Bacterial Diversity and Changes towards Spoilage Microflora of Iced Alaska Pink Salmon

Abstract

The second batch of pink salmon (n = 4) was immediately degutted and rinsed thoroughly with tap water. Fish were placed belly down to prevent water accumulation and spaced apart on a layer of flaked ice, then covered with more ice. The totes were covered with lids and kept in the cold room. Melting ice was replenished every 24 h for 19 days. Initially and at days 4, 6 and 20, one fish was taken for sampling. Bacterial analysis On each sampling day, the fish skin and belly cavity were swabbed (area of 10 cm 2) separately for conducting aerobic plate counts [14]. Gills were aseptically cut and 25 g of sample was macerated in 225 mL of 0.1% (w/v) peptone water and serial dilutions were made in the diluent [15]. Aliquots (0.1 mL) of each serial dilution were spread-plated on duplicate plate count agar (PCA; Difco Lab, Detroit, MI) supplemented with 0.5% w/v NaCl. These plates were incubated at 25 °C for 48-72 h and then plates with 30-300 colonies were selected for counting [16]. Total number of colonies counted from duplicate plates were averaged and used to calculate log colony-forming units (CFU) per cm 2