Structure–Function Relationships in High-Moisture Meat Analogues: Effects of Soybean Residue (Okara) on Plant Protein–Starch Gels

Okara, a fiber-rich soybean byproduct, can improve the sustainability of plant-based meats but may compromise texture when used at high levels. This study investigated the effects of okara flour (0–40%) on the structure–function relationships of high-moisture meat analogues (HMMA) formulated with soy protein isolate, wheat gluten, and corn starch. Analyses included composition, macrostructure, instrumental texture (cutting tests and TPA, evaluated by PCA), SDS-PAGE, and pasting behavior under both pressurized and atmospheric conditions. Increasing okara decreased protein density but increased fiber and fat, resulting in nutritional trade-offs. Fibrous anisotropy was preserved up to 20% okara but declined at higher levels, producing dense, isotropic matrices. Texture analyses revealed reduced firmness, cohesiveness, and elasticity, consistent with SDS-PAGE evidence of diminished 7S and 11S subunits. Rheological tests indicated suppressed starch swelling yet greater viscosity stability under pressure. Overall, moderate okara incorporation increased dietary fiber without fully compromising texture, whereas higher levels disrupted protein alignment and gel functionality.