Enhanced tofu quality through calcium sulfate and transglutaminase treatment: physicochemical properties and digestibility analysis

Abstract Tofu, a traditional soy-based food, is widely consumed globally and serves as a significant source of plant protein. The quality of tofu can vary greatly depending on the coagulation process and the type of coagulants used. This study investigated the impact of a compound coagulant, consisting of transglutaminase (TGase) and calcium sulfate (CaSO4), on tofu quality, specifically focusing on pH, yield, water holding capacity (WHC), cooking loss, protein content, and in vitro digestibility. Soymilk was pre-crosslinked with TGase for different durations (0, 1, 2, and 3 h) before the addition of CaSO4. Results indicated that TGase pre-treatment significantly improved tofu yield and WHC, with optimal outcomes at 3 and 2 h, respectively. Cooking loss decreased with TGase treatment but increased at the 3-h mark, suggesting over-crosslinking. Electrophoresis revealed substantial protein crosslinking with TGase treatment, while in vitro digestion showed enhanced protein digestibility and higher peptide content in TGase-treated samples. These findings underscore the potential of TGase treatment to enhance tofu's structural integrity and digestibility, offering valuable insights for optimising plant-based protein processing to improve nutritional quality.