Abstract: The thermal properties, solubility and secondary structure of soybean 11S glycinin were measured by using differential scanning calorimetry, the Lowry method and Fourier transform infrared (FTIR) spectroscopy, respectively. The effects of heat treatment on the solubility and secondary structure of 11S glycinin were evaluated. The results obtained showed that Td and ΔH were reduced by heat treatment, leading to partial or complete denaturation of protein. Heat treatment at 80 ℃ could reduce the solubility of soybean 11S globulin, which may be due to the changes in the spatial structure and surface charge of protein caused by heat treatment. At the same time, the α-helix structure of protein was gradually transformed into β-sheet and random coil structure. However, the solubility of protein was slightly increased after heating for a certain time at 90 or 100 ℃, which was ascribed to the formation of soluble aggregates. Furthermore, the α-helix and β-sheet structures of protein were transformed into β-turn and random coil structure, indicating that the β-turn and random coil structures play an important role in the formation of heat-induced aggregates. In addition, protein denaturation and rupture of hydrogen bond were important causes for mutual transformation of the secondary structures.

Key words: heat treatment, 11S glycinin, solubility, secondary structure