Abstract

In this investigation, a series of samples were carried out to isolate and identify histamine-producing bacteria and analyze the histamine content for evaluation of harvesting and post harvesting procedures. The target fish was longtail tuna (Thunnus tonggoh), which 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 4.81 ± 0.26 and 4.66 ± 0.25 Log₁₀CFU/g, respectively. Diverse bacterial isolates were identified as histamine-forming bacteria. Amongst them, Clostridium perfringens with the highest abundance in samples contributed 24.4% followed by Proteusspp. (23.0%), Klebsiella spp. (13.9%), and Enterobacter spp. (11.1%). The examined samples of 20.0, 15.0 and 65.0% contained < 20, 20 to 50 and >50 ppm amount of histamine, respectively. Therefore, there are seafood safety risks in the current harvesting and post harvesting methods used in longtail tuna industry.

Key words: Longtail tuna, Thunnus tonggoh, histamine, bacteria, Oman Sea.