620
INDUSTRIAL 24ND ENGINEERING CHEAMISTRY
Concentrations of 1.0, 2.0, and 2.75 per cent to the stock (1.8, 3.6, and 5.1 per cent to the rubber, respectively) were used. From Figure 7 it is seen that more than 3.6 per cent to the rubber was necessary to give complete protection for one week. The price of this material, together with its tendency to bloom and discolor fabric32and other materials with which it comes in contact, make this specific antioxidant of doubtful commercial interest in the control of sun-checking. Conclusions
Through the proper selection of rubber, reclaim, and compounding ingredients, it is possible to reduce to a marked extent the tehdency for rubber products to crack and check. The maximum results from a checking standpoint would Weber, J. SOC.Chem. I n d . . 19, 546 (1900).
Vol. 18, No. 6
be obtained by using, in rubber compounding, only those materials that are protective in their action, but, unfortunately, selective pigmentation cannot usually be resorted to, without the sacrifice of desirable physical properties. Gas black, for example, has no protective action, and, even in small quantities, offsets the protective influence of other pigments, but for stocks such as tread stocks this pigment is highly desirable from the standpoint of toughness, resistance to tear, and abrasion. Other characteristics, such as the blooming of certain of these protective materials, make their commercial application very difficult. However, in spite of these disadvantages, and in spite of certain limitations imposed by physical properties, much can be done to improve the weathering of all types of rubber compounds, and in some cases i t is even possible to make them completely resistant for long periods of time.
Milk Powders as Food' 11-Observations on the Existence of Vitamin E By L. T. hnderegg and V. E. Nelson IOWASTATE COLLEGE, Aarss, IOWA
There is a marked difference in the nutritive value of REVIOUSLY reported entirely different. The data whole and skimmed milk powders aside from the fat observations2J on the for Lots 1 and 2, on Diets content. Additional observations are recorded which nutritive value of milk 1 and 2, as indicated in the must be taken into consideration in connection with powders indicated that when respective tables, illustrate the existence of vitamin E. When cod-liver oil is ini r o n c i t r a t e was added to this point. Also, on a diet corporated in skimmed milk powder diets, as a source whole milk powder the diet of skimmed milk powder 60.0, of fat-soluble vitamins, it undergoes decomposition b e c a m e a d e q u a t e for the iron citrate 0.2, agar-agar 4, giving rise to products strongly suggestive of acrolein. g r o w t h , reproduction, and butter fat 5.0 (or cod-liver Other highly desiccated materials also induce this rearing of the young of the oil 5.0), and dextrin to 100, decomposition. Addition of ethyl alcohol, wheat oil, rat. It was further shown rats grew normally, but there or water to such mixtures exerts a protective action. that the relative amount of was no evidence of reproducSkimmed milk powder diets, upon which rats are sterprotein, fat, and salts is of tion. (Diets 3 and 6, Table ile, were so changed by the addition of water and adgreat importance, and that I, and Lots 6 and 16, Table ministering the cod-liver oil separately that fourth reproduction may be greatly 11.) Although skimmed milk generation young have now been obtained. influenced by the amount of powder diets containing 5 per These results indicate that some of the conclusions cent of filtered butter fat as iron salt added. It was conpreviously drawn relative to the existence of vitamin E the sole source of fat-soluble cluded that the whole milk are now no longer tenable. The mere addition of water vitamins were unfavorable powder employed was adeto a highly desiccated diet may markedly influence its for reproduction, the addiquate as concerns the protein nutritive value. tion of 5 per cent of filtered and vitamins necessary for butter fat to an oats diet g r o w t h , reproduction, and the rearing of the young of the rat. Other'observers have as the only source of added vitamins A and D supplied since reported succeis with reproduction on whole milk pow- sufficient of these chemical complexes so that rats c0;l-d be reared to the fourth generation. The oats diet had the folder diet^.^,^^^ During this work a marked difference was observed between lowing composition: oat groats 93 per cent, sodium chloride the nutritive value of whole milk powder and skimmed milk 1 per cent, calcium carbonate 1 per cent, and filtered butter powder. This difference cannot be attributed solely to a fat 5 per cent. It appears that 5 per cent of butter fat supdifference in the fat content, for when skimmed milk powder plies a sufficiency of these vitamins for growth, reproduction, was suitably supplemented so that the resulting diet con- and rearing of young. formed in chemical composition to one of whole milk powder, Table I-Percentage Composition of Milk Powder Diets on which very good results concerning reproduction were Whole Skimmed Iron Salt Cod- Wheal milk milk cit- Agar- Dex- mix- Ca- Butter liver embryo Harris obthined, the outcome on the skimmed milk powder diet was Diet powder powder rate agar trin ture sein fat oil oil yeast
P
r
1 Reported a t the Intersectional Meeting of the American Chemical Society at Iowa City and before the joint session of the Divisions of Agricultural and Food Chemistry and Biological Chemistry at the 70th Meeting of the American Chemical Society, Los Angeles, Calif., August 3 to 8 , 1925. 2 Anderegg, J . Biol. Chem., 69, 587 (1924). 8 Anderegg and Nelson, THIS JOURNAL, 17, 451 (1925). 4 Matill, Carman, and Clayton, J . Biol. Chem., 61, 729 (1924). 6 Maze, Comfit. rend., 160, 1683 (1926);C. A , , 19, 2693 (1926). 6 Woods, J . B i d . Chem., 66, 57 (1925).
