FROM GASTRIC TO COLON: HOW MILK MATRIX AFFECTS THE STABILITY AND RELEASE OF COCOA PHENOLICS

Abstract

This study evaluated in vitro bioaccessibility of phenolic compounds in cocoa beverages formulated with different milk matrices, such as full cream milk (CF), skim milk (CS), and whey protein powder (CW), compared to a control without milk. Samples underwent sequential gastric (pepsin, pH 3) and intestinal (pancreatin and bile salts, pH 7) simulated digestion following INFOGEST protocol. Quantification of total phenolic and flavonoid was using spectrophotometric assays, and compound‐specific profiling was achieved by UHPLC‐HRMS. Results showed that although incorporation of dairy matrices led to an initial decline in total phenolic content of undigested sample, it enhanced phenolic retention during simulated digestion. Significant increase of phenolic bioaccessibility was observed in the intestinal phase, with CS formulation achieving the highest phenolic bioaccessibility index (129.71 ± 5.99 %). Total flavonoid content declined progressively during digestion in all samples. UHPLC‐HRMS analysis identified 10 phenolic compounds in undigested CS sample, but only two of those phenolics still detected in intestinal phase. Hydrolysis of insoluble fractions that resulted from intestinal digestion released additional bound phenolics, suggesting potential colonic release and absorption. These findings highlight the role of milk matrices, particularly skim milk, in improving phenolic bioaccessibility of cocoa beverages. However, the use of a static in vitro digestion model represents a limitation, as it cannot fully replicate dynamic human gastrointestinal condition. Future studies should explore in vivo validation, apply dynamic digestion models, and assess the metabolic fate and biological activity of released phenolics following colonic fermentation.