EFFECT OF WHEY-PROTEIN ON TEXTURIZATION OF RENNET CASEIN

Effects of the addition of whey protein isolate (WPI) and soy protein isolate (SPI) on the texturization of rennet casein were investigated. Three types of textured casein products which were made from rennet c asein alone (control), a blend with WPI, and a blend with SPI, respect ively, were prepared. WPI and SPI were blended with rennet casein at a level of 5% on a dry basis. Fibrous structure of the textured product which was made from rennet casein alone tended to deteriorate during storage. Fibrous structure of the product blended with WPI was satisfa ctory, while that with SPI was even inferior to that of rennet casein alone. Surface hydrophobicity of each textured product was determined by using 1-anilino-8-naphthalene-sulfonate (ANS) and hydrophobic gel c hromatography. Fibrousness of textured products were found to be close ly related as inversely proportional to hydrophobicity. The product bl ended with WPI, showing the lowest hydrophobicity, revealed the highes t fibrousness among the three types, while the product blended with SP I, with the highest hydrophobicity, resulted in the poorest fibrousnes s. It was considered that an addition of WPI to rennet casein possibly prevented mutual adhesion of fibrous structure in the resultant produ ct due to a decrease of hydrophobicity, whereas an addition of SPI pro moted the adhesion due to an increase of hydrophobicity.