Stability of bioactive compounds from Thai Riceberry bran extract encapsulated within gelatin matrix during in vitro gastrointestinal digestion

Abstract

Digestive stability of developed capsules of bioactive compounds from Riceberry bran extract was investigated by applying simulated in vitro gastrointestinal digestion model to assess the recovery of bioactive compounds entrapped within two types of gelatin: acid-processed (type A) and alkaline-processed (type B) gelatin. The physicochemical properties, namely, net surface charge (ζ-potential) and average particle size (Z-average), of the extract and gelatin in the solute state were used to explain the effects of gelatin type and concentration on the in vitro digestion stability of produced capsules. Extracts encapsulated with positively charged type A gelatin exhibited greater encapsulation efficiency and percent recovery of bioactive compounds (exhibiting a net negative charge) and increased antioxidant activity as measured by ferric reducing antioxidant power assays during simulated gastrointestinal digestion than those entrapped with negatively charged type B gelatin. This result indicated that electrostatic interactions were the main force affecting gelatin-based capsule formation. Moreover, the highest Z-average was found in 2% (w/v) type B gelatin (475.57 nm) due to the high rate of intermolecular bond formation, resulting in higher viscosity than that obtained with a concentration of 1% (w/v), which may block the interaction between gelatin and bioactive compounds. Therefore, extracts encapsulated with 2% type B gelatin yielded the lowest percent recovery values for bioactive compounds. The overall results showed that net surface charge and particle size of gelatin affected the in vitro gastrointestinal digestion stability of bioactive compounds from Riceberry bran extract.