PROTEINS ARE BASIC

Over-all Look at Industrial Proteins

Allan K. Smith.

The proteins for industry come from both animal and vegetable sources. When they are derived from the animal-processing industries, we call them byproducts. When they come from vegetable sources, we call them primary products.

The most important industrial uses of proteins are in making adhesives or glues. From them also are made buttons, sizing for both paper and textiles, fibers, medicines, pharmaceuticals, and many other items.

The type of proteins that can be used industrially is limited. We think of proteins first as food and feed. But recently the potential supply of vegetable and animal proteins in the United States has greatly increased, largely because of the greater efficiency of crop production through mechanized farming and the introduction of the soybean. I have no reason to believe that we have reached maximum production. The need for extra food during the Second Word War caused a temporary shortage of proteins in this country, but at the same time it greatly stimulated agricultural production.

The use of vegetable proteins by industry has a great economic advantage over the use of animal proteins, because an animal uses 6 to 10 pounds of vegetable protein to produce 1 pound of animal protein. That economic relationship limits the use of animal proteins to byproducts of meat packing, fishing, and dairy industries.

Not all proteins are fit for food for example, fish residues and bones and hides from the packing and tanning houses, which are a source of isolated protein. On the other hand, casein, which is derived from milk, is used preferably in dairy products such as fluid milk and cheese, and only temporary surpluses go into the making of casein. Edible gelatin brings a higher price than gelatin that is to be made into glue. Furthermore, the waste and leftovers of an industry are naturally in limited supply and cannot be given primary consideration as a source material of expanding usefulness.

The cheapest and most abundant supply of primary proteins is found in our vegetable crops cottonseed, flax, soybeans, peanuts, wheat, and corn. The proteinaceous materials derived from the processing of oilseeds for their oil and cereal grains for starch provide a large and cheap source of crude materials for producing isolated vegetable proteins for industry.

Wool, silk, hair, and hides are important proteins, but I shall not discuss them here because they are used largely in their original form.

In considering the proteins as industrial raw materials, therefore, one has to look at them in the light of the abundance of the materials from which they are prepared, their cost in comparison with the costs of competitive materials, their present uses, and the possibility of developing new products from them. The wartime disturbance of economic conditions and the changing world situation prevent an accurate evaluation of some of those factors, but we can indicate the general trends.

The industrial proteins of animal origin include the packing-house byproducts usually known by the names of animal glue, photographic gelatin, edible gelatin, blood albumin, fish glues, egg albumin, and casein.

The industrial vegetable-type proteins derived from farm crops appeared on the market after the First World War. The first industrial use of soybean meal as a glue was in a plywood mill in the State of Washington in 1922;. isolated soybean protein appeared in 1933; and the corn protein, zein, in 1938.

PROTEINS SUPPLY only some of the adhesive materials. Starch and dextrin adhesives are cheaper and are used in larger volume than glues from protein. The synthetic resins appeared on the market in plywood glue about 1936 and are now used in large amounts, notably for waterproof plywood. Natural gums and rubber adhesives are special types. Resistance to water is an important requirement for many adhesive applications. Starch and dextrins have little or no resistance to the dissolving action of water. Properly formulated protein adhesives are highly water-resistant. Many of the synthetics are classified as waterproof.

We need thousands of different formulas for glue because glues have so many different uses. The preparation of the formulas is largely an art. It is based more on an operator's experience than on chemical or scientific knowledge of what makes a glue stick. Glues literally hold the world together : Your wallpaper would fall from the wail and your chair and many parts of your house would come apart if the glue in them were to change to sand.

The gelatin-type glues were used by the early Egyptians. The first glue plant in the United States was established about 1808. We have since become the largest producers of animal glue. Our annual production is about 150 million pounds. Of the glue produced by the meat-packing industry, about 60 percent comes from hides and 40 percent from bones.

ANIMAL GLUES are made principally from hides, connecting tissue, cartilage, bones, and trimmings of cattle and calves, which are byproducts of meatpacking plants. Fish glues are made from fish skins, heads, and trimmings from canneries and fisheries.

Horns and hoofs, contrary to popular belief, contain no collagen or gelatin. Gelatin, or glue, is derived from collagen, a type of protein found in the raw materials I just mentioned. In the process of making and isolating gelatin, the hides are given a mild hydrolytic treatment with lime. The treatment converts the insoluble collagen into water-soluble gelatin, which is then extracted from the parent substance with warm or hot water. Collagen is regarded as the anhydride of gelatin. The tests normally used to evaluate the quality of a glue are viscosity, gel strength, melting point, and setting point. Several batches of glue may be blended to obtain a uniform product.

The gelatin-type glues are used in water solution and are valued in many uses because they form a stiff gel at low concentration. One of their chief uses is for woodworking (especially for furniture) and for products in which long working life is a great convenience but in which high water resistance is not required sandpaper, matches, gummed labels, and paper boxes. The rayon textile industry has used more than 10 million pounds of animal glue yearly as a sizing material. A good deal also goes into calcimine, paper sizing, a duplicating process, bookbinding, sizing of straw hats, rubber processing, coopering, print rollers, emery wheels, cork gaskets, and protective colloids.

Our production of animal glue from 1937 to 1939, about 60 million pounds, represented about 96 percent of the domestic consumption. By 1947 production had increased to 159 million pounds ; the later production data, although incomplete, indicate no further increases.

The United States Tariff Commission classifies photographic gelatin, pharmaceutical gelatin, and food gelatin as edible gelatin because the first two, if they do not meet their intended specifications, may be sold as food gelatin.