The microstructure of soy-based products, including homogeneous colloidal dispersion in soymilk, dense protein networks in tofu, and lipid-protein films in yuba, directly influences protein accessibility during simulated digestion, with more aggregated structures resulting in delayed enzyme penetration and reduced early-phase digestibility.

When soy proteins are heated and processed into dense structures like yuba or tofu, they form tightly locked networks held together by strong chemical bonds and rigid sheet-like folds. These structures resist breaking open in the stomach and intestines, so digestive enzymes cannot reach the protein inside. Only after bile breaks down the surrounding fat layers can enzymes finally reach and break apart the trapped proteins, delaying digestion.