Evaluation Microbiologique et biochimique du thon rouge Thunnus thynnus (Linné, 1758) mis en conserve

Abstract

The processing and canning of seafood is an agro-food industry that strengthens a country’s economy and contributes to job creation. This sector allows access to migratory and non-native species from fishing areas on the one hand, and on the other hand, it integrates these canned species, such as bluefin tuna (Thunnus thynnus), into daily meals throughout the year. This research study is presented in two parts: the evaluation of nutritional value parameters on one hand, and bacteriological culture of canned samples A, B, and C of bluefin tuna (Thunnus thynnus) on the other hand. Pollution, particularly bacteriological, can harm the health of biodiversity, thus threatening both the survival and sustainability of marine species. The estimation of nutritional value primarily involved mathematical calculations to determine the percentage of dry matter, water content, lipid extraction, and stability tests conducted on samples A, B, and C by measuring pH after preparing a solution containing distilled water and a fragment of tuna flesh. Concurrently, bacteriological culture using specific media such as PCA for total germs, 0.1% deoxycholate agar for total coliforms and fecal coliforms, Baird-Parker agar (BP) for Staphylococcus aureus, and liver veal for sulfite-reducing Clostridium allowed for phenotypic identification of germs from the mother solution and various decimal dilutions in physiological water. Macroscopic observation of the three canned tuna samples revealed no deformation, leakage, unpleasant odor, or swelling. The percentage of dry matter (DM%) for samples A, B, and C was evaluated at 58%, 60%, and 68%, respectively. The results indicated water content for each sample as follows: 42% for A, 40% for B, and 32% for C. The lipid percentage was estimated at 52% for A, 41% for B, and 49% for C. It was observed that sample A had the highest lipid content, followed by sample C. Regarding the stability test, the hydrogen potential (pH) results for samples A, B, and C incubated at 37°C and 55°C ranged between 6 and 7, while those kept at room temperature in the laboratory were recorded at 6. However, according to the results obtained from colony counts after culture from decimal dilutions, bacterial concentration values did not exceed the guideline values according to the official microbiology journal, as was the case for total germs, total coliforms, Staphylococcus aureus, and sulfite-reducing Clostridium. In conclusion, this study on canned bluefin tuna (Thunnus thynnus) conducted during February, March, April, and May indicated that samples A, B, and C presented good nutritional quality, and bacteriological cultures were generally negative in reference to the guideline values from the official microbiology journal, concluding that this batch of canned bluefin tuna is safe for consumption.