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Thermal aggregation behaviour of soy protein: characteristics of different polypeptides and sub‐units

He, Xiu‐Ting, Yuan, De‐Bao, Wang, Jin‐Mei, Yang, Xiao‐Quan
Journal of the science of food and agriculture 2016 v.96 no.4 pp. 1121-1131
beta-conglycinin, glycinin, heat, heat treatment, hydrophobicity, pH, polypeptides, protein aggregates, soy protein, temperature
BACKGROUND: Due to the differences in structure and composition of glycinin and β‐conglycinin, they exhibit different characteristics during heat treatment. In present study, the thermal aggregation behaviour of glycinin, β‐conglycinin and their isolated sub‐units was investigated at pH 7.0. RESULTS: Acidic polypeptides, basic polypeptides, αα′ and β sub‐units of soy protein were denatured during the isolation process. The degree of aggregation of protein fractions after heat treatment was in the order: denatured basic polypeptides > native glycinin > denatured β sub‐unit > native β‐conglycinin > denatured acidic polypeptides > denatured αα′ sub‐units. Glycinin, β‐conglycinin, acidic polypeptides and αα′/β sub‐units exhibited different changing trends of surface hydrophobicity with increasing temperature. The αα′ sub‐units showed higher ability to suppress thermal aggregation of basic polypeptides than β sub‐units during heat treatment. The β sub‐units were shown to form soluble aggregates with glycinin after heating. CONCLUSION: The interaction mechanism of αα′ and β sub‐units heated with basic polypeptides was proposed. For the β sub‐units–basic polypeptides mixed system, more hydrophobic chains were binding together and buried inside during heat treatment, which resulted in lower surface hydrophobicity. The αα′ sub‐units–basic polypeptides mixed system was considered to be a stable system with higher surface hydrophobicity after being heated. © 2015 Society of Chemical Industry