Isolation and Identification of Histamine-Forming Bacteria in Frozen Skipjack Tuna (Katsuwonus Pelamis)

In this study a series of experiments were carried out to detect and identify histamine-forming bacteria and analyze histamine content for evaluation of current harvesting and post harvesting procedures. the target fish was skipjack (katsuwonus pelamis) in which the samples were collected from oman sea waters harvested by gillnet or purse seine methods. bacteriological isolates and the amount of histamine were obtained from the muscle around the gills. the obtained results indicated that the average of total and psychrophilic counts were 7.2×106 and 2.9×10⁶ cfu/g, respectively. histamine-forming bacteria occurred on a low scale of total bacterial load with the mean of 2.8 ×10² cfu/g. diverse bacterial isolates were identified as histamine-forming bacteria. amongst them, proteus spp. with the highest abundance in samples contributed 24.5% followed by clostridium perfringens (22.5%), klebsiella spp. (15.0%), enterobacter spp. (11.5%) and the other isolates (26.5%). in comparison with usfda standard, the amount of histamine in 22.2 and 42.2% of the examined samples were 20- 50ppm, and >50ppm, respectively. therefore, there are seafood safety risks in the current harvesting and post harvesting methods used in skipjack industry and proper preventional methods for histamine formation are recommended