Protein-lipid film (fuzhu) prepared from soymilk: Effects of soymilk convection on its formation, composition, and quality

Fuzhu (or yuba), a popular Asian soy food, is a protein–lipid film isolated from soymilk surface through high-temperature incubation. The convection of soymilk during incubation is relevant to the formation and property of fuzhu. This study aims to clarify this hypothetical relation and highlight the manipulatable incubation factors for qualified fuzhu production. Hydrochloric acid and guar gum were applied to modify the rheological and thermophysical properties of soymilk, which resulted in a series of model soymilk that underwent various convection during incubation. Fuzhu films prepared from these model soymilks were evaluated for their compositions and visual and textural qualities. The relation between the properties of fuzhu and the convection mode of soymilk was discussed. Results demonstrated that the formation of fuzhu occurred when soymilk underwent time-dependent convection. Fuzhu became less tension-resistant and exhibited visual defects with the reduction of convection intensity. Moreover, factors including the viscosity, height, and temperature gradient of soymilk may be considered for the optimization of incubation. The outcome of the present study may support the innovations of fuzhu and other plant protein-based foods.