Effect of alkaline pH shift combined with sonication on the structural and functional properties of peanut protein

In order to improve the functional properties of peanut protein, alkaline pH shift (pH12 and pH13) was used to treat peanut protein alone or in combination with ultrasound (500 W/5 min and 30 min), and the changes of peanut protein structure, function and lysalanine content before and after treatment were studied. The results showed that all treatments could improve the surface hydrophobicity of peanut protein and red-shift the maximum emission wavelength of endogenous fluorescence. Among them, pH12 offset combined with long-term ultrasonic treatment, pH13 offset alone or combined with ultrasonic treatment could also significantly increase the content of soluble aggregates of peanut protein, reduce α-helix and increase β-turn in the secondary structure. Shifts of pH12 or pH13 alone significantly increased the content of lysine in peanut protein, while the combination of ultrasonic treatment could reduce the content of lysine by 60-66%. The solubility and emulsification of peanut protein were improved by pH13 offset combined with low-intensity ultrasonic treatment, and the solubility of peanut protein was increased by 19%, the emulsifying activity and emulsion stability index were increased by 56% and 271%, respectively, and the freeze-thaw stability of the emulsion was significantly enhanced. pH13 offset combined with ultrasonic treatment can not only significantly improve the functional properties of peanut protein, but also effectively inhibit the production of lysalanine, so it is a protein complex modification technology with high application potential.