Soybean Trypsin Inhibitors: From Anti-Nutritional Factors to Beneficial Physiological Agents and Delivery Applications

Soy protein isolate is widely used in modern food systems, yet its industrial processing produces large volumes of whey wastewater rich in diverse components, including soybean trypsin inhibitors. Traditionally regarded as antinutritional factors due to their ability to impair protein digestion, soybean trypsin inhibitors have been extensively studied in the context of food safety and nutritional quality. However, recent perspectives have shifted from viewing them solely as antinutrients toward recognizing their biofunctional potential, particularly as natural delivery vehicles for bioactive compounds. This review comprehensively examines conventional and emerging strategies for the isolation, purification, and inactivation of soybean trypsin inhibitors, with emphasis on structure-function relationships influenced by processing. Moreover, we highlight a paradigm shift in their application-from undesirable factors to functional ingredients-specifically focusing on the feasibility of soybean trypsin inhibitors as natural vehicles for active peptide delivery. This evolving role underscores their promising utility in advanced food-based delivery systems and functional food development.