Effect of Static Magnetic Field on the Structure and Physicochemical Properties of Fermentation Products of Armillaria mellea

The effect of Armillaria mellea fermentation alone and combined with static magnetic field on the structure and physicochemical properties of zein was explored. Fourier transform infrared (FTIR) spectral analysis showed that static magnetic field treatment changed the secondary structure of the protein during the fermentation process. The analysis of ultraviolet (UV) absorption spectra and intrinsic fluorescence spectra showed that static magnetic field treatment resulted in protein unfolding and group exposure. The results of scanning electron microscopy (SEM) showed that after static magnetic field treatment, the surface of the protein became rougher with obvious pores and increased specific surface area. The results of thermodynamic analysis showed that static magnetic field treatment obviously increased the denaturation temperature of the protein, decreased the particle size, increased the absolute value of the zeta potential, and resulted in increased content of free sulfhydryl groups and decreased content of disulfide bonds. In addition, the physical and chemical properties of the protein were significantly changed by static magnetic field-assisted fermentation. The water and oil retention capacities, emulsification properties, foaming capacity and foam stability were increased significantly, reaching maximum values of 3.86 g/g, 4.22 g/g, 26.83 m²/g, 37.67% and 58.12%, respectively on the 7th day of fermentation. The emulsion stability was decreased significantly, reaching a minimum level of 34.10% on the 7th day. In summary, static magnetic field-assisted fermentation of zein by A. mellea can change its structure of and effectively improve its physical and chemical properties, thereby improving the added value and utilization rate of zein.