Antioxidant Capacity and In Vitro Bioaccessibility of Phenolic Compounds in a Functional Fruit–Spice Beverage Enriched with Inulin and Myo-Inositol

The growing demand for healthier beverages has boosted the development of fruit-based functional drinks, but their real potential depends not only on initial bioactive content but also on the fraction that remains available after digestion (bioaccessibility). This study evaluated the antioxidant capacity and in vitro bioaccessibility of bioactive compounds in a beverage formulated from pineapple, apple, ginger, and cinnamon extracts, with inulin and myo-inositol as complementary ingredients. Three formulations were prepared: F1 (fruit–spice extract), F2 (F1 + inulin), and F3 (F1 + inulin + myo-inositol). Physicochemical parameters (pH, °Brix, reducing sugars, dietary fiber), total phenolic content (Folin–Ciocalteu), and antioxidant capacity (ABTS and FRAP) were measured before and after an adapted INFOGEST gastrointestinal digestion. Bioaccessibility was calculated from the intestinal supernatant. All formulations had pH 3.61, but soluble solids increased from F1 to F3 (6.17–8.97 °Brix). Folin–Ciocalteu values decreased after digestion in all formulations, but F1 retained the highest bioaccessibility (95.05 ± 5.82%), while F2 and F3 showed much lower values (33.28 ± 2.01% and 39.17 ± 5.52%, respectively). ABTS values increased after digestion in all formulations, with bioaccessibility exceeding 100% (125–143%). In contrast, FRAP values dropped sharply after digestion (bioaccessibility 4.59–11.00%), with F2 and F3 showing slightly higher retention than F1. The antioxidant response after digestion is strongly method-dependent and influenced by the beverage matrix. The formulation without inulin and myo-inositol (F1) better preserved the reducing capacity measured by Folin–Ciocalteu, while enriched formulations showed higher FRAP retention. ABTS bioaccessibility increased universally, suggesting release or transformation of radical-scavenging compounds during digestion. This study supports the need to include bioaccessibility assays when evaluating the functional potential of complex fruit-based beverages.