Matrix-Dependent Remodeling of an RG-I-Rich Pectin Fraction during INFOGEST Digestion of Golden Delicious Apples: Intact Pulp vs Processed Homogenate

The gastrointestinal structural fate of pectin is a key determinant of its nutritional relevance; however, most available studies rely on isolated polymers and do not account for the influence of the native food matrix. Here, we tested whether the apple tissue state governs post-digestive remodeling of an RG-I-rich pectic fraction during in vitro gastrointestinal digestion (INFOGEST), comparing intact Golden Delicious apple pulp with a processed homogenate. In undigested samples, the polymeric (>10 kDa) water-extracted RG-I-enriched pectic fraction (WERP) showed comparable RG-I fingerprints in both matrices. After digestion, a clear divergence emerged: pulp-derived WERP showed pronounced RG-I side-chain loss and an approximately order-of-magnitude decrease in apparent molecular weight, whereas homogenate-derived WERP largely retained its pre-digestive fingerprint. Digestion of isolated apple pectin did not reproduce these changes, consistent with a key role of tissue context and processing history.