Histamine risk assessment in Scombridae fish across processing forms and distribution channels: a case study from Nghe An Province, Vietnam

sp.), in Nghe An Province, where the highest frequency of recent outbreaks was recorded. Histamine concentrations were determined by LC-MS/MS in 540 samples collected from wet markets/fish landing ports, supermarkets/cold storage facilities, and food service establishments. Overall, histamine concentrations were generally low across the three Scombridae species and distribution channels. The highest concentrations were most often observed in samples from wet markets/fish landing ports, with maximum levels of 63.9, 109, and 411 mg/kg recorded for Spanish mackerel, fresh Indian mackerel, and bullet tuna, respectively. Grilled Indian mackerel from supermarkets was identified as a product category of potential concern, with a higher proportion of samples exceeding 15 mg/kg and a maximum histamine concentration of 319 mg/kg, possibly reflecting variation in raw material quality before heat treatment. As expected, the estimated risks of experiencing histamine poisoning symptoms were relatively low for Spanish mackerel and bullet tuna, at 4-7 cases per million servings and 6-14 cases per 10 million servings, respectively. In contrast, grilled Indian mackerel products had the highest estimated risk, with a probability of 3-6 cases per 10,000 servings. These findings highlight the need to strengthen surveillance of grilled Indian mackerel products and to conduct further studies to identify critical stages in the processing and distribution chains where histamine formation may occur.