Nair de Los Angeles Pereira

This study aimed to develop a functional food by improving the omega-3 (n-3) fatty acid profile in Oreochromis niloticus fillets through diets formulated entirely without marine ingredients. Three experimental diets were tested: a fishmeal-based diet (Control), a chia seed meal diet (CH), and a flaxseed meal diet (FL), along with a commercial diet (Ganave®) for comparison. Fish were cultured in a recirculating aquaculture system (RAS) to evaluate growth performance and fillet lipid composition. Productive parameters showed no significant differences among treatments, indicating that replacing fishmeal with plant ingredients did not affect growth performance. However, significant differences were observed in the fatty acid profiles. Fish fed with CH and FL diets exhibited higher n-3 fatty acid levels and substantially lower n-6/n-3 ratios (0.60 and 0.63, respectively) compared to the Control (1.95) and Ganave® (2.64) treatments. Remarkably, the n-3 profiles of tilapia fillets from the CH group were comparable to those of marine species, despite the complete absence of marine-based ingredients. These results demonstrate that fully plant-based feed formulations can reproduce, and in some cases approach, the lipid nutritional quality typically associated with marine sources. Therefore, tilapia fillets obtained from chia- and flaxseed-fed fish can be classified as functional foods due to their improved n-3 content and favorable n-6/n-3 ratios. This finding highlights the potential of sustainable, plant-based aquafeeds to enhance the nutritional quality of aquaculture products while reducing dependence on finite marine resources.

Fish processing generates plenty of waste that is directly discarded in open‐air dumps and water sources, or treated in the same way as urban solid waste, causing serious pollution problems. The waste represents a significant source of high‐value bioproducts with potential applications in different industrial processes such as the production of feed, fertilizers, biodiesel and biogas, detergent additives and cosmetics. The objective of this study was to characterize and compare specific activities under different pH values and temperature conditions of acid and alkaline proteinases and viscera yield from the following fish species: Argentine hake Merluccius hubbsi, Brazilian flathead Percophis brasiliensis, Brazilian codling Urophycis brasiliensis and Stripped weakfish Cynoscion guatucupa. Individuals were fished off the coast of Mar del Plata (Argentina) by a commercial fleet and the viscera were immediately extracted and kept on ice until use. Stomach proteinases from four species had the highest activity at pH 2, with stability in the range of pH 2–4. The optimum pH was 11.5 from intestinal enzymes of C. guatucupa, M. hubbsi and P. brasiliensis and 9.5 from intestinal enzymes of U. brasiliensis. Alkaline proteinases from all species were highly stable in the range of 7–11.5. The optimum temperature of stomach proteinases from the four species studied were 30 and 50°C, with stability at 10 and 30°C during 150 min. The optimum temperature of intestinal enzymes from the tested species were 50°C with high stability at 10 and 30°C during 150 min. Alkaline proteinase from all species and acid proteinases from C. guatucupa were inactive at 70°C after 150 min, while there was a residual activity lower than 5% at 80°C on pre‐incubated stomach enzymes of M.hubbsi, P. brasiliensis and U. brasiliensis after 5, 10 and 20 min, respectively. Digestive proteinases recovered in this study could be appropriate for technological usage, reducing manufacturing costs, obtaining revenue from fishery wastes, and contributing to the reduction of environmental pollution.

Summary: Argentina is the seventh largest world producer of cheese. Owing to the profitability of this industry, more than a thousand of dairy companies and farms exclusively produce cheeses, and, thus, this activity utilises 42% of total raw milk production of the country. Due to the increase in cheese demand, and because calf rennet is relatively expensive, this has motivated the study of new sources of proteases due to the potential use in biotechnological processes. Previously, crustacean proteases have been considered as good rennet substitutes for milk coagulation during the cheese making process. The aim of this study was to evaluate and characterise acidic proteases obtained from Pleoticus muelleri discards and their proteolytic capability as well as their potential use as a milk‐clotting agent. The activity of aspartic proteases and the satisfactory acceptation by the taste panel for cheese made with shrimp's enzymes suggest that P. muelleri proteins offer a high potential for use in dairy biotechnological processes with potential use as milk‐clotting agents for cheese making.