The valorization of agro-industrial residues through sustainable technologies is a promising strategy for enhancing the nutritional and functional quality of food ingredients. In this study, ultrasound extraction was applied to beetroot (Beta vulgaris L.) residue to improve its functional properties, antioxidant capacity, and in vitro bioaccessibility. Using a central composite design and response surface methodology (RSM), the effects of sonication amplitude (70–85%) and time (8–13 min) were optimized. The optimal conditions (77.5% amplitude, 9 min) significantly improved water retention capacity (12.20 g/g), oil holding capacity (10.21 g/g), and the extraction of bioactive compounds, including betanins (3327.08 mg BE/100 g dw), betaxanthins (2381.34 mg BE/100 g dw), and total phenolic content (496.95 mg GAE/100 g dw). Antioxidant activity assessed via ABTS, DPPH, FRAP, and chelating assays was also enhanced. Ultrasound treatment reduced microbial load and induced structural modifications, as observed by scanning electron microscopy, which contributed to increased fiber content and altered physicochemical properties. In vitro digestion assays revealed an improvement in the bioaccessibility of betalains, though phenolic compounds showed moderate losses, possibly due to degradation during processing. These results underscore the potential of ultrasound as an environmentally friendly and effective method for the revalorization of beetroot residue, supporting its incorporation into functional food formulations.

Bioactive compounds, Food waste valorization, In vitro bioaccessibility, Response surface methodology (RSM)