2006 Volume 53 Issue 1 Pages 39-47
In a reusing process of waste okara by the incorporation into tofu, the treatment of the okara hydrolysate (okara milk) and original soymilk mixture with transglutaminase (TGase) is required for the complete gelation of whole soymilk. To perform this enzymatic treatment economically, several immobilized microbial TGases were prepared with three support types and bioselective complexation between avidin (A) and biotin (B). The enzymatic activity of the immobilized TGase was either determined by benzoyloxycarbonyl-L-glutaminyl-glycine and hydroxylamine or the whole soymilk as a substrate (50°C, 30min). Of the prepared enzymes, the TGase immobilized on Lewatit VP OC 1065 resin, Lew-B-A-B-TGase, was selected as a practical biocatalyst given that it exhibited the highest specific enzyme activity. A breaking test of tofu prepared from the whole soymilk treated by Lew-B-A-B-TGase, with conventional coagulants such as glucono-δ-lactone showed an increase in breaking strength compared to untreated samples. In addition, the same immobilized TGase exhibited good operational stability, maintaining 100% of its initial activity even after 10 cycles of cross-linking of the soy proteins in the whole soymilk.
