Comparing physical properties of retort-resistant glucono- δ-lactone tofu treated with commercial transglutaminase enzyme or low levels of glucose

Abstract

A commercial transglutaminase enzyme or glucose at concentrations of ⩽5 mg/mL was added into soymilk during the production of glucono- δ-lactone tofu. The tofu was cut into pieces, packed with water in a can and retorted at 115°C for 20 min. The commercial enzyme was used to induce a formation of epsilon-(- γ-glu)Lys cross-links within the tofu structure, whilst glucose was used to induce glycation of basic amino acid side chains of protein molecules of the tofu. Addition of transglutaminase enzyme or glucose suppressed retort-induced water release; however, the effect was more pronounced in tofu treated with commercial enzyme. Hardening of texture of tofu occurred during retort cooking, and increased with transglutaminase concentration but was not affected by the addition of glucose. The results suggest the possibility of using either commercial transglutaminase or low levels of glucose for production of retort-resistant tofu.