Comparison of Gel Properties of Tofu Prepared with Different Amounts of Physalis
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Abstract:
After preparing soybean milk from soybeans of the same variety, different proportions of physalis (20%, 23%, and 26%) were added. The influence of physalis addition on the gel characteristics of the resulting tofu was analyzed by determining the texture, chemical force, SDS-PAGE pattern, microstructure, infrared spectrum, and other metrics. The texture of tofu was enhanced with increasing amounts of added physalis; the hardness of tofu reached a maximum value of 3.53 N when 26% of physalis was added. Under these conditions, the water content, water retention, and yield of tofu decreased significantly (p<0.05), whereas the protein content increased from 13.09% to 15.28%. Disulfide bonds and hydrophobic interactions were the main forces driving tofu formation containing physalis, accounting for more than 90% of the total forces, whereas the contribution of ionic bonds and hydrogen bonds was relatively low. Hydrophobicity in 7S proteins was the main force driving gel formation. Some A subunits of 11S proteins were connected by ionic bonds and hydrogen bonds to form the gel. In contrast, macromolecular protein aggregates as well as B and A3 subunits of 11S proteins mainly participated in gel formation through disulfide bonds. As the amount of added physalis increased, the gel network structure of the resulting tofu gradually became rough, and the α helix content decreased from 16.00% to 15.83%. Random coils decreased from 16.04% to 15.80%, and β turns decreased from 34.12% to 33.57%, whereas β folds increased from 33.84% to 34.80%. In summary, the amount of added physalis significantly affects the gel properties of tofu.
