Soymilk fermentation and enzymes production

Abstract

Soy products have an excellent status for their high protein content, and soy proteins contain enough of all the essential amino acids to meet biological requirements when consumed at the recommended level of protein intake. However, soybeans, as well as other legumes, characteristically contain high concentrations of antinutritional factors such as α-galactooligosaccharides (α-GOS) and phytates that can inhibit the absorption of many essential nutrients and cause serious physiological problems. Hydrolytic digestion of α-GOS is relatively weak in mammals because they do not possess α-galactosidase (α-Gal) in the upper gastrointestinal tract. The indigestibility of these soluble carbohydrates results in their delivery into the colon where they are rapidly fermented by the resident microbiota resulting in the production of large amounts of gas. This induced flatulence greatly hampers the acceptability of soy products as a major food source for humans and animals. The use of microbial α-Gal is a promising solution for the degradation of these undesirable α-GOS. Phytates, a common component of soybeans and grains can hinder the ability of humans (and other animals) to absorb crucial minerals such as calcium, magnesium, iron, and zinc. Certain microorganisms produce the enzyme phytase that degrades phytates and therefore may potentially improve mineral bioavailability and absorption. This chapter will discuss the use of lactic acid bacteria (LAB) that produce α-Gal and/or phytates in order to improve the nutritional value and acceptability of soy-based products.