Screening of Superior Lactic Acid Bacteria from Sourdough and Optimization of Freeze-Dried Bacterial Powder Preparation Technology for Steamed Buns

To address the industrialization limitations of traditional sourdough and develop high-performance direct-vat-set (DVS) starters for steamed buns, this study screened superior lactic acid bacteria (LAB) and optimized the preparation technology of freeze-dried bacterial powder. The results demonstrated that the compound system of Lactiplantibacillus plantarum and Streptococcus thermophilus at a 1:1 ratio achieved favorable synergistic fermentation with sourdough, which effectively regulated dough acidification and improved the comprehensive sensory quality of steamed buns. The critical processing parameters, including centrifugation conditions and compound lyoprotectant composition containing trehalose, lactose and skim milk powder, were systematically optimized to significantly enhance the freeze-drying survival ability of compound LAB, and the high fitting degree of the established regression model confirmed the stability and reliability of the optimized formulation. The optimal dosage of freeze-dried DVS powder was verified to rationally modulate dough acidity and comprehensively promote the specific volume, structural characteristics and sensory performance of steamed buns. This systematic study provides robust theoretical and technical support for the industrial application of DVS LAB starters in high-quality steamed bun production, facilitating the modernization of traditional fermented wheat products.