June, 1922
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
delicate flavors: or aromas, that the slightest off-flavor in any of the ingredients becomes quickly noticeable in the finished beverage. All the sirups except Sirup 4 made equally satisfactory beverages, The slightly harsh sensation which had been given by Sirups 1 and 2 (inverted with acid) was not produced by the finished beverage. Lemon and ginger ale sodas made with Sirup 4 had a distinct off-flavor which ren-
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dered them inferior in quality to the other bottled sodas. The root beer made with Sirup 4 was much less affected, though it was considered somewhat inferior to the root beer made with ordinary sugar sirup and with the other invert sirups. Bottled sodas made with invert sirup were stored at room temperature over a period of two months of very warm weather. Their keeping quality was satisfactory.
A Study of Methods of Minimizing Shrinkage in Shell Eggs during Storage'" By L. H. A l ~ n y H. , ~ I. Macomber and J. S. Hepburn FOODRSSEARCR LABORATORY, BUREAUorr CHEMISTRY, U. S. DEPARTMENT OF AGRICULTURE, WASHINGTON, D. C.
The present study is preliminary to a general investigation of the cause and prevention of the development of cold storage odor and taste in eggs. It deals solely with the relative eficiencies of various sealing agents for preventing the escape of substances, mainly water vapor, from within the shell. Observations have been made of loss in weight of treated and untreated eggs kept at room or higher temperature for varying periods of time. Treatment with heated air for 5 min. fails to reduce shrinkage during storage. Immersion for short periods in heated or unheated aqueous solutions of mineral or organic acids, mineral salts, or soap fails to check shrinkage appreciably. Tests with drying, semidrying, and nondrying vegetable oils, nondrying animal oils, and mineral oils do not justify the conclusion that sealing properties can be definitely correlated with drying properties. Cottonseed oil apparently makes a very good sealing agent. The sealing ualue of mineral oi!s bears a definite relation to grade, as defined by gravity, flash point, and viscosity tests. Given equal sealing value, mineral oils should prove better than vegetable oils because they are less likely to impart odor and are less subject to change during storage. The addition of I or 2 per cent of soap to a mineral oil markedly increases its sealing value. Nothing is to be gained by the addition of gums, waxes. or rosin to relatively heavy mineral oils.
surrounding the yolk and the change in the consistency of the white. I n connection with a study of methods of preserving eggs by sealing the pores of the shell, Jones and DuBois6 made a thorough search through the literaturebearing on the general subject of egg preservation and report an extensive bibliography. As a result of their experiments they conclude that aluminium soap applied in a gasoline (or preferably a pentane) solution is an ideal substance for closing the pores of the shell. The method outlined is not a simple one, however. Several patented processes of treating eggs which have been developed within the last few years are being used commercially with apparent success. I n general, the processes consist in dipping the eggs into a hot bath of an oil or oil mixture for a few seconds and then usually into a similar cool bath. After drsiining, the eggs are packed in cases provided with well-made fillers and placed in storage. The treatment retards shrinkage during storage and as a rule the eggs bring a higher price than unprocessed storage eggs. It is claimed that treated eggs keep well, even at ordinary temperatures. Such an enhanced keeping quality is, of course, most desirable, especially in export shipments, as many ships have inadequate refrigeration facilities.
HE most noticeable of the changes which take place in eggs during cold storage are a loss in weight, the development of a characteristic odor and taste, a weakening
The present study was conducted as a preliminary to a general investigation of the causes and prevention of the development of the cold storage odor and taste in storage eggs. Rendering the shell membrane impervious to gases and vapors would provide a means for determining the extent to which the packing materials contribute to the characteristic taste. A membrane might be impermeable to water vapor, yet permit the passage of odorous volatile substances. This paper deals solely with the attempt to determine the relative efficiencies of various sealing agents for preventing the escape of substances, mainly water vapor, from within the shell. The treatments which are here found to be distinctly superior may be applied in the study of the related problem of preventing the entrance of foreign odors. Separate lots of eggs were subjected to the action of heated air and to immersion in aqueous solutions, in oils, and in oily mixtures. Observations were made of the losses in weight of these eggs and of untreated eggs held at room and higher temperatures for periods up to 35 days.