1 2 3 4 5 6
60.0 65.0 60.0 50.0 50.0 00.0
0.2 0.2 0.2 0.2 0.2 0.2
4.0 4.0 2.0 2.0 2.0 2.0
27.4 2.4 6.0 13.8 1.0 16.0 32.8 5.0 38.8 2.0 47.8 32.8 5.0
5.0
2.0
Evidently, these observations show that further investi'gations on the nutritive value of skimmed milk powder might lead to interesting and useful results, both from a practical
INDUSTRIAL AND ENGINEERING CHEMISTRY
June, 1926
Table 11-Growth, Lot
Diet
11
5
Generation 1 1 1 1 1 1 1 1 2 1 1
12
5
1
2
13
5
1
3
3
14
6
2
4
5
15 16
5
3 1
3 3
7
6
Males 2 3 2 2 2 2 2 2
Females 5 5 3 3 4
2 2 2
3 3 4
4
4 4 3
5
621
Reproduction, a n d Rearing of Young o n Powdered Milk Diets Young Young Growth Litters born weaned REMARKS 17 N 139 132 8 N 32 7 Only 1 litter reared 4 N 26 15 Whole liquid milk in diet 2 N 12 7 Cream in diet 3 N 19 9 Orange juice in diet 0 0 0 No addition 4 28 20 3 5 21 N 2.0 uncertified cod-liver oil and 2 yeast separa :ly 0 N 0 0 2.0 uncertified cod-liver oil and 2 yeast separa ?ly 1 2 . 0 uncertified cod-liver oil separately, no yea N 0 0 Basal ration wetted and then dried 7 N 4 5 7.0 uncertified cod-liver oil and 2.0 yeast added Basal ration wetted and then dried N 4 13 10 2.0 uncertified cold-liver oil and 2.0 yeast added 5 . 0 water incorporated 37 N+ 6 33 2.0 certified cod-liver oil and 2.0 yeast separately 5 . 0 water incorporated N+ 10 54 37 2.0 certified cod-liver oil and 2.0 yeast added 5 . 0 water incorporated N+ 7 46 2.0 certified cod-liver oil and 2.0 yeast added N 0 0 0
”+
I
and from a theoretical viewpoint. The value of such information to the producers and consumers of these products is sufficiently obvious. Previously, butter fat had served chiefly as the source of the fat-soluble vitamins. I n the experiments to be considered a t this time cod-liver oil was also employed to furnish these substances. Since the results concerning reproduction were decidedly abnormal when skimmed milk powder was supplemented with butter fat and iron salts, it was suggested that possibly some change had occurred in the butter fat. The nutritive value of the fat as i t occurs in whole milk might be different from the filtered butter fat as i t was employed in making up the diets. If such a change took place it might account for the differences in nutritive value between whole milk powder diets and similarly composed skimmed milk powder diets. Such a change could be due to the destruction or the removal of a necessary dietary principle. It is also possible that the difference might be due to a dietary factor other than vitamins A, B, C, and Dnamely, a vitamin having to do specifically with reproduction, and which is present in whole milk powder but not in skimmed milk powder.
