Effects of age-related gastrointestinal conditions on the digestion of myofibrillar protein-stabilized fish oil oleogel emulsions.

Fish oil has polyunsaturated fatty acids, and fish oil oleogels have potential as animal fat substitution to supplement EPA and DHA. However, age-related gastrointestinal conditions may affect disintegration and digestion of fish oil oleogel emulsion. The objective of this study was to determine how age-associated differences in gastric pH, pepsin activity, and intestinal bile salt concentration regulate the digestion-induced interfacial remodeling of fish oil oleogel-in-water emulsions stabilized by golden pompano (Trachinotus ovatus) myofibrillar proteins. The results showed that increasing pepsin activity from 1500 to 2000 U significantly increased the gastric degree of hydrolysis (DH), accompanied by unfolding, hydrophobic group exposure. Elevating gastric pH from 3.0 to 6.0 attenuated protein denaturation and hydrolysis. Low gastric pH was associated with more prominent particle clusters, whereas fewer large clusters were observed at higher pH, consistent with the corresponding results of particle size and ζ-potential. During intestinal digestion, increasing bile salt concentration from 5 to 10 mM significantly enhanced ζ-potential and interfacial replacement of MPs by hydrophobic interaction, indicating bile-salt-dependent reorganization of the intestinal digests. Thus, pepsin activity, gastric pH, and bile salt concentration regulated conformation transition, DH and interfacial behavior during simulated gastrointestinal digestion. These results can provide a mechanistic basis of developing low-fat surimi products for elderly digestive characteristics.