Accelerating the coagulation of germinated soymilk by glucono-δ-lactone using different physical treatments and quality assessment of separated soybean whey

This investigation was undertaken to assess the efficacy of glucono-δ-lactone coupled with thermal (steaming and microwave) and non-thermal (ultrasound) treatment in the coagulation of soy protein from germinated soybean seeds. The findings indicated that both microwave and ultrasonic treatments significantly accelerated coagulation of soy protein (5.4-8.7 times faster) compared to conventional steaming treatment. Regarding textural properties, soybean curd obtained from germinated soymilk displayed increased hardness values (122.0 to 277.3 g) and microwave treatment further augmented this textural attribute, except for the sonicated samples. FTIR data also confirmed that the microwave treatment was found to elevate the β-sheet content while concurrently diminishing the α-helix content within the soybean curd. Concerning the soybean whey isolated from soybean curd, the germination was shown to amplify the concentrations of the amino acids Arg, Glu, and Asp. Although the phenolic content in the whey fraction of the germinated samples was higher than that of the non-germinated samples, the FRAP activity of the microwave- and ultrasound-treated samples followed the opposite trend. Overall, microwave treatment reduced processing time while improving texture of tofu, suggesting that microwave treatment can serve as an effective processing intervention to improve both efficiency and structural properties in tofu manufacturing.