prepared in quantities of a kilogram, and are then stored in 2-quart mason jars. Under these conditions some of the material may remain unconsumed for a period of 10 days if the number of rats fed thereon is small. Under such conditions, when cod-liver oil was a component of the diet, very pungent and penetrating odors strongly suggestive of acrolein were produced. However, when wheat embryo oil had also been added to such a diet no such decomposition was observed. On such diets, when wheat embryo oil was incorporated, reproduction and rearing of young occurred. Lot 7 on Diet 4 illustrates this statement. The efficiency of wheat embryo oil in inducing reproduction has been pointed out by Evans’ and also by Sure.* Among their experiments Evans and Bishop9 included in one of their diets cod-liver oil to the extent of 24 per cent and, since reproduction was not augmented, concluded that this oil did not contain the reproductive vitamin which has recently been designated vitamin E by Sure,”Jand Evans and Burr.” Evans and Bishops also employed yeast to the extent of 25 per cent of the ration. I n summarizing their findings they say, “Whole milk, fresh or dried, cod-liver oil, orange juice, and yeast fail to act as curative agents when added to the basic diet.” Evans and Effect of Addition of Certain Substances on Nutritive Burr” state that “whole milk powder may constitute one-third of the ration by weight and sterility result.” The writers have Value of Skimmed Milk Powder previousIy shown that reproduction occurred on a synthetic If the nutritive value of the butter fat was impaired by the diet when all the vitamins were furnished by whole mills various treatments it received, positive results might ob- powder present to the extent of 15 and 30 per cent by weight tain if liquid whole milk, or cream, were added as a further of the diet. The first of these diets contained about 4.1 supplement. Orange juice was also tried, as it is a potent per cent of butter fat while the second contained about 8.3 source of certain vitamins. Diet 3 was employed in these per cent. Both of these diets, on which reproduction and experiments. The feed containers were about half filled rearing of young occurred, contain smaller amounts of butter with the dry mixture, after which enough of the liquid sup- fat than the basal ration of Evans and BishopJgwhich contains plement-whole milk, cream, or orange juice-was added so 9 per cent of butter fat. The basal ration of Evans and that the thoroughly stirred mixture became a thin paste. Bishop9 also contains 15 per cent of lard, whereas no lard Positive results were obtained (Lots 3, 4,and 5 , in Table 11), was used in the diets containing 15 and 30 per cent of whole while no reproduction was obtained with Lot 6, which was milk powder mentioned above. on the experiment a t the same time and under the same genThe writers have made some very limited observations eral environmental conditions as Lots 3, 4, and 5 . This employing practically the basal ration of Evans and Bishopggroup served as a control. Reproduction has never been namely, casein 18, dextrin 54, lard 15, butter fat 9, salts 4. observed on this diet (Diet 3), although a large number of Four lots of animals were kept under similar environmental animals have been employed. From the observations on the conditions and observed for about 4 months. I n addition oat diets it appears that a sufficiency of fat-soluble vitamins to the basal diet one lot received yeast only, the second yeast is present in Diet 3. The results of these four experiments and butter added separately, the third yeast and cod-liver indicate that the liquid supplement, whether whole milk, oil separately, and the fourth yeast and wheat embryo oil cream, or orange juice, exerted a beneficial action when in- separately. There was no evidence of pregnancy among the corporated in the skimmed milk powder diet. On the females of any of these lots of animals. skimmed milk powder diet alone without supplement results Surelo also failed to get reproduction on skimmed milk on reproduction and rearing of young were negative. powder diets supplemented with 2 per cent of cod-liver Effect of Certain Diets on Added Cod-Liver Oil
When cod-liver oil was added to supply the fat-soluble vitamins in earlier experiments, a peculiar and characteristic decomposition was observed. The diets are usually
Science, 80, 20 (1924). Bioi. Chem.. 84, 371 (1924). 9 J . Met. Res., 8,233 (1923). 10 J . Bioi. Chem., 18, 893 (1924). 11 Proc. Nul. A c a d . Sci., 1, 336 (1925). 7
* J.
622
I-VDUSTRZAL A 9 D EiVGI;\iEERI.YC; CHEMISTRY
oil. Addition of various extracts of wheat embryo, yellow corn, and several other substances gave positive results, and Surelo interpreted these findings to prove the existence of a vitamin specific for reproduction which he named “vitamin E.” Decomposition of Cod-Liver Oil
Cod-liver oil was mixed with a number of dry substances in order to determine whether similar decomposition would occur. Stoppered wide-mouth bottles of about 800-cc. capacity or quart mason jars were used as containers. To 200 grams of material 5 per cent of cod-liver oil was added and the whole thoroughly mixed and placed in the glass container, which was then tightly closed. Whole milk powder, skimmed milk powder, starch, and finely ground dextrin were tried and induced similar decompositions of the added oil. The addition of anhydrous ether, chloroform or benzene to thk extent of 5 per cent did not prevent the decomposition, while such substances as 95 per cent alcohol, wheat embryo oil, and water exerted a protective action increasing in the order given. Moreover, the protection due to the water varied with the quantity added. With 10 per cent of added water no decomposition of the oil was evident even after several months. Mustiness and discoloration ensued, but the odor so characteristic of the other decompositions could not be discerned. The 5 per cent of added wheat embryo oil prevented noticeable decomposition for about a month. Although decomposition was noticeable with whole milk powder, the amount and rate of decomposition was markedly less than with skimmed milk powder. I n the light of these observations it appeared that the lack of successful reproduction on skimmed milk powder diets might be attributed t o the action of the highly desiccated material upon the added fats. Should this theory be well founded, then better results might obtain if the fats were fed separately, or if the diet were moistened before adding the fat. Effect of Moistened Diets and Feeding the Fat Separately
