Abstract: Two different sourdoughs, named SLB02012 and SL20998, were prepared respectively with Lactobacillus plantarum B02012 and Lactobacillus alimentarius 20998, having similar acid production rate and acidification performance in this study. Also, sourdoughs SYLB02012 and SYL20998 were made with each of the two strains in combined with yeast, respectively. Traditional yeast-fermented sourdough (SY) and non-fermented sourdough made with edible organic acids (SCA) as well as non-inoculated dough with erythromycin (CK) were used as controls. Gliadin was extracted from each sourdough and was evaluated for secondary and tertiary structures and immunoreactivity by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Fourier transform infrared spectroscopy (FTIR), intrinsic fluorescence spectroscopy (IFS), enzyme linked immunosorbent assay (ELISA), and their correlation were analyzed by agglomerative hierarchical clustering (AHC). SDS-PAGE results indicated that protein hydrolysis in dough was mainly governed by lactic acid bacteria. High-molecular-mass glutenin (HMM-GS) and some gliadins in SLB02012 were more effectively degraded than in SL20998. Further, FTIR and IFS analyses indicated that the molecular flexibility of glutens in SLB02012 increased. Moreover, SLB02012 exhibited the most marked decrease in α-helix content and the smallest α-helix/β-sheet content ratio among the 7 doughs. In addition, SY, SLB02012 and SYLB02012 showed blue shifts of λmax, while SL20998 showed a red shift of λmax, implying that the tertiary structure of the proteins was extended. In terms of the immunoreactivity of gliadins as measured by ELISA , SLB02012 showed a decrease of 35% compared with CK, while no significant difference was noted for SCA and SL20998 increased by 29.5%. AHC showed a good correlation between the secondary and tertiary structures and the immunoreactiviity of gliadins for each of these sourdoughs. Taken together, Lactobacillus plantarum B02012 can be used as a dominant bacterium in low allergenic fermented foods, and this study provides theoretical support for understanding the mechanism of action of lactic acid bacteria in reducing allergenicity.

Key words: lactic acid bacteria, long-term fermentation, sourdough, protein structure, immunoreactivity