Abstract: Dietary fiber, recognized as the “seventh essential nutrient”, plays a critical role in human metabolic regulation and health maintenance. Okara, a by-product of soybean processing, is rich in insoluble dietary fiber (IDF) but contains only a small amount of soluble dietary fiber (SDF). SDF has garnered extensive attention due to its significant nutritional value and functional bioactivities (antioxidant effects, regulating gut microecology and blood sugar levels). However, okara products have coarse texture and poor processing performance due to their high IDF content, restricting their application in the food industry. Therefore, enhancing the solubility of okara dietary fiber (by chemical, biological, physical, or combined treatments) can promote the conversion of IDF to SDF effectively, improve its physicochemical properties and biological activity, and is of considerable importance for its promising applications in flour products, baked foods, dairy products, functional beverages and degradable packaging materials. This review systematically summarizes various modification methods to improve the solubility of okara dietary fiber and their efficacy in enhancing SDF yield, and examines the functional activities of modified okara dietary fiber with a focus on its application potential in food products. The aim of this review is to provide valuable references for theoretical research and practical utilization of okara dietary fiber, thereby promoting its wider adoption in the food industry.

Key words: okara; dietary fiber; solubilization modification; functional activities; food applications