Changes in Amine Forming Bacteria and Histamine in Yellowfin Tuna (Thunnus albacares) Through the Smoking Process

The presence of amine forming bacteria and histamine formation in yellowfin tuna (Thunnus albacares) through the hot smoking process was investigated at five different stages of processing. The amine forming bacteria in the raw tuna were very low and were detected in higher proportion (48%) in hot blanched tuna. They survived to a certain extent during the smoking process (7-18%) and were totally absent in the final product because of low moisture (14%) and aw (0.86). The predominant amine forming bacteria identified were Micrococcus, Alcaligenes and Corynebacterium. The histamine level in the raw tuna was very low, which increased gradually through the process and reached a maximum of 12 ppm, which is well below the hazardous limit of 50 ppm prescribed by the USFDA. The result implies that a delay in hot blanching and smoking stage of processing could definitely contribute to the amine formation because of the presence of potential amine forming bacteria even if the initial bacteriological quality of tuna is good.