Effect of enzymatic hydrolysis on allergen-related protein degradation and physicochemical properties in a raw soybean-based extrusion system

In this study, raw soybean-based extrudates (RSBE) were used as model products to evaluate the effects of enzymatic pretreatment on allergen-related proteins, structure formation, and physicochemical properties. Soybeans were subjected to controlled hydrolysis using flavourzyme, bromelain, or papain to achieve graded protein fragmentation. Enzymatic treatment enhanced protein extractability, with papain yielding the highest soluble protein content, whereas SDS-PAGE showed progressive degradation of major allergen-related proteins, including β-conglycinin, glycinin subunits, and Gly m Bd 30K. Bromelain induced the most extensive proteolysis. Western blot analysis revealed a marked reduction in immunoreactive protein bands, suggesting reduced antibody-recognizable immunoreactivity beyond molecular weight reduction alone. During low-moisture extrusion, enzymatically hydrolyzed soybeans remained processable but exhibited pronounced changes in surface morphology, color, and structural integrity compared with the untreated control. Texture profile analysis, scanning electron microscopy, and X-ray micro-computed tomography consistently demonstrated that protein hydrolysis impaired the continuity of the extruded protein network, while proximate composition was only minimally affected. Overall, these results reveal a structure–function trade-off in which enzymatic hydrolysis effectively reduces soybean allergen-related proteins but compromises protein network formation during extrusion, providing mechanistic insight into how allergen-related protein degradation through enzymatic hydrolysis influences subsequent structure formation and texture-related functionality during extrusion. • Enzymatic hydrolysis promoted protease-dependent degradation of soybean allergen-related proteins. • Major allergen-related proteins, including β-conglycinin and Gly m Bd 30K, were reduced after hydrolysis. • Protein hydrolysis significantly affected the extrusion behavior of raw soybean-based extrudates. • Structural integrity and textural properties of RSBE were altered by enzymatic pretreatment. • A trade-off was observed between allergen-related protein reduction and structural functionality