All experiments described were made with rats of an initial weight of 50 to 60 grams, selected from the breeding colony, which consists of a very healthy, vigorous qtock of animals. Two brands of cod-liver oil purchased locally were employed. The yeast was obtained from the Harris Laboratories. Dextrin was prepared by autoclaving cornstarch moistened with a 1 per cent citric acid solution a t 1 atmosphere (15 pounds) pressure for about 3 hours, with subsequent drying over steam coils and then grinding to a moderately fine powder. The skimmed milk powder was obtained from the Merrell-Soule Co., Syracuse, N. Y. The animals were kept under as nearly identical environmental conditions as possible and were observed daily. I n order to reduce the labor involved, a basal diet of skimmed milk powder 50.0, agar-agar 2.0, iron citrate 0.2, and dextrin 47.8 was prepared. Added cod-liver oil, yeast, or water was then calculated to this mixture as a basis. Lots 8 and 9 received this basal diet, Diet 5, with 2 per cent of uncertsed cod-liver oil and 2 per cent of yeast fed separately. The yeast and oil were mixed with a little water and placed in a petri dish. These portions were readily consumed by the animals. On this diet, the first generation, Lot 8, grew normally, reproduced, and reared young. The second generation, Lot 9, though under observation for 9 months haa not reproduced. Lot 10 received a similar diet save that the yeast was omitted. Although growth was comparable in these experiments, only one female of Lot 10 was obviously pregnant. She died before the young were born; autopsy revealed 6 fetuses. Altogether, the results on these diets were not very satisfactory.
1’01. 18, No. 6
On the supposition that the physical condition of the milk powder might have some influence on its nutritive value, the basal ration was treated with water until a thin paste was formed. This was dried, coarsely ground, and the cod-liver oil and yeast added to the ground material. Lot 11 received this diet, containing 7.0 per cent of added uncertified codliver oil and 2.0 per cent of yeast. Lot 12 received a similar diet, except that the added oil was reduced to 2.0 per cent. Each female of both groups became pregnant. I n Lot 11 two females died a t parturition and two gave birth to young. Of these latter one consumed the young before they could be counted, while the other reared 3 of her 7 young. Quite similarly, two females of Lot 12 died a t parturition, the two remaining ones gave birth to litters of 5 and 8, of which 2 and 8 were reared. The young were inferior a t weaning. I n Table I1 all litters are indicated, but the number of young refers only to those actually born. I n these experiments the decomposition of the added cod-liver oil was not entirely averted. It is now believed that this was because the material was too thoroughly dried after having been wetted. The odors characteristic of the decompositions described above were noticed several times. The best results so far obtained on skimmed milk powder diets are illustrated by Lots 13, 14, and 13. The dextrin, agar-agar, and iron citrate were mixed, 5 per cent water incorporated, after which the milk powder was thoroughly mixed into the moistened mass. More than 5 per cent of added water makes the mixed mass too sticky to handle easily. Certified cod-liver oil to the extent of 2 per cent and yeast 2 per cent were fed separately. It so happened that one of the three females of Lot 13, the first generation, was sterile throughout. The other two females each gave birth to three litters of young. Of 37 young born 33 were reared. The second generation, Lot 14, likewise grew normally. The females reproduced and reared young. Of 54 third generation young born 37 were weaned. The females of Lot 15, third generation, have just had their first litters. I n all, 7 females of this lot have had young which constitute the fourth generation. The total number of fourth generation young mas 46. From the appearance of the young there is every reason to believe that they will be weaned and grow nmmally. Reproduction and rearing of young are occurring on a diet which has hitherto been considered inadequate in this respect, on a diet, in fact, which has been employed to adduce proof for the existence of a vitamin specific for reproduction. It is now believed that a highly desiccated diet may have a very deleterious action on some of the added components. The mechanism of the destructive action, while under investigation, is not understood, It is now further believed that some of the conclusions previously drawn from observations of the reproduction of rats on skimmed milk powder diets, with reference to the existence of a vitamin specific for reproduction, are no longer tenable. Further, the simple expedient of adding water to certain highly desiccated diets, which, as such, are unsatisfactory because of lessened palatability and because of destruction of certain components, may greatly improve their nutritive value. Acknowledgment
The writers desire to thank the Merrell-Soule Company for supplying some of the materials used in this investigation.
Willard Gibbs Medal Award The Willard Gibbs Medal has been awarded to Sir James C. Irvine, of The University of St. Andrews, Scotland. The medal will be presented to him a t the meeting of the Chicago Section which will be held on Friday evening, September 17, 1926. Dr. W. Lee Lewis is in charge of the committee planning the award and will present the medal.
.
