Effects of Different Particle Sizes of Ultrafine Indica Rice Flour and <scp> <i>Lactobacillus casei</i> </scp> on the Fermentation and Flavor Characteristics of Danling Dongba

This study aimed to enhance the flavor and quality of Danling Dongba, a traditional fermented rice product, by preparing ultrafine indica rice flours using fluidized bed airflow crushing. Flours with particle sizes of 20.16, 17.16, and 12.22 μm were fermented with <i>Lactobacillus plantarum</i> 550 (<i>L. plantarum</i> 550), <i>Lactobacillus fermentum GF1800</i> (<i>L. fermentum</i> GF1800), and <i>Lactobacillus paracasei S6 (L. paracasei</i> S6) under optimized conditions. The 12.22 μm flour showed the best performance, with a water absorption index of 2.32 g/g, solubility of 2.05%, swelling power of 9.26 g/g, and peak viscosity of 7632.53 cP. Solid-phase microextraction coupled with GC × GC-MS revealed that <i>Lactobacillus</i> fermentation increased volatile flavor compounds from 42 (unfermented) to 72. Notably, <i>L. plantarum</i> 550 enhanced fruity esters such as ethyl caprylate (1.18%), while <i>L. paracasei</i> S6 enriched milk-like ketones such as 3-hydroxy-2-butanone (1.54%). These findings demonstrate that optimizing flour fineness and <i>Lactobacillus</i> strains can significantly improve the flavor complexity of Danling Dongba, offering a scientific basis for its standardized production and industrial development.