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of the membrane surrounding the yolk, and a change in the consistency of the white. Evaporation of water, which is an invariable accompaniment of the cold storage condition, accounts for practically all of the shrinkage observed. The second change may be due to absorption of odors and flavors from without, or t o the production of odorous substances within the shell membrane, or to both. The influence of foreign substances is facilitated by the natural porosity of the shell and the a f i i t y of the yolk for odors and flavors. Many in the trade believe that the so-called "cold storage taste" in eggs is due mainly to the absorption of odors from the egg cases, excelsior, and strawboard fillers and flats used in packing the eggs for storage. A small amount of experimental evidence' supports such an assumption, but adequate scientific data covering this point have not yet been presented. Enzyme action, which proceeds very slowly at the low temperature of storage, causes the weakening of the membrane 1
Received February 13, 1922.
* Published by permission of the Secretary of Agriculture. Food Research Chemist, Bureau of Chemistry. "Commercial Preservation of Eggs by Cold Storage," U. S. Dcgt. Agr.. Bull. 776 (1919). 33. 4
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HEATTRRATMENTS The air treatments (Table I) showed that heating of the surface for 5 sec. failed to reduce the shrinkage during stor5
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TABLEI-EFFECT
OF
HOTAIR TREATMENT O F EGGS After Storage for 35 Days a t Room Temperature-Comparative Loss in LOSS in Treated and UnWeight treated Eggs Per cent (Untreated= 100) 105.0 8.4 97.5 7.8 8.0 100.0
____ EGG^ Treated with air at 320' C. for 5 sec. Treated with air a t 610' C. for 5 sec. Untreated
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that the sealing properties are definitely correlated with the drying properties, although cottonseed and linseed oils, semidrying and drying, respectively, were more effective that the nondrying oils, neat's-foot and peanut. Cottonseed oil apparently makes a very good sealing agent, judging by the satisfactory results obtained with it in this experiment and in several others of a similar nature. TABLE111-EFFECT
6
age. In the remaining experiments eggs were treated by immersion for different periods of time in fluid media, either heated or unheated. The results of the heat treatments, though scant, suggest that the value in the use of elevated temperatures in the fluid immersion tests will lie in the action of the heat in facilitating penetration of the fluid into the pores of the shell rather than in any tendency to seal the pores by a hardening of the shell membranes or coagulation .of the proteins.
AQUEous SOLUTIONS Immersion of eggs for short intervals in heated and unheated aqueous solutions of mineral and organic acids, mineral salts, and soap, as shown in Table 11, failed to check shrinkage appreciably. The sulfuric acid treatment was by far the most effective, for, whereas the loss in the eggs treated with 5 per cent sulfuric acid solution was 26.4 per cent of that in the case of untreated eggs, the losses in those treated with the other solutions ranged from 66.4 to 106.4 per cent. Dilute solutions of sulfuric, orthophosphoric, and oxalic acids react with calcium carbonate to form difficultly soluble salts of calcium. The new salt forms a coating over the entire exposed surface of the carbonate, thus tending to stop the reaction. Apparently some such chemical action OCcurred in this experiment, as the acids mentioned produced a measurable effect upon the shrinkage of eggs thus treated. It is possible that the size and, to a smaller extent, the number of the pores were somewhat reduced by these precipitates. The slight beneficial effect of the aqueous solutions of the different salts employed in this test was due to mechanical plugging of the pores. The soap mixture6 was practically without effect upon shrinkage. A similar experiment in which cottonseed oil was used as the immersion fluid demonstrated that this oil is markedly superior to the aqueous solutions. The loss in eggs treated with the oil was but 4.5 per cent of that observed in the case of the untreated eggs.
OILS The value of an oil as a sealing agent may be expected to depend upon its viscosity, drying properties, odor, tendency to become rancid, etc. Eggs were treated with different oils representing drying, semidrying, and nondrying vegetable oils, .nondrying animal oils, and mineral oils. The data reported in Table I11 do not warrant the conclusion
* The soap used in this test and throughout the investigation was a variety of ordinary, moderate priced toilet soap, white, unscented, and lighter than water. TABLE11-EFFECT
IMMERSION FLUID Sulfuric acid 5 per c e n t , . Orthophosph'oric acid, 3.5 per c e n t . . Trisodium phosphate, satd. soln. Oxalic acid, 6.5 per c e n t . . Orthophosphoric acid, 3.5 per cent. Calcium acid phosphate, satd. soln.. Sodium aluminate, satd. soln.. Acetic acid, 6.0 per cent Acetic acid, 6 . 0 per c e n t . . Soap 6 0 per c e n t . . Dipdtassium phosphate, satd. soln Untreated.
