EFFECT OF MICROWAVE HEATING ON THE VISCOELASTIC PROPERTY AND MICROSTRUCTURE OF SOY PROTEIN ISOLATE GEL

Abstract

ABSTRACTThe effect of microwave heating on the viscoelastic property and microstructure of soy protein isolate (SPI) gel was investigated by using a dynamic rheometer and a scanning electron microscope. SPI suspension was either heated in a boiling water bath for 10 min or microwaved for different lengths of time, and then was coagulated by adding glucono‐δ‐lactone (GDL) or calcium sulfate to form an SPI gel. The gelation mechanism of SPI suspension was affected by heating method and coagulant type. GDL was more appropriate for SPI gel formation when the microwave heating was used for protein denaturation. It was clearly observed that applying a moderate microwave heating time on SPI suspension could produce a gel with distinct viscoelastic properties and microstructure.PRACTICAL APPLICATIONSSoy protein isolate (SPI) is widely utilized as an ingredient in many food systems. The heating condition and the coagulant type affect the gelation of SPI, leading to a wide range of gel texture. Microwave heating is an efficient and energy‐saving thermal processing. It can preserve more nutrients in the product and is widely accepted by the food industry. The viscoelastic property and microstructure are important parameters for evaluation of the gel texture. To the best of our knowledge, the application of microwave heating on soy processing has not been studied before. Findings in this research can be used for further applications of microwave heating on tofu processing.