The study of 20 varieties of soybeans with respect to quantity and quality of oil, isolated protein, and nutritional value of the meal
Authors: Alderks O. H. 
Published: July 2007

Twenty samples of soybeans, representing the most promising strains now being grown at several stations were selected and prepared by J. L. Cartter and colleagues of the U. S. Regional Soybean Laboratory. Ten samples represented strains grown in the north central states and ten in the southern states. They were composited samples of the uniform soybean variety tests and therefore location and soil differences cancelled out, giving a good comparison of germ plasm.

Studies of these soybeans included the following:

Yield and quality of the oil with respect to flavor reversion.

Yield and quality of isolated protein for industrial usage.

Quantity and quality of protein for nutritional purposes as indicated by: a) Amino acid composition of solvent extracted raw and toasted flakes; b) availability of amino acids based on in‐vitro enzyme digestion tests.

The following is a summary of the results:

Samples analyzed for oil varied from 17.41% to 22.9% dry basis, equivalent to a difference of 98.8 lb. per ton of 10% moisture beans. Roanoke contained the highest per cent.

Samples analyzed for protein varied from 39% to 44%, dry basis, equivalent to a difference of 91.8 lb. per ton of 10% moisture beans.

Three strains grown at Lafayette, Ind., Ames, Ia., Urbana, Ill., and Columbus, O., varied as much as 1.79% oil and 3.1% protein, dry basis.

The fatty acid composition varied considerably. The triple unsaturated acids varied as follows: Per cent linolenic acid from 6.16% to 8.45% Per cent arachidonic acid from .01% to .09%. If these are important in the development of “flavor reversion,” one would expect no differences in the oils in this respect.

The quality and flavor stability of each solvent extracted oil from the 20 strains was top No. 1 grade. The oils were equal in flavor stability to the best quality commercial oils. All oils showed “flavor reversion” after aging in open new tin cans at 140°F. for several days.

The average yield of all 20 strains of alkali extracted, purified, isolated protein was 36.1% (DB). The yields varied widely from 33.1% to 42.7% (DB). Roanoke and Arksoy 2913 gave the highest yields of industrial protein.

No significant differences were found between the amounts of any one of the “essential” amino acids contained in the 20 soybean strains. There is no indication in this work that a strain might be selected and grown for the production of soybean meal with a superior protein. The “toasted” flakes contained less lysine than the hexane extracted, desolventized, raw flakes (average drop from 6.60% to 6.28%). There was no effect on the other “essential” amino acids.

In‐vitro enzyme digestion followed by microbiological assay was applied to methionine, lysine, and tryptophane. When the results are considered in the light of the accuracy of these new methods, it appears certain that there are no significant differences between the varieties in available tryptophane, but there is some possibility of significant differences in the availability of methionine and lysine.

This work was planned with J. L. Cartter of the U. S. Regional Soybean Laboratory and R. T. Milner of the Northern Regional Laboratory to determine whether the genetic composition of various soybean strains differed in regard to their ability to produce oil of good quality and whether the oils from these various strains might differ in flavor stability for any reason. Also we desired to determine if by agronomic selection and development of soybean varieties it would be possible to reduce the linolenic acid content in soybean oil.

Some investigators working on the soybean oil flavor reversion problem have attributed flavor reversion to result from oxidation products of the more unsaturated portion of the oil. It has been suggested also that various minor constituents in the oil possibly affected flavor stability by acting as catalysts to promote a certain type of oxidation. Cottonseed, peanut, sesame, and sunflower seed oils contain no linolenic or triple unsaturated fatty acids, and flavor reversion of the soybean oil type is not encountered with these oils. If linolenic acid could be eliminated from the composition of soybean oil perhaps the flavor reversion problem would be eliminated as well. In addition to quality of oil the strains of soybeans were examined for:

Quantity of oil in the soybeans.

Quantity and quality of pure proteins obtainable from the hexane extracted flakes suitable for industrial usage.

Quantity and quality of protein for nutritional purposes as indicated by: a) Amino acid composition of raw and toasted flakes; b) availability of amino acids based on in‐vitro enzyme digestion tests.

The 20 different strains of soybeans investigated in this work represented the most promising strains that are now being grown and investigated at the various stations.

Three strains (Lincoln, Richland, A‐4‐107‐12) were composites prepared by mixing equal quantities of seed from each of four locations in the corn belt (Lafayette, Ind., Urbana, Ill., Ames, Ia., and Columbus, O.) so that the resulting lots would reflect a general average of growing conditions and would give a good comparison between varieties. Seven other strains from the north central states and ten strains from the southern states were made up of carefully composited samples from the uniform soybean variety tests. The samples were prepared in this manner so that location and soil differences would cancel out as nearly as possible, thus giving a good comparison of germ plasm. A description of each strain obtained from J. L. Cartter is attached in the appendix.