Soy protein isolate (SPI) aqueous solutions were investigated for denaturation under different mechanical treatments without the addition of any chemicals. Compared with the traditional magnetic stirring treatment (MS), high-intensity ultrasonication (US), high-speed mechanical shearing (SH) and their combined treatments (USSH, SHUS) were able to dissolve better and further swell and deform the globular structures of the SPI. Higher solubility, lower turbidity, enlarged particle size, more uniform particle size distribution, higher free sulfhydryl group content, and higher viscosity were detected from the SPI solutions after US and SH treatments. Among all samples, the SPI solution after USSH treatment demonstrated that the soy proteins were denatured and possessed the most extended conformational structure. A schematic structure model illustrating the dissolution and denaturation of SPI under the treatments was established. The denatured protein solutions could relax back and degrade after storing still for up to 12 days. Furtherly, extreme pH conditions, the addition of glycerol, together with a combination of ultrasound and shear treatments (USSH) were applied to increase the solubility of SPI in aqueous solutions and denaturation the globular structure of soy proteins. USSH treatment was proved capable of increasing the solubility of SPI under extreme pH conditions, such as very high and low pH values. Also, the addition of glycerol was able to assist the dissolution of SPI in the solution and also provide antimicrobial and SPI structural stabilizing functions. With stable increased viscosity, higher content of sulfhydryl groups, and larger particle size, 30% and 50% Glycerol-H<sub>2</sub>O solvent systems were proved to be compelling solvent systems to assist the protein denaturation under the USSH treatments. The results could help the development of soy proteins in material applications.

Sustainable conformational modification of soy proteins by physical and chemical treatments

2019 Fall National Meeting

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