New Fermented Beverage from Orange Peel By-Products Containing Bioactive Flavanones

The increasing popularity of fermented beverages, such as kombucha, has prompted the search of alternative ingredients with distinct functional and sensory properties. Orange (Citrus sinensis L. Osbeck) peel, an abundant by-product of the citrus industry, represents a valuable natural source of flavanones associated with multiple health benefits, offering a suitable substrate for fermentation. In this context, the present study proposes the valorisation of this by-product through the development of a new fermented beverage analogous to kombucha, rich in bioactive flavanones. During the fermentation process, variations were observed in physicochemical quality parameters (pH (4.86–2.91), titratable acidity (maximum 0.45% as acetic acid), and total soluble solids (TSS) (6.90–7.05 °Brix), as well as in the fermentation metabolites and substrates: sucrose (73.99–45.75 g/L), fructose (0.98–6.87 g/L), glucose (1.60–1.35 g/L), ethanol (0.06–0.24 g/L), and acetic acid (0.45–3.00 g/L). On the other hand, the initial total flavanone content (11.85 mg/100 mL), of which 70% corresponded to hesperidin, decreased during fermentation but then remained stable, reaching a final concentration of 5.72 mg/100 mL. Overall, these results highlight the potential of orange peel by-products for the development of innovative fermented beverages with a high content of bioactive flavanones, which are distinct from conventional tea-based kombucha. Moreover, this strategy represents a potential approach for this citrus waste valorisation, contributing to improved resource efficiency and supporting the transition towards a circular economy.