Gastrointestinal digestion impact on phenolics and bioactivity of tannat grape pomace biscuits

Abstract

The search for natural sources of bioactive compounds with health-promoting properties has intensified in recent years. Among these, Tannat grape pomace (TGP), a primary byproduct of winemaking, stands out for its high phenolic content, although its bioactivity may be affected during gastrointestinal digestion. This study aimed to evaluate the impact of in vitro digestion on the antioxidant (ABTS, ORAC-FL, intracellular ROS inhibition), antidiabetic (α-glucosidase inhibition), anti-obesity (lipase inhibition), and anti-inflammatory (NO inhibition) properties of five sugar-free biscuits formulated with varying percentages of TGP and sucralose. No significant differences were observed in the bioaccessible fractions (BFs, representing the compounds potentially released in the small intestine) between control biscuits and those enriched with TGP, suggesting limited release of phenolics at this stage. Conversely, the colonic fractions (CFs, simulating the material reaching the colon) from biscuits with higher TGP content exhibited greater bioactivities. HPLC-DADMS analysis of the CF from the biscuit containing 20% TGP and 4% sucralose revealed a high content of procyanidin trimers, indicating the persistence of these specific phenolic compounds after in vitro digestion. These findings suggest that TGP-enriched biscuits may deliver health benefits at the colonic level and support their potential application in the formulation of functional foods. Further microbiota and in vivo studies should be assessed to confirm the latter.