A large proportion of consumers all across the world have crowned the soybean with the title of ‘the wonder bean’. This reputation is further fortified by active research and development efforts that continue to expand the already extensive list of soybean products resulting in tasty, cheap protein ideal for both vegetarians and non-vegetarians alike.
However, compared to other types of beans, soya requires a lot more processing because of the quality of these seeds. All the traditional routes of utilization of soybeans as food involve some sort of processing or fractionation, intended to overcome the disadvantages mentioned above.
The starting material is de-hulled beans and strict sanitary requirements are applied during processing, storage and packaging conditions, in order to secure the microbiological quality of the final product e.g. total microbial count. This includes the extraction with water as in the production of soymilk, precipitation from water extracts as in the preparation of soybean curd (tofu), and fermentation processes in the production of soybean paste, soy sauce and fermented soybean curd.
Production begins with the separation of the soybeans into two fractions: oil and meal. There are, basically two process alternatives to achieve this purpose: pressing and solvent extraction (the removal of oil using lipid solvent).
Defatted soybean flours and grits, intended for human consumption, are essentially soybean meal which has been ground to the appropriate mesh size. In addition, a large variety of products, differing in their lipid content are produced by adding-back soybean oil to defatted flour or grits at specified levels (refatting).
If defatted soybean flour with a specific moisture content is subjected to high shearing forces at high temperature in an extruder, a product with a peculiar laminar structure is obtained. After hydration (addition of water), this product presents an elastic and chewy texture resembling that of meat. Then the product is known as ‘textured soybean protein’ or ‘textured vegetable protein’ (TVP). Textured vegetable protein or TVP has a texture similar to ground beef, and tastes great when prepared with a variety of different seasonings.
How TVP is produced in a factory?
The steps in making TVP vary slightly based on the manufacturer, but in general the process is as follows. The final product often has a porous or fibrous texture that is somewhat similar to the texture of meat.
First, Soy flour is prepared and then mixed with water. The mixture is then heated at high temperature and pressure inside a machine called an extruder. The opening of the extruder is a plate with holes that come in various shapes and sizes. The heated soy mixture is pushed through the holes and cut into small pieces by blades. The pieces puff up as they leave the extruder and enter an environment with a lower pressure. The TVP pieces are then dried or baked.
TVP has a long shelf life if stored properly and is an excellent source of protein and fiber. TVP is dry and has a very low bacterial count. On the other hand, meat products can be easily contaminated with bacteria such as E. Coli and Salmonella. It meets standards of nutrition but is economical as well. Further, TVP has zero cholesterol.
Though it is not common in Sri Lanka among major TVP manufacturers, certain foreign countries add certain chemicals for the flavor and some of these flavor variations do have partially hydrolyzed oil in them for flavor and texture changes. Hydrolyzing the fat extends the shelf life when compared to using vegetable oil. This increases the fat content in some of the flavored varieties. However, with such a high fiber content, the balance is still very much on the healthy side, especially if you are making a comparison to ground beef or sausage.
The wholesome, nutritious and delicious alternative to meat
Finally, textured vegetable protein is not a whole food but a processed product. All food regulation agencies say that textured soy protein is safe, unless an individual suffers from a soy allergy.
Even in terms of cost, it is very economical and makes an excellent meat substitute in many dishes. After all, customers just purchase a dry product, and the weight greatly increases with the addition of water. For example, 1 pound of beef dehydrates down to 4 oz of jerky. Therefore, in comparison to TVP, customers are paying for 12 ounces of water per pound of meat when they purchase fresh beef!
It is a good source of the essential amino acids, and also contributes calcium and magnesium to one’s diet. TVP is also very high in potassium, acts as a good source of the essential amino acids, and contributes calcium and magnesium to one’s diet. TVP contains absolutely no meat or meat by-products, therefore those who are on strict vegetarian or vegan diets can use TVP to supplement their protein.
[The writer is Prof. Shirani Ranasinghe, Senior Prof. in Biochemistry, Department of Biochemistry at the Faculty of Medicine – University of Peradeniya.]