Refractometer Evaluation of Eye’s Nile Tilapia in Correlation to their Sensory and Bacteriological Qualities
Refractometer Evaluation of Eye’s Nile Tilapia in Correlation to their Sensory and Bacteriological Qualities
Ali Meawad Ahmed1, Asmaa I.A. Morsy1, Rehab E.M. Gaafar2, Nada Ibrahim H. Ahmed1
ABSTRACT
Advances in the efficiency of fish freshness are crucial for optimizing quality assessment, and enhancing consumer safety. This has created the need for developing a novel method which can easily monitor fish quality and ensure trade safety in the fish markets. Therefore, the aim of the present study was to investigate the application of a refractometer device in the freshness and quality assessment of the Nile tilapia by measuring the fish eye’s fluid salinity and its correlation to sensory and bacteriological parameters. A total of 150 Nile tilapia samples were sensory evaluated by the quality index method, then bacteriologically evaluated for total bacterial, enterobacteriacae counts, and for the incidence of E. coli and Salmonella. In addition, the fish eye’s fluid salinity was measured by a portable refractometer. In the experimental part, 80 fresh tilapia fish were stored in ice for 8 days and periodically evaluated at 24-houres intervals. Results of the current study revealed that the mean value of the sensory score of tilapia was 3.68 demerit points (maximum 21 with the lowest quality). It was obvious that 52% of samples were graded symbol A with excellent quality, 32.6% were graded symbol B with good quality, and 15.3% were graded symbol C with acceptable quality, while none of the examined samples were rejected. The mean values of total aerobic counts and enterobacteriacea counts were 3.20 x104 and 5.69 x 101, respectively. The incidence of E. coli and Salmonella was 38% (n=57) and 0.67% (n=1), respectively. Serological identification of isolates revealed that the E. coli were O78:k80, O158:k-, O26:k60 and O114:k90, while the only Salmonella isolate was S. entertidis. Moreover, the mean value of the eye’s fluid salinity was 6.61%. There were significant positive correlations (p<0.05) between the eye’s fluid salinity on one and sensory and bacteriological results. Furthermore, the obtained results showed a significant increase (p<0.05) in fish eye’s salinity along the storage period which strongly correlated with changes in total bacterial and enterobacteriacae counts. In conclusion, fish eye’s salinity can be used as a novel quality criterion for Tilapia freshness using a refractometer. It is a valid support for managing perishable fish commodities and preventing possible consumer risk as well.
Keywords: Quality, Eye salinity, Nile tilapia, Refractometer, Sensory, Bacteriological
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October 2024
Vol. 12, Sp. Iss. 1
