Consumers appreciate European seabass when fed innovative diets committed to a circular economy

Poultry by-product meal (PM), defatted Hermetia illucens meal (HM), the invasive crayfish Procambarus clarkii meal (CM) and dried microalgae biomass (MA) are examples of nutritious and sustainable aquafeed ingredients[1,2]. Ten diets were tested on the European seabass Dicentrarchus labrax: a vegetable-based diet (CV); a fishmeal-based diet (CF); eight diets prepared by replacing 10, 20 or 40% of the plant proteins in CV with HM or PM singly or together (HP), with CM, or with MA. Firstly, fillet quality of fish and fillets were fully characterised, then, fish underwent a blind consumer test. MA diet efficiently increased the yellowness index of fish skin (p<.05), similarly to what found in Sparus aurata[2], while no effect on fillet colour emerged (p>.05). Dietary HM and PM increased fillet texture (52.8, 78.3, 91.9 and 80.0 N in CV, HM40, PM40 and HP; p<.01). Fillet fatty acid profiles reflected the dietary ones, in line with the literature[3], except for docosahexaenoic acid, whose content did not vary in fillets belonging to different groups (5.8g/100g total fatty acid). Consumers’ liking for odour, flavour and texture was high in HM, PM, and HP fillets, as found in Salmo salar and Oncorhynchus mykiss fed HM or PM[3,4]. Besides, the highest intention of reconsumption was expressed for HP fish (89%), while the other groups ranged between 78 and 84%. In conclusion, a possible functional effect of MA emerged, while HP seemed a feasible and promising combination for D. labrax nutrition. However, an insight into the metabolic mechanism behind these positive results is necessary for a comprehensive knowledge of fish qualitative aspects. References: 1. Maiolo, S. et al. Int. J. Life Cycle Assess. 2020, 25, 1455–1471; doi.org/10.1007/s11367-020-01759-z. 2. Pulcini, D. et al. Animals 2020, 10, 02138; doi.org/10.3390/ani10112138. 3. Bruni, L. et al. J. Sci. Food Agric. 2020, 100, 1038–1047; doi.org/10.1002/jsfa.10108. 4. Bruni, L. et al. Aquaculture 2021, 543, 736996; doi.org/10.1016/j.aquaculture.2021.736996.