Lactobacillus plantarum F25-4 assisted rice soaking reduces the cooking strength of japonica rice for Chinese rice wine brewing

This study investigated the effect of Lactobacillus plantarum F25-4 assisted rice soaking (LAS) on the cooking properties of japonica rice used for Chinese rice wine (CRW) production. The effects of LAS and natural soaking were compared based on the chemical composition, thermal characteristics, infrared spectroscopy and sodium dodecyl sulphate-polyacrylamide gel electrophoresis of rice flour. After LAS, the protein content of the rice was reduced by 17.63%, and the initial temperature (To), peak temperature (Tp) and conclusion temperature (Tc) were reduced by 36.86%, 17.89% and 1.61%, respectively, as revealed by differential scanning calorimetry analysis. The Zeta (zeta) potential value changed from -8.75 mV to -3.99 mV, and the minimum cooking time was reduced by 40% to only 15 min. The viscoelasticity of LAS rice increased after gelatinisation, as confirmed by confocal laser scanning microscope images. The glutelin precursor of the LAS rice disappeared, and the disorder of protein secondary structure increased, but there was no significant difference in the starch crystal area. LAS effectively improved the cooking properties of rice by changing the protein configuration on the surface of starch granules and reducing protein adsorption, leading to increased starch water absorption and decreased rice gelatinisation temperature. Our research suggests that LAS can reduce the cooking temperature of rice in CRW production, thus saving steam consumption during cooking.