Kinetics of Phenolic Compound Release from the Peel of the Traditional Apple Variety 'Kolačara' During in vitro Gastrointestinal Digestion

The peel of traditional apple varieties represents a rich source of phenolic compounds, known for their potential health benefits. This study investigated the release kinetics of phenolic compounds from the peel of the traditional apple variety ‘Kolačara’ during simulated gastrointestinal digestion using a modified first-order kinetic equation. During digestion, anthocyanins and flavan-3-ols were undetectable after the intestinal phase, while dihydrochalcones, phenolic acids, and flavonols demonstrated greater stability. Kinetic analysis revealed that the release followed first-order kinetics. During the gastric phase, half-life values ranged from 2.3 to 7.9 minutes, indicating that most phenolic compounds were released within the first 10 minutes of digestion. In the intestinal phase, half-life values reached up to 2.4, 6.6, and 31.1 minutes for phenolic acids, flavonols, and dihydrochalcones, respectively. The study highlights the rapid release of phenolic compounds from the peel of a traditional apple variety peel, with dihydrochalcones showing the highest resistance to intestinal degradation. These findings provide valuable insight into the digestive behavior of bioactive compounds derived from valuable traditional fruit sources.