Effect of Aqueous and Ethanolic Kiwifruit Peel Extracts on the Functional and Sensory Properties of Kefir

This study explores the valorization of kiwifruit peel, a nutrient-rich agro-industrial by-product, as a functional ingredient in kefir within the framework of sustainable food systems. Aqueous and ethanolic extracts of kiwifruit peel were incorporated into kefir, and their effects on antioxidant capacity (CUPRAC, FRAP, DPPH), total phenolic content, in vitro bioaccessibility, physicochemical properties, and sensory attributes were evaluated. Ethanolic extracts exhibited higher initial antioxidant activity, whereas aqueous extracts showed significantly greater phenolic bioaccessibility after simulated gastrointestinal digestion. The addition of extracts significantly affected color parameters, viscosity, and consistency (p < 0.05). Sensory analysis demonstrated that enriched samples were well accepted, with favorable flavor and texture profiles. These findings highlight the potential of kiwifruit peel as a sustainable bioactive ingredient in fermented dairy products.