Influence of Processing Schemes on Indicative Bacteria and Quality of Fresh Aquacultured Catfish Filletst†

Abstract

Fresh aquacultured catfish fillets were obtained from three processors using different processing protocols in summer, autumn, winter, and spring and evaluated for microbial quality. Twenty freshly processed fillets were randomly selected and each fillet was placed in a sterile polyethylene bag. The fillets were transported on ice-pack overnight by air immediately after processing. Five fillets were randomly selected for microbial assays. Each fillet was weighed and an equal volume of sterile 0.1 % peptone water at 0 to 1°C was added aseptically. The fillet was massaged (or rinsed) for 120 s and the rinse was used to determine microbial quality. Aerobes (incubation at 35°C for 48 h) and psychrotrophs (incubation at 20°C for 96 h) were enumerated using 3M Petrifilm™ Aerobic Count plates. Escherichia coli (incubation at 35°C for 24 to 48 h) and total coliforms (incubation at 35°C for 24 to 48 h) were enumerated on 3M Petrifilm™ E. coli Count plates. Staphylococcus aureus counts were determined on Baird-Parker agar (incubation at 35°C for 48 h). Significant differences (P ≤ 0.05) in aerobic, psychrotrophic, total coliform, E. coli, and S. aureus counts due to temperature effects during production and variations in processing protocols were observed. E. coli and S. aureus counts were significantly different during the four seasons. E. coli and S. aureus counts were high during summer and low during winter weather. There was a significant difference (P ≤ 0.05) in aerobic, psychrotrophic, and total coliform counts among the three processors during warm weather; however, these differences were significantly (P≤ 0.05) reduced in cold weather.