Okara is produced in large quantities annually in China, but much of it is discarded due to its high content of indigestible dietary fiber (DF), contributing to significant environmental challenges. Recognizing the underexplored medicinal potential of DF, we developed an efficient fermentation method to enhance the bioavailability of okara fiber. In this study, Pediococcus acidilactici IFJ-1, which has strong enzymatic production capabilities and beneficial effects on gastrointestinal flora modulation, was selected to ferment okara. Results showed decreases in viscosity and particle size, optimized surface structure, improved thermal stability and hydration properties, and a significant increase in soluble DF content from 1.85% to 3.91%. To evaluate the physiological effects, hyperlipidemic mouse models were established and subjected to dietary interventions utilizing okara and fermented okara to measure changes in physicochemical parameters, gut microbiota composition, and lipid metabolism. The dietary intervention was effective, particularly in the fermented okara group, showing a 7.3% weight loss, improved blood lipids (triglycerides: ‒39.8%, total cholesterol: ‒12.8%, low-density lipoprotein cholesterol: ‒34.2%, high-density lipoprotein cholesterol: +26.2%), and a 22.2% lower liver index. Gut microbiota analysis revealed that fermented okara positively modulated the microbial community by increasing the abundance of beneficial bacteria (e.g., Bacteroidota) and reducing the abundance of obesity-associated bacteria (e.g., Bacillota). Lipid metabolism profiling further demonstrated that fermented okara downregulated harmful lipids (e.g., (O-acyl)-ω-hydroxy fatty acids, ceramides, and diacylglycerols) while upregulating beneficial phospholipids (e.g., phosphatidylinositol, phosphatidylserine, phosphatidylethanolamine, lysophosphatidylinositol and lysophosphatidic acid). This study highlights a novel approach for enhancing DF utilization through fermentation, providing valuable insights into strategies for preventing obesity and metabolic diseases.

This study investigated the effect of freezing ball milling treatment on the structure, properties and digestibility of waxy rice starch, prepared by alkaline extraction. The effects of treatment time on the particle size distribution, microstructure, crystalline structure, short-range ordered structure, pasting properties, thermodynamic properties and digestibility of waxy rice starch were examined. The results showed that after freezing ball milling treatment, the integrity of starch granules was damaged with cracks appearing on the surface, the particle size tended to increase, and the crystalline structure and short-range ordered structure were severely damaged. The water absorption index increased from 2.15 to 7.31 g/g, and the cold water solubility and swelling power increased significantly from 2.97% and 3.25% to 46.33% and 15.50%, respectively in the 80 min ball milling group compared with untreated samples (P < 0.05). The enthalpy change (ΔH) decreased from 9.33 to 1.79 J/g, and the degree of gelatinization significantly increased (P < 0.05). The birefringence of the starch gradually disappeared with increasing treatment time. The rapidly digestible starch (RDS) content of waxy rice starch increased significantly (P < 0.05), while the contents of resistant starch (RS) and slowly digestible starch (SDS) decreased significantly (P < 0.05). This study provides basic data and references for the production of modified starch products with novel structures and properties.