Processing-Driven Changes in Phenolic Composition and Antioxidant Functionality of Aronia Snacks: Insights from In Vitro Gastrointestinal Digestion

The mechanistic impact of drying technologies on phenolic stability and gastrointestinal bioaccessibility in aronia remains poorly defined, limiting the development of functionally optimized dried berry products. This study aimed to comparatively evaluate the effects of different drying techniques—hot air drying (60, 70, and 80 °C), vacuum drying (60, 70, and 80 °C; 150 mbar), and microwave drying (180 and 360 W)—on total phenolic content (TPC), total antioxidant capacity (TAC) assessed by DPPH, CUPRAC, and FRAP, and total monomeric anthocyanins (TMA) during in vitro gastrointestinal digestion. UHPLC-DAD analysis showed that the phenolic profile was dominated by chlorogenic acid, catechin, caffeic acid, epicatechin, and quercetin. Drying enhanced extractable TPC, while TAC with DPPH and FRAP showed increasing trends and CUPRAC decreased after drying. Color changes indicated increased redness and pigment concentration following dehydration. Simulated digestion induced substantial losses in TPC (53–59%) and TMA (30.5–72.8%), alongside marked reductions in FRAP and CUPRAC, whereas DPPH activity increased significantly, suggesting matrix-driven transformation and release of antioxidant compounds under gastrointestinal conditions. Among the applied methods, vacuum drying (70 °C; 150 mbar) exhibited superior stability in terms of antioxidant and anthocyanin preservation during digestion. Overall, the findings demonstrate that drying-induced structural modifications play a key role in governing phenolic stability and bioaccessibility, providing new insights into the mechanisms underlying the functional behavior of dried berry products.