Microbiological contamination of tilapia (Oreochromis niloticus) during the fish processing

Abstract

The aim of this study was to evaluate the microbiological contamination of the tilapia (Oreochromis niloticus) fillet and the water used at various stages of processing in an industry located in the metropolitan area of Curitiba - PR. Samples were collected in five stages of the fillet processing. Water was collected in the two first steps of processing and the tilapia fillet was collected in the last three steps. Collection and analysis of samples were performed in four replicates. Tilapia fillets were subjected to the viable count of aerobic psychrotrophic, total coliform and Escherichia coli, coagulase-positive Staphylococcus and Salmonella sp. Water samples were subjected to the most probable number of coliform and Escherichia coli. Psychrotrophic count ranged from 4.3 x10⁶ CFU/ g for fillet after de-skinning to 2.6 x10⁷ CFU/ g for fillet after packaging. The occurrence of coagulase-positive Staphylococcus was only detected in fillet after packing and the viable number was lower than 10³ CFU/ g. Salmonella was detected in tilapia fillet after de-skinning and after removing the central spine. With regard to the water contamination by total coliform and Escherichia coli numbers were in accordance to the standard established by Brazilian law. However, fillet samples showed coliform and E. coli contamination at all stages of tilapia processing with values ranging from 5 x 10¹ to 4.5 x 10³ CFU/ g of total coliform and <10 to 3.0 x 10² CFU/ g of Escherichia coli. The results showed the need for better microbiological control of the fillet and the water during the tilapia processing, because high counts of spoilage microorganisms and the presence of pathogens were found in all studied processing stages.