..................... ........... ............... ..................... ............. ............ ................. ...................... ..................... ........................... .............. ...................................
OC.
25 25 100 25 50 97 100 25 40
98 100
...
DIFFERENT KINDSO F O I L S Comparative Loss in Treated and UnMethod of Weight treated Eggs IMMERSION FLUID Treatment' Per cent (Untreated = 100) At End of 5 Wks.' Storage at Room Ternfievatwe Cottonseed oil. I 0.5 6.3 I Linseed oil. 0.6 7.5 Neat's-foot oil. I 0.8 10.0 Peanut oil. I 1.0 12.5 Untreated. 8.0 100.0 At End of 12 Days' Storage at 40° C . Mineral oil A . I1 0.6 7.4 8.6 Mineral oil B . . I1 0.7 Mineral oil C . . I1 2.9 35.8 Mineral oil D I1 3.6 44.4 Untreated. 8.1 100.0 I In Method I the eggs were immersed for 5 sec. in the fluid a t 153: C cooled for a few seconds in a bath of the same fluid (33O C average), wipeb. gently with sterile gauze, and placed in a metal containe;.' In Method I1 the eggs were immersed for 7 sec. in the fluid a t 115O C then cooled for a few seconds in a bath ofthe same fluid (24' t o 30' C.),a d w e d t o drain without wiping, and placed in strawboard cartons.
10
10
300 60 10
10
..
IMMERSION O F
E G O S IN
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..
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..
MINERAL oms-The mineral oils employed in this experiment varied widely in efficiency. Mineral oil A had a specific gravity of 0.869, a flash point of 365' F., and a viscosity a t 100' F. of 134 (Saybolt units). Mineral oil D had a specific gravity of 0.851, a flash point of 255' F., and a viscosity at 100' F. of 44 (Saybolt units). . The other two mineral oils were intermediate in composition between A and D. The heavier oil (A) gave the best results. Equally good, and perhaps better, results might be obtained with slightly heavier oils. It is thus seen that the sealing value of these oils bears a definite relation to the grade as defined by the gravity, flash, and viscosity tests. From the experiments thus far recorded it is apparent that a mineral oil of the type represented by mineral oil A can b e used to advantage in sealing the pores of the shell of the egg. The vegetable and animal oils vary in their individual efficiency, but it seems possible to find an oil of this nature, such as cottonseed oil, which will give results comparable with those obtained with the better mineral oils. If these oils imparted an odor to the surface of the eggs, as some of them might, their use would be objectionable. Furthermore, they are more subject to change during storage than the mineral oils. I n general, therefore, of the different kinds of oils of equal sealing value the mineral oils would prove the most satisfactory. Attempts were made to increase the efficiency of the mineral oils by the addition of substances with which they are miscible. By adding about 1 or 2 per cent of soap to the four mineral oils listed in Table 111it was found possible to] increase their sealing properties markedly. The addition, of 1 g. of soap to 100 cc. of mineral oils A, B, and D lowered the loss in treated eggs from 7.4, 8.6, and 44.4 per cent of
Duration of Immersion Sec. 300 300 10 300 60
OF
Loss in
OF IMMERSION OF
Temperature of Fluid
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EGGSIN AQUEOUS SOLUTIONS
Loss in Weight dur- Comparative Loss in,
ing Storage for 18 Days at 40' C. METHOD OF COOLING EGGS Grams Per cent In air 1.64 2.9 In air 4.16 7.3 I n immersion fluid a t 30° C. 4 . 1 1 7.3 In air 4.49 8.4 In air 5.00 9.5 In immersion fluid a t 30' C. 5 . 6 7 9.5 In immersion fluid a t 30° C . 5 . 8 6 9.6 In air 6.74 9.9 In air 6.01 10.1 In air 6.56 10.7 In immersion fluid a t 30° C. 6 . 4 9 11.7 6.04 11.0
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Treated and Untreated Eggs (Untreated = 100) 26.4 66.4 66.4 76.4 86.4 86.4 87.3 90.0 91.8 97.3 106.4 100.02
