Uses of Soybean Protein in Industry

Allan K. Smith.

Soybeans are easily processed for oil and meal. They are formed into flakes more easily than other oilseeds an unusual property that has given them a strong advantage in solvent-extraction operations. Furthermore, its high nutritional value and great abundance have placed the protein first among the protein concentrates used for animal feeds. Likewise, soybean oil is used in greater tonnage than any other vegetable oil in production of hydrogenated shortening, and its semidrying and other properties adapt it to many industrial uses.

Ahead of the industrial uses of soybean protein, of course, must come its use as feed. The tonnage of soybean protein used industrially is small compared to that used for stock feed: it is estimated that little more than 5 percent of the processed soybean meal finds it way into industrial products. Likewise, the consumption of soybeans for human food in the United States is comparatively small, roughly comparable to the industrial consumption. During the war and the postwar period, soybean flour was shipped to our Allies in rather substantial quantities. While the industrial and food uses of soybean protein are increasing, soybean production has increased at an even faster pace. At the beginning of the Second World War, production doubled, from 100 million to 200 million bushels in a year, and the 1950 crop was estimated at 270 million bushels. Some people are forecasting still larger production for the future.

Industrial utilization of soybean protein covers a broad variety of products. The term "industrial protein" applied to soybeans designates products ranging from crude oil meal (44 percent protein), used in stock feed and in some industrial products, to isolated and refined soybean protein (100 percent protein) and the products derived from the protein.

Each grade finds utilization in keeping with its properties and cost. New uses appear regularly. Soybeans, because of their relatively low cost of production, are an exceptional farm crop for scientific and technical development. The price of a product is always a factor in its success; hence the low cost of the oil and protein gives soybeans an advantage over similar products from other oilseed crops for industrial markets.

Proteins have assumed industrial importance only in comparatively recent years. The slow development may be attributed to their great importance for foods (restricting the available supply for industrial application) and the exceedingly difficult chemistry of the protein molecule. Of all natural products, the proteins present the most complicated puzzle with which science has to deal.

The fundamental problem of protein supply in the United States, however, has changed from one of scarcity to one of plenty, mainly because of the introduction of the soybean. In evaluating what lies ahead for soy protein, we shall consider the utilization of the soybean meal and the isolated protein. Under isolated protein we shall discuss the problem of whey disposal and its influence on locating protein refining plants, and the competition, characteristics, and applications of the proteins.

Dehulled soybean oil-free meal contains about 50 percent protein. It is a raw material for making isolated protein and has several other important industrial applications. It makes an excellent glue that has good water resistance.

The use of soybean-meal glue in fabricating plywood from both hard and soft woods in peak years has reached 45 million pounds. Another well-established and substantial use of the glue is for wallpaper coating. During the war, soybean meal was used in conjunction with casein or isolated soybean protein for brush-coating paper. The results were so satisfactory that this use appears to have been adopted permanently by the paper industry.

Because of the low cost of soybean meal and its good adhesive strength and water resistance, other substantial uses can be expected. The development of tacky adhesives from soybean meal would greatly extend its usefulness in fiberboard construction and in packaging. The paper industry offers many opportunities, especially in the fabrication of high-quality paper boxes, which equal or surpass similar boxes of wood construction. The fulfillment of such applications would require substantial quantities of soybean meal.

THE PROTEIN ISOLATED or extracted by chemical means from undenatured (no heat treatment), solvent- extracted soybean flakes is a highly specialized product with the general name of soybean protein.

Attention to details is necessary to produce a standard product. The process consists of dissolving the protein in the undenatured hexane-extracted flakes with dilute sodium hydroxide and removing the insoluble part of the meal by screening and centrifuging. The protein is precipitated from the solution by adding acid to a pH value of 4.6 to 4.0; the precipitated curd is filtered and dried. Some processors bleach the protein and give it a mild hydrolytic treatment to develop desirable properties. Although the protein is easily prepared in a purified state in the laboratory, the operation of a large-scale plant has many engineering problems.

There also occurs in this process a serious problem of waste disposal.

In the production of isolated protein, two other fractions are obtained. One is a solid residue with a relatively high percentage of unextracted protein. It may be used in feed mixtures or for extending phenolic resin glues and plastics.

The other comes out in a dilute water solution; about one-third of the original meal appears in it. For convenience it is called whey. It contains proteins and sugars which, if recovered, could be used as feed, but evaporation is the only method now available for such recovery, and that is not economically feasible.

Disposal of the whey as sewage is restricted in many localities where authorities are trying to prevent pollution of lakes and rivers. The large rivers, such as the Mississippi, Missouri, and Ohio, however, may be open indefinitely to sewage disposal. Apparently then the waste-disposal problem restricts the location of the factory. A sewage-treatment plant is presently the only other acceptable method for whey disposal. Future research may find a more economical and practical procedure, such as using it as a nutrient for growing yeast.

A NEW PRODUCT from soybeans now coming on the market has been named Gelsoy. It is a result of a series of investigations at the Northern Regional Research Laboratory by A. C. Beckel, Paul A. Belter, Mrs. Letta DeVoss, and me on the use of alcohol (ethanol) as an oil solvent. We found that extracting soybeans with alcohol improved the color and taste of the meal and the protein isolated from it and that the alcohol either removed an antigelling factor or converted the protein into a more readily gelable form.