Investigating Changes in the Physicochemical and Structural–Functional Properties of Soybean Milk Under an Industry-Scale Microfluidization System

Abstract

Conventional thermal methods for soybean milk have several limitations, including prolonged processing times and the filtration of soybean residue. However, the application of an industry-scale microfluidization system (ISMS) offers a promising solution to these challenges. This research investigated the effects of ISMS pressure levels (80, 100, and 120 MPa) on the structural, physicochemical, and functional characteristics of wet pulverized soybean milk. Compared to wet pulverized soybean milk (1.36–255.58 μm), the maximum reduction in particle size (by 52%) and the increase in zeta potential (by 14%) were observed in soybean milk treated at 120 MPa (p < 0.05). Additionally, the reduction of free sulfhydryl content in ISMS-treated soybean milk contributed to a significant increase in surface hydrophobicity (p < 0.05). As pressure increased, the secondary structure of soybean milk proteins changed, exhibiting an increase in α-helix content and a decrease in β-sheet content. The results from endogenous fluorescence spectroscopy indicated a corresponding enhancement in fluorescence intensity. Concurrently, the spatial conformation of the protein altered, leading to the exposure of hydrophobic amino acid side chains that had previously been concealed within the molecular architecture. This exposure resulted in a progressive increase in surface hydrophobicity, ultimately achieving the maximum protein solubility. The application of ISMS treatment at elevated pressures significantly altered the structural characteristics and enhanced the physicochemical and functional properties of soybean milk, establishing a basis for its utilization in the food industry.