Valorization of Restaurant Vegetable Residues as Sources of Natural Pigments and Antioxidants for Sustainable Aquaculture Feed Development

Aquaculture is one of the fastest-growing food production sectors worldwide; however, feed represents up to 70% of production costs, creating a demand for sustainable and cost-effective functional ingredients. Vegetable residues generated by institutional food services are rich in natural pigments and bioactive compounds that can be recovered and incorporated into aquafeeds, contributing to the circular economy and blue bioeconomy while reducing food waste.

This study evaluated the bioactive potential of beetroot (Beta vulgaris) and red cabbage (Brassica oleracea var. capitata f. rubra) residues collected from the University Restaurant of the Federal University of Pelotas (Capão do Leão, Brazil). Natural pigments were extracted using environmentally friendly solvents and characterized by pigment content, antioxidant capacity, and total phenolic compounds.

Beetroot residues contained 30.65 ± 0.08 mg betacyanins (betanin equivalents, BE)/100 g fresh weight, together with antioxidant activities of 197.19 ± 4.35 mg TE/100 g (DPPH) and 342.67 ± 45.82 µg TE/g (ABTS), and 69.13 ± 1.46 mg GAE/100 g of total phenolics. Red cabbage residues exhibited 34.4 ± 0.2 mg cyanidin-3-glucoside equivalents (C3G)/100 g, high antioxidant capacity (4091.2 ± 48.8 µg TE/g by DPPH and 12,757.3 ± 2,126.8 µg TE/g by ABTS), and 69.1 ± 1.5 mg GAE/100 g of total phenolics. The mixed extract contained 34.2 ± 0.8 mg C3G/100 g, 17.59 ± 0.13 mg BE/100 g, 4475.20 ± 63.92 µg TE/g (DPPH), 1394.3 ± 56.1 µg TE/g (ABTS), and 47.40 ± 0.42 mg GAE/100 g.

These results demonstrate that vegetable residues from institutional restaurants are valuable sources of natural pigments and antioxidant compounds that can be recovered through green extraction technologies. Their incorporation into aquaculture feeds could partially replace synthetic pigments while providing functional antioxidant ingredients, reducing feed costs, promoting waste valorization, and supporting circular economy and blue bioeconomy strategies. Furthermore, this research provides the scientific basis for the development of an innovative startup focused on sustainable functional ingredients for aquaculture.