. I n general, the predominant -WarehouseStorage - 18' C -+6' C . 7 -+20° C.-RoomTime Absorp- Re'ten- Absorp- Reten- Absorp- Reten- Absorp- Reten- Absorp Retencarotenoid of eggs is lute01 (3),which has the Montds tionb tion, % tions tion, % tiona tion, % tionb tion, % tionb tion, % configuration of *carotene. Curves for fresh Wave Length 3240 A. homogenired eggs before and after drying were 0 48.1 100 48.1 100 48.1 100 48.1 100 48.1 100 3 47.8 99 44.2 92 40.3 84 37.1 78 identical, indicating little if any change in the 6 49.2 102 46.2 96 40.7 86 40.6 86 4i:l 87 carotenoias, even by isomerization, during d e 70 33.5 70 32.2 67 89 .. ... 33.6 12 42.8 90 .. ... 33.0 69 33.3 69 36.1 76 16 43.1 hydration. The close agreement between the Wave Length 4370 A. curves for total carotenoids and the carotenol 0 262 100 262 100 262 100 262 100 262 100 fractions of the light-colored egg indicates the 3 267 98 248 95 216 82 202 77 6 267 102 238 190 72 186 71 ibo 72 comparatively low content of carotenes in the 12 243 98 ., ..91, 160 61 168 60 166 63 yolk, particularly &carotene. 16 238 91 160 61 161 61 173 66 None of these curves can be analyzed as 4 These figurea are averages of the A and B aeries. binary mixtures of well-known pigments b X 1000. whose curves have been aorurately deter-
-- -
...
..
...
...
(Eig,)
//
INDUSTRIAL AND ENGINEERING CHEMISTRY
1068
mined. I n general, their shapes and pusitions of maximum absorption indicate that carotenoids of the alpha configuration predominate. Some cis-isomers are probably present as well as a low proportion of carotenoids of the beta configuration. T o study the relative amounts of different pigments in eggs, the total carotenoids of an egg yolk extract in ether were chromatographed on a 50% magnesia-Super-Gel adsorption column and developed with ether. Relative amounts of pi ent in each zone were estimated by use of wave length 4450 Only about 5% was in the filtrate or carotene fraction, the curve of which indicated high relative absorption in the region below 4300 A. The lower brownish-yellow zone contained 45% of the original pigment, which had a curve almost identical with that of alltrans a-carotene. It was probably luteol. The next zone contained a yellow pigment (15%), the curve of which also resembled that of all-trans a-carotene. The third zone from the bottom was red and contained a pigment (15%) which had absorption properties somewhat intermediate between those characteristic of the all-trans alpha and beta configurations. -4small red zone a t the top of the rolumn was not examined. The pigments of
Vol. 36, .NO. 11
these zones were not purified further.
I n the egg studied, over
75% of the recovered pigments were of the alpha configuration. ACKNOWLEDGMENT
The writers acknowledge with appreciation the assistance of L. F. Green, R. H. Harper, and H. A. Nash in the spectroscopic phases of this work, and of E. L. Johnson with biological assays. They are grateful to the hlidstates Frozen Egg Corporation for cooperation in supplying the eggs used in this investigation, LITERATURE CITED
Hrtuge, S. M., and Zscheile, F. P., Science, 96, 536 (1942). Klose, A . A.,Jones, G. I., and Fevold, H. L., IND.ENG).CHEM.. 35, 1203 (1943).
Kuhn, R., and Smakula, A., 2.phyaiol. Chem., 197, 161 (1931). Nash, H.A., unpublished work in these laboratories, 1943. White. J. W..Jr.. Zbid.. 1942. Zscheiie, F. P., and Henry, R. L., IND.ENO.CEBIM., ANAL.ED., 14, 422 (1942).
Zscheile, F. P., Nash, H. A,, Henry, R. L., and Green, L. F.. Zbid., 16,83 (1944). JOURNALPaper 178, Purdue University Agricultural Experiment Station
BATCH RECTIFICATION Yields at Finite Reflux Ratios R. EDGEWORTH-JOHNSTONE Trinidad Leaseholds Limited, Pointe-a-Pierre, Trinidad, B. W . 1.
A general method is described for calculating yields from batch rectification of binary mixtures under constant distillate conditions for any given final reflux ratio. The method allows for the effect of column holdup. Simplified equations are derived for both binary and complex mixtures which are applicable to certain cases in which holdup is negligible.
N EARLIER paper (a) described a method of calculating the final yield of distillate from batch rectification, allowing for the effect of column holdup, when the reflux ratio is continuously increased to infinity in such a manner as to keep the distillate composition constant. This was termed “batch rectification under constant distillate” (c.d.) conditions. I n the present paper a general method is presented for cases where the final reflux ratio has a finite value. This enables a curve to be plotted showing the relation between final reflux ratio and yield fraction, the R y curve, which is important to the plant designer. Such a curve was, in effect, proposed by Bogart (Z), who carried out a number of McCabe and Thiele constructions a t different reflux ratios, keeping the distillate composition constant, and plotted reflux ratio against composition of residue. He did not, however, allow for the effect of column holdup.
A
BINARY MIXTURES WITH COLUMN HOLDUP
The previous paper (8) showed that the moles of lighter component A held up in the column is equal to Q2,where Q = total moles of the mixture held up per theoretical plate, and L: = a i
+ az + a s . . . . . +
UN
It was further shown that in the special case where the reflux ratio is infinite, 2 can be calculated from up,N , and a. Consider a batch rectification under c.d. conditions in which the final reflux ratio is only moderately high, so that the yield of
distillate is substantially lower than when the final ratio is infinite. The column is assumed to be empty a t the beginning of the operation. If it is not, its contents must be added to the charge, and the quantity and composition of the latter modified accordingly. A McCabe and Thiele construction for the desired final reflua ratio gives the final bottoms composition a,; gives the sum of the final plate-to-plate liquid compositions, al f a2 a: uN = 2; and enables QS, the total column holdup of A , to be calculated. Taking material balances a t the end of the batch rectification:
+ . .... +
P + W = F -&N m Waw = Fat - QZ
+
whence
p,Fa/-‘W ap
- a,
: - N a W &- L a, - a,
Substituting y = Pap/Fu, and &/F = q gives the required yield: .Y=
apI(n/
- a,) - Q a, (a,
(2
- a,)
- Nu,)]
(1)
By carrying out a number of computations of a, for different reflux ratios and repeating the above calculations, the complete R y curve can be drawn, showing the variation of reflux ratio with yield fraction required to maintain a given distillate composition
