Sequential extraction of polysaccharides from enzymatically hydrolyzed okara byproduct: physicochemical properties and in vitro fermentability

Abstract

Okara, a byproduct of soymilk production, has been upgraded through the use of an enzymatic treatment with Ultraflo L® to give a product (okara(ET)) which has a higher content of soluble dietary fibre and an enhanced ratio of soluble: insoluble fibre than is found in okara without treatment. Polysaccharides were isolated from okara(ET) by sequential extraction to yield soluble fractions in water (22%), CDTA (8.7%), alkali (37.7%) without and NaClO2 (9.1%) and the cellulosic residue represents a (22.5%). The physicochemical properties of okara(ET) were improved due to the enzymatic treatment: oil retention capacity (6.94g/g), water retention capacity (10.76g/g) and swelling capacity (13.85g/g) were higher than in okara that had not undergone enzymatic treatment. The gelation capacity (8%) and the cation exchange capacity (8.96mEq/kg) of okara(ET) were lower than that of other byproducts. Short chain fatty acid production during in vitro fermentation of okara(ET) by a pure culture of Bifidobacterium bifidus was mainly represented by acetic acid, followed by propionic and butyric acids. In addition, the decreases in pH and substrate consumption demonstrated the bifidogenic capacity of okara(ET).