Abstract: The aim of this work was to investigate the bactericidal efficacy of dielectric barrier discharge atmospheric cold plasma (DBD-ACP) and its effect on the histamine content of mackerel (Pneumatophorus japonicus). Direct and indirect processing modes were adopted and their anti-microbial effects were compared based on the variations of total variable counts (TVC) in the fish. The voltage and treatment time were optimized using response surface methodology (RSM) combined with central composite design. Under optimized conditions, the effect of DBD-ACP treatment on the changes in histamine contents and histamine-producing microorganisms such as Pseudomonas, Enterobacter, and Vibrio during storage were evaluated. The results indicated that direct DBD-ACP treatment was more effective in the inactivation of microorganisms, which resulted in a 35.88% decrease in TVC, compared with indirect treatment. The optimal conditions were found to be 71.5 s treatment at a voltage of 59.9 kV. Under these conditions, TVC decreased to 1.83(lg(CFU/g)), which is in good agreement with the predictive value (1.86(lg(CFU/g))), suggesting that the proposed model could fit the experimental data well. During a 14-day period of storage, Distinctly slower growth rates were observed for Pseudomonas, Enterobacter and Vibrio in DBD-ACP treated samples. On the 8th day, the counts of Pseudomonas, Enterobacter and Vibrio decreased by 25.89%, 46.23% and 45.23%, respectively, compared to those of control groups. Meanwhile, a reduced rate of increase in histamine content was determined for DBD-ACP treated group, whose histamine content was measured to be 72.34 mg/100 g on the 14th day, lower than the national standard limit.

Key words: mackerel, atmospheric cold plasma, response surface methodology, bacterial variable count, histamine content