Effect of microwave and conventional heat treatment on trypsin inhibitor activity and in vitro digestibility of edamame milk protein

Abstract

Edamame milk is a protein-dense milk derived from green soybeans harvested before they mature. Being a legume of soy origin, it contains antinutritional factors for example, serine protease inhibitors, which hinder its in vitro digestibility. The objective of this study was to evaluate the effect of microwave processing techniques in improving the in vitro digestibility (IVPD %) of edamame milk protein by varying processing time and temperature. Conventional and microwave-assisted processing was employed to investigate the effect on in vitro protein digestibility (IVPD %), using temperatures 70°Ϲ, 85°Ϲ, and 100°Ϲ for 5, 10, and 15 min, respectively. Fourier-transform infrared (FTIR) data showed microwave and conventional treatments significantly modified the Amide I region of the edamame milk protein and the extent of modification varied with variation in the treatment temperature. In the FTIR analysis β-sheet content was observed to change little with an increase in the temperature, suggesting similarity in the surface hydrophobicity of the protein leading to similar IVPD % values for all treatment temperatures. The experiment resulted in increased in vitro digestibility with increasing time and temperature during microwave processing conditions and conventional thermal conditions. It was also observed that the trypsin inhibitor activity decreased with an increase in processing time and temperature.