INDUSTRIAL ALVDEiVGIXEERIiVG CHEAMISTRY
498
Vol. 17, No. 5
Production and Nutritional Value of Commercial Wheat Germ Extract’ By Charles Hoffman WARDBAKING Co., K s w YORK.N. Y .
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H E A T berries are made up of approximately 83.5per cent e n d o s p e r m containing the greater part of the starch, 15 per cent bran constituting the outer seed coats, and 1.5 per cent germ containing the embryo of a new plant. In spite of the small amount of germ present it contains a large portion of the vitamin B of the wheat berry and some very valuable proteins. It is with these constituents of the germ and their partial isolation on a commercial scale that the present paper deals. Composition of Wheat Germ
Commercial wheat germ (moisture-free) was found by Osborne and Mende12to have the following composition: Per cent 7.71
Starch Pentosans, etc. Protein (hT X 6.25)
7.50 18.21 8.29 31.00
Fiber Fat Ash Undetermined
Per cent 2.35 10.44 4 91 5.59
The material with which they worked and upon which this analysis is based was found to contain approximately 23.5 per cent endosperm, 23.7 per cent bran, and 52.8 per cent pure wheat germ. Frankfurt3 made a careful investigation of the wheat embryo and reports the following analysis of the pure germ: Per cent Carbohydrates soluble in water including sucrose and raffinose (6 89%) 24.34 “Crude protein” [N(6 44%) 4 0.25 X 6251 Fiber 1.71
in papers by hIcCollum, Simmonds, and pit^,^,^ by Bell and Mendel,’ by Voegtlin, Lake, and Myers,8 by Osborne and h!iendel,2 by McC ~ l l u m ,and ~ by Chick, Hume, and C ~ o p e r . These ~ discussions cover the subject thoroughly and show the great value of wheat germ as a source of this indispensable vitamin. In spite of these valuable qualities the germ of the wheat has only recently been utilized for human food by the addition of a prepared extract to white bread,”J and the pronounced tendency to rancidity possessed by the germ has prevented its extensive use as animal fodder.
Wheat germ, a by-product of the flour mills, has been converted into an extract that may be used for human nutrition. The valuable properties of the germ-its high vitamin B content, its proteins of high nutritional value, and its content of the unidentified factor X, necessary for reproduction-have been preserved in the extract. The preparation of this extract has been briefly reviewed and feeding experiments conducted to show its valuable properties have been described. The toxic properties of the oil of wheat germ have been confirmed, and extensive biological experiments have shown that the removal of this oil results in a product more nutritious than the original germ. The high nutritive value of the proteins contained in the wheat germ extract has been shown by further feeding tests, Charts of growth curves of test animals under various conditions are given, as well as the analysis of the extract. Attention has been called to the value of the extract of wheat germ in food for infants and invalids.
Per cent 13 51
Crude fat Ash Undetermined (chiefly insoluble carbohydrates)
4 82 15 37
Complete discussions of wheat embryo and of the nutritional value of its proteins have been published by Osborne and Mendel,2 McCollum,4 and by McCollum, Simmonds, and pit^.^ Briefly summarized, the results of these investigators tend to show that the proteins existing in the germ of wheat are of very high nutritional value compared with the proteins of milk and eggs, and are apparently much more nutritive than those contained in the other parts of the wheat berry. This high nutritional value of the germ is further enhanced by the fact that it contailis a very large proportion of the vitamin B content of the whole berry. Discussions of the vitamin distribution in the whole berry and of the character of the vitamin present are found Received August 6, 1924 J . Baol. Chem., 87, 557 (1919). 3 Landw. Vers.-Sta., 47, 449 (1896) “The Newer Knowledge of Nutrition,” 2nd ed Macmillan Company. 8 J . Biol. C h e m , 26, 108 (1916).
General Considerations
From the wealth of discussion of the valuable properties of its proteins, its vitamin B content, and its desirable mineral constituents, and from the fact that it was not being utilized for these valuable properties, the idea of preparing from the germ of wheat a usable product in the form of an extract wai worked out. As a result a loaf of white bread was prepared which contained all the elements necessary for a complete diet, as has been described in articles a l r e a d y cited.I0 Later it was decided to investigate in greater deCe.’’s tail the properties of this wheat germ extract with a view to comparing it with the results obtained by other investigators on wheat germ itself and with the idea that its properties might make it extremely valuable for other uses besides in bread. The results of careful investigation fully j u s t i f i e d these expectations. Figure 1-Longitudinal Section t h r o u g h a Grain of Wheat The commercial production S h o w i n g the M a i n C o m p o n e n t of such an extract as would Parts (after Jago) contain the valuable constituents of the original germ unimpaired presented many unexpected problems of engineering and manipulation, but these have been successfully solved and commercial production of the product is-now a reality.
1
J . B i d . Chem. 28, 1916 (1916). A m . J . Phrsiol., 62, 145 (1922). Public Healfh Refit. 83, 647 (1918). 0 Med. Research Cam. London, Sfiec. Refit. 38. 10 Hale, THIS JOURNAL, lS, 122 (1923); Ho5man, Ibid., lS, 1225 (1923). e
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7
, 1922, p.
124 The
I S D C S T R I A L A S D E N G I S E E R I S G CHEMISTRY
May, 1925
Commercial Problems
Few flour mills were separating the germ from the shorts (feed) at the time these in\-estigations Tvere started, and those that made any kind of a separation made a very incomD / € TS
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than those on the original. This difference became more pronounced in longer tests than that shown in the figure. Certainly this proved that the value of the germ was not being injured by the treatment, but that it was actually being improved. The crude oil obtained from the extraction of the germ in commercial manufacture is h e a q and very dark brown in color. I t has a pronounced bitter, astringent taste which is cliaiacteristic of this oil. I t has unusual emulsifying propertie; wid froths easily with agitation. Toxicity of Wheat Germ Oil
iizlEEK Figure 2-Growth Curves Showing T h a t Commercial Extraction of Oil f r o m Wheat G e r m Does Not Injure n o r R e m o v e Any of Vital E l e m e n t s of G e r m
plete one. The best product obtainable a t that time was a mixture containing mostly bran and endosperm with a small proportion of germ. It was therefore necessary to interest the millers in separating the germ completely from other products so that the raw material for extraction would contain a minimum proportion of unnecessary bran and endosperm. -1satisfactory germ was finally obtained. The commercial germ contains about 10 per cent of an oil which has a bitter, disagreeable taste and odor and is not very stable. This oil interfered with the extraction of the valuable water-soluble constituents, and the commercial success of the extraction processes is largely attributed to the removal of the oil. It can be extracted commercially from the germ by benzene or carbon tetrachloride, and tests made both in this laboratory and others show that none of the valuable ronstituents of the germ are removed by either solvent, High temperatures and comparatively long periods of time were necessary to complete the extraction, and it was feared these might damage the nutrient constituents that were to be removed later. Vitamin B is particularly susceptible to temperature, and consequently feeding experiments were designed and carried out to determine the effect of the operation on this constituent. Test animals were fed a diet I
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