Reduction of Gliadin Antigenicity in Steamed Buns Using Commercial Yeasts: Structural and Immunological Insights

To investigate the effect of yeast fermentation on the antigenicity of gliadin in steamed buns, eight commercial yeast strains were used to prepare steamed buns from Zhengmai 7698 flour. Gliadin antigenicity was assessed by ELISA kit, whereas the changes of protein structure were analyzed by Fourier transform infrared (FTIR) spectroscopy, particle size measurement, and surface hydrophobicity determination. The results showed that there are variations in gliadin antigenicity among steamed buns prepared with different yeast strains. Notably, the antigenicity of steamed buns prepared with the Apple brand yeast decreased significantly (by 9.7%). Fermentation and steaming disrupted the gliadin structure, resulting in a 27% reduction in α-helix content and helix unwinding. Subsequent protein aggregation led to a significant 30.8% increase in average particle size and a significant 58% decrease in surface hydrophobicity index. Concurrently, the intensities of both ultraviolet (UV) absorption and endogenous fluorescence spectrum were significantly reduced, attributed to the embedding of chromogenic amino acids within the molecule during aggregation. These findings demonstrate that commercial yeast strains can alter the antigenicity of gliadin in steamed buns, and that fermentation and steaming modify the structure of gliadin.