Quality assessment and processing of Cobia (Rachycentron canadum) from fish farming

Author: Marcondes Agostinho Gonzaga Junior (Currículo Lattes)
Supervisor: Dr Carlos Prentice Hernández


In recent years, the Cobia Rachycentron canadum has attracted worldwide interest. In Brazil, there are still few studies aimed at generating packages to make its creation feasible, much less for the development of technologies for its processing. The effective consolidation of aquaculture depends on the flow of production, which, in turn, will depend on the demand for products. In order for the consumption of fish in Brazil to be increased, it is necessary to offer products with the quality required by the consumer. Thus, the present study aimed to assist the technology developed for whole and minimally processed fish. Specimens of bijupira cultivated in net tanks (near-shore system) and in a water recirculation system were used, fed with commercial feed and fishing tailings, with a variable weight from 2 to 3 and 9 to 11 kg.After fishing, the fish were sacrificed by hypothermia in cold water (thermal shock method, 1: 1 ratio, ice: water). Sensory, physical-chemical and microbiological alterations were investigated in the cultivated bijupirá in order to determine the conservation time in ice and frozen of the whole fish and its fillet. For the study of conservation on ice, the fish were stored in Styrofoam boxes, followed by two research variants: 1) After sacrificed by thermal shock, the specimens were stored on ice for 30 days, where they were evaluated, in each 2-day interval, post-mortem quality changes, through chemical analysis (nitrogen of the total volatile bases - N-BVT and pH), sensory (quality index method - MIQ of whole fish) and microbiological (mesophile counting) , psychotrophs,psychrophils and total coliforms); 2) Dynamic monitoring of useful life, with the applicability of a smart photochromic indicator with smart tags (ITT). For the study of frozen storage, the bijupirá fillets were processed and frozen in a plate freezer (-30 0C) and stored in a freezer at -18 0C, for 180 days, where, in each interval of 30 days, pH, oxidation test (TBA), moisture, proteins, instrumental fillet hardness and the same microbiological analyzes performed for fish preserved on ice. The technological potential of this species was also evaluated, in the form of fillet packaged in a modified atmosphere and packaging with different films, packed in plastic bags of high density of ethylene-alcohol-vinyl - EVOH. The samples were submitted to 3 treatments:A (Control) and 2 more atmospheres containing approximately 0.5 L of air: (100% CO2) and (Vacuum). The packaged samples were kept under refrigeration, in the range of 2 ± 1oC, when they were subjected to analysis at times 0,1,7,14,21,30,45 and 50 days of refrigerated storage in a heated oven. Physical-chemical analyzes (total volatile bases - N-BVT, pH), lipid stability (TBA), texture (breaking strength), color and microbiological analyzes were performed. Still working with packaging, the effect of nanocomposite biofilms from fish protein isolate (IPC) on the quality of the fillets kept under refrigeration was evaluated. The CPI was obtained from by-products of the industrialization of fish. Polymeric films were developed from IPC using the casting technique. Three types of films were tested,two industrial and one prepared based on IP: TA (EVOH), TB (PVC), and TC (IPC), submitted to the same analysis of packaging with EAM. Thus, we conclude that the sensory analysis of fish packaged on ice showed a point of rejection with 15 days of storage. In the fillet packaged under a modified atmosphere, vacuum and 100% CO2 packaging have extended the shelf life for up to 21 days at refrigerated temperature. When packaged under vacuum, the results showed that the frozen fillet under these experimental conditions has evident sensory, chemical, physical, and microbiological stability stored at -180C for 180 days. The packaging of nanocomposite films made from IPC proved to be efficient for the conversation of chilled fish in relation to commercial films.