IN-VITRO DIGESTION AND STABILITY OF MICROPARTICLES FORMED BY COMPLEX COACERVATION CONTAINING TANNIC ACID

Tannic acid (TA) is a polyphenol produced from the secondary metabolism of higher plants. In addition to presenting antioxidant activity, anti-inflammatory activity and anticarcinogenic properties, TA can interact and bind non-specifically to different proteins, especially α-amylase, contributing to the treatment of diabetes and obesity. TA microparticles were produced from double emulsion followed by the complex coacervation between lactoferrin (Lf) and High methoxyl pectins (HMP) in the ratio of 10:1 (Lf:HMP) and pH 5.5 and the encapsulation in a ratio of 1:0.15 (wall:core) and concentration of biopolimer of 0.5%. This study aimed to evaluate the resistance of microparticles to pH conditions and heating time and to study the release of TA along the simulated gastrointestinal system and its bioaccessibility at the end of in vitro digestion. The results showed that the particle size of TA microparticles (25 °C) varied as a function of pH (2.0-9.0), with the smallest size (750 nm) at pH 5.5 and the largest (3280 nm) at pH 9.0. The stability reduction can be explained by the reduction of electrostatic interaction between the Lf and HMP molecules as a function of the proximity to the pI of the protein. In contrast, when subjected to heat treatment (80 °C), the size of TA microparticles (pH 5.5) ranged from 750 nm (0 min) to 170 (20 min) possibly due to protein denaturation. Despite the variation in particle size, the formation of precipitates was not verified in any of the studied treatments. With respect to in vitro digestion, TA release occurred slowly during the simulated digestive system. In the mouth, there was only 18% release, reaching 37% release in simulated gastric fluids after 120 minutes of digestion. The slow release of TA in the gastric phase can be explained by the structure formed by the complex and a favorable pH (3.0), in addition to the crosslinking action of transglutaminase. In the intestinal phase, there was a rapid release of TA (69%) in the first 30 minutes of digestion, due to the simultaneous action of pH (7.0), pancreatic enzymes and bile, which promote the dissociation and demulsification of the microparticules. At the end of the in vitro digestion the bioaccessibility of TA was 38%. Microparticles can be an effective system for the encapsulation and controlled release of other hydrophilic bioactive compounds, such as polyphenols. In addition, Lf:HMP microparticles can enable the controlled release of tannic acid and its viable arrival in the intestine, to then inhibit -amylase and exert its anti-hyperglycemic function.