Effect of ohmic heating on fundamental properties of protein in soybean milk

Abstract The structure and functional properties of heated soybean milk protein were measured and compared between ohmic heating (17, 23, 30, and 37 V/cm) and common resistance wire heating. The results showed that the number of free amino groups increased by 14%; total sulfhydryl content and surface hydrophobicity decreased; the protein structure was not significantly changed; functional properties and foaming activity were reduced by 10, 15, 35, and 40% for the different voltage ohmic heating; foam stability was reduced by 28.3, 12.9, 18.3, and 8.3%, respectively; the EAI of ohmic heating increased by 38%, whereas the ESI decreased by 65%. Soybean protein has been reported to be denaturalized in traditional heating. As a resistor, in situ vibration was conducted inside the molecule when it is heated via electricity. It can be assumed that ohmic heating is conducive to the improvement of functional properties, digestion, and absorption of soybean milk protein. Practical applications This study explored effects of voltage ranges on soybean milk quality and structure and functional properties. After ohmic heating treatment, the structure and functional properties of protein in soybean milk greatly changed relative to traditional heating treatment. The application of ohmic heating for soybean milk was found very successful in reducing heating time and producing nutrient products. The same goes for the other fruit and vegetable products, it is of great directive significance to ohmic heating processing industry for them.