English

Abstract

This paper identified the bacterial flora composition and its influence on the microbiological spoilage process in economically important fish species: Filhote (Brachyplatystoma filamentosum) and Dourada (Brachyplatystoma rousseauxii) in the Amazon region. Microbiological characterization was performed: counts of total mesophilic aerobic bacteria, psychrotrophic bacteria and coliforms at 35 and 45°C, respectively. Bacteria were also isolated through seeding in agar surface using Violet Red Bile Glucose (VRBG) for enterobacteria strains and Baird-Parker Agar with Egg-Yolk Tellurite for Staphylococcus species, both with incubation at 36°C for 48 h. The bacteria isolated were identified using the API 20E kit (Enterobacteria), and Gram-positive bacteria with API Staph (Staphylococci). Finally, the lag phase for strain growth was measured using spectrophotometry readings (620 nm) at different temperatures (10, 15 and 37°C). The mesophilic aerobic bacteria counts for fresh fish samples ranged from 5.21 to 7.64. The count ranges of psychrotrophic aerobic bacteria found were 5.11 – 6.91 log CFU/g. They also had an average score above 103 MPN/g for total coliforms. The most predominant were Hafnia alvei, Pseudomonas luteola, Staphylococcus xylosus and Staphylococcus lugdunensis. When subjected to temperature of 10°C, the strains achieved growth after 6 h (p<0.05). Key words: Spoilage, catfish, Brachyplatystoma filamentosum, Brachyplatystoma rousseauxii.