Physicochemical and Microbiological Changes During Drying of Wolf Herring (Chirocentrus dorab) and Coastal Trevally (Carangoides coeruleopinnatus)

The aim of the present study was to assess the physicochemical and microbiological changes during sun drying of salted wolf herring (Chirocentrus dorab) and coastal trevally (Carangoides coeruleopinnatus). For that purpose, the pH value, moisture, sodium chloride (NaCl) content, total volatile base nitrogen (TVB-N), histamine, cadaverine, putrescine, tryptamine, tyramine, spermine, and spermidine, as well as total aerobic mesophilic count, amine forming bacteria, total coliforms, Staphylococcus spp., and Bacillus spp., were determined. The initial pH value was 6.4 and increased during the salt drying process to 6.9 in both cases. The initial moisture, salt, and TVB-N levels of C. dorab and C. coeruleopinnatus were 64.3 and 60.3%, 2.55 and 2.70%, and 22.8 and 16.2 mg/100 g, respectively. At the end of drying, moisture decreased to 31.3 and 35.6%, respectively; salt increased to 13.71 and 16.04%; and TVB-N increased to 35.9 and 33.13 mg/100 g, respectively. Regarding total aerobic mesophilic count, amine forming bacteria, total coliforms, Staphylococcus spp., and Bacillus spp., a statistically significant (P < 0.05) reduction of the population was observed in both cases. Regarding the biogenic amine forming bacteria, Morganella morganii and Klebsiella pneumoniae were isolated from C. dorab; Bacillus cereus, Staphylococcus xylosus, and Providencia rettgeri were isolated from C. coeruleopinnatus. During sun drying, the amount of histamine, cadaverine, putrescine, and tryptamine was reduced; spermine was detected in C. dorab only during the first day, whereas spermidine was not detected. This reduction may be attributed to the presence of biogenic amine decomposing bacteria. However, further research is necessary in order to verify in situ this capacity and exploit potential applications for fish and fishery products.