The effect of type II Rice bran sourdough with dominant lactic acid bacteria (with evaluated antimicrobial & co-aggregation potentials) on pan bread quality using RSM

This study focused on enhancing bread quality by incorporating type II rice bran sourdough (RBS) fermented with Pediococcus stilesii, a dominant lactic acid bacteria species isolated from spontaneous RBS. P. stilesii exhibited robust coaggregation ability (48.32% ± 2.4), strong antimicrobial activity against Escherichia coli (27.46 ± 0.41 mm inhibition zone), and moderate activity against Staphylococcus aureus (27.23% ± 0.25 coaggregation ability, 10.53 ± 0.68 mm inhibition zone). It also displayed antifungal properties against Aspergillus niger. Using Response Surface Methodology (RSM), the study optimized key parameters in RBS bread formulation: sourdough content (15%, 25%, and 35%), fermentation time (16, 24, and 32 h), and substrate concentration (0.5%, 1.5%, and 2.5%). Results indicated that substrate concentration and fermentation time significantly influenced bread characteristics such as chewiness (164.1 ± 31.7; p < 0.05), porosity (39.64 ± 1.33; p < 0.05), browning index (187.35 ± 6.62; p < 0.05), and overall acceptance (4.38 ± 0.09; p < 0.05). Sourdough content and fermentation time significantly affected hardness (9.207 ± 2.93; p < 0.05), chewiness, specific volume (2.58 ± 0.084; p < 0.05), porosity, and overall acceptance. The optimal parameters identified were 18.61% sourdough content, 23 h of fermentation, and 2.1% substrate concentration. These parameters maximized quality traits, confirmed by second-degree modeling, goodness-of-fit tests, and response evaluations, paving the way for improved bread formulations using this novel sourdough technology.