Production of aroma-rich extracts from sardine cooking wastewaters: exploring their potential for modulating feed intake in European seabass

Managing the canning industry’s nutrient-rich and odorous liquid waste is a hurdle. Concurrently, the growing use of vegetable ingredients in aquafeeds diminishes palatability and feed consumption in carnivorous fish. Thus, we hypothesized that aromas could be extracted from cooking wastewaters at canning factories and added to plant-based diets to stimulate intake in European seabass. Sardine cooking wastewaters were collected and tested directly (CW-A) or after vacuum distillation (VD-A) or liquid/liquid extraction with soybean oil (LLE-A). Despite losses in aldehydes and short-chain alcohols, both processes were effective in removing off-flavours. VD-A displayed a higher concentration of most aromas compared to LLE-A. Extracts were included at 2 μg g⁻¹ of 1-penten-3-ol, the most abundant compound in all extracts, in diets (CW, VD, LLE). A non-supplemented diet was used as control. Each diet was assigned to six groups of juvenile fish, fed a single meal until apparent satiation. Our emphasis was on this initial feeding to comprehend the hedonic control of feed intake, minimizing habituation effects and the impact of the long-term metabolic requirements. Feed intake was highest for the control group. No differences on plasma metabolites were observed, suggesting feed intake was primarily regulated by hedonic rather than homeostatic mechanisms. Moreover, the lower intake in the supplemented diets was partially associated with a lower expression of orexigenic (intake-promoting) neuropeptides and higher expression of anorexigenic (intake-reducing) neuropeptides in the brain, despite the lack of significant diet-related differences. Overall, this study presents a novel approach to valorise cooking wastewater from the canning industry, since cooking wastewaters extracts rich in aromas were successfully produced, however, in the tested concentration, had no positive impact on the short-term feed intake response of European seabass.