Effects of heat treatments on the properties of soymilks and glucono- δ - Lactone induced tofu gels.

Optimal heat treatment of the soymilks is important to the production of tofu. In this study, soymilk with protein concentration of 40 mg/mL were heated at different temperatures for the fixed 50 s and were characterized by surface hydrophobicity, disulfide linked protein species determined by non-reducing SDS-PAGE and protein structural elements determined by the circular dichroism (CD). Tofu gels were prepared by acidifying the heated soymilks at 60 ℃ and 80 ℃ respectively and gelation time, gel mechanical properties as well as gel viscoelastic properties were determined by rheological analysis. The results showed that most soymilks' properties except surface hydrophobicity changed rapidly when heating temperature was higher than 80 ℃. Gelation time, storage modulus (G') at the end of acidifying and cooling processes as well as retardation time (λ) and recovery rate of tofu gels were affected by the heat treatments of soymilks. The distances between the standardized data describing heated soymilks and tofu gels respectively were calculated and compared. It was found that gelation time, G' and λ were most closely related to disulfide bond linked polymer, [CD] ₂₂₂ and surface hydrophobicity respectively. This study will provide useful information to the improvement of tofu processing.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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