Protein products antinutritional factors

Preparation of dry beans involves preliminary hydration followed by various heat treatments to obtain a tender, palatable product. Water and heat play an important role in chemical reactions, heat transfer and chemical transformations, such as protein denaturation and starch gelatinization. Inadequate water uptake may result in insufficient heat transfer to inactivate antinutritional factors and result in reduced cookability. In general, beans with an initial moisture content between 12 and 18%, are soaked to hydrate the seed to a moisture content of 53 to 57% and subsequently blanched, cooked or canned. This cooking step, if done for an optimal time, renders the seed nontoxic, improves digestibility, develops acceptable flavor and softens the seed coat and cotyledon. 

Toasting of soybeans by heating at 100-1 lO C to inactivate lipoxygenase and antinutritional factors (e.g. trypsin inhibitor) is important to improve the quality of soybean protein products used for either animal feed or human consumption. However, this thermal enzyme inactivation is not carried out in the conventional processing of soybean oil. Therefore, the soybean flakes must be solvent extracted without delay to minimize free fatty acid and peroxide formation in the extracted crude oil and to produce a finished oil of improved oxidative and flavor stability. 

Several processes for the manufacture of protein concentrates or isolates for aquaculture have also been developed. These technologies yield nondenatured proteins with better digestibility for fish nutrition. Membrane separation techniques are used to separate oilseed components, remove antinutritional factors, and fractionate protein for fish feed production. 

Nowadays, most breakfast cereals are made either by original traditional processes or by using alternative extrusion methods. Commercial flakes, shreds, and oven-puffed cereals could be alternatively manufactured via extrusion. There are two major types of extrusion processes cold and thermoplastic. Cold extrusion is almost exclusively applied for production of pasta products (Chapter 10), whereas thermoplastic extrusion is used for manufacturing breakfast cereals and snack foods (Chapter 12). Undoubtedly, the most popular and versatile extrusion process is thermoplastic, defined as the combination of heat and mechanical shear to enhance starch gelatinization and dextrinization, protein denaturation, and inactivation of microorganisms, enzymes, and antinutritional factors. The changes in the properties of the starch and proteins result in the formation of a plastic material that could be formed and/or restructured into desired configurations. 

Fermentation is known to improve protein quality due to higher nitrogen digestibility and the de novo production of some amino acids such as lysine and tryptophan. In addition, these processes lower the presence of antinutritional factors (Chavan and Kadam 1989a). 

But usually it is very difficult for a new oilseed species to compete favorably with established crops. A new crop needs a great investment in the selection of varieties. A crop must have good agronomic properties so that it can grow well in diverse environments, resist diseases, not scatter its seed before harvest, and have all its seeds ripen over a relatively short period. For an oilseed crop, additional selection for high oil production, desirable fatty acid composition and meal protein may be necessary. The presence of antinutritional and toxic factors may have to be minimized or eliminated. 

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