Control of Listeria monocytogenes and spoilage bacteria on smoked salmon during storage at 5 ℃ after X-ray irradiation

摘要

In this study, smoked salmon fillets were artificially inoculated with Listeria monocytogenes (3.7 ± 0.2 log CFU g~(-1)) and treated with X-ray irradiation generated by a RS 2400 X-ray machine (Rad Source Technologies Inc.) using doses of 0.0,0.1,0.5,1.0, and 2.0 kGy. Unirradiated and irradiated samples were then stored at 5 ℃ for 35 days and tested for L. monocytogenes count after 0,5,10,15,20,25,30, and 35 days. Also, uninoculated-untreated and uninoculated-treated samples with the lowest and highest X-ray doses (0.1 and 2.0 kGy) were stored at 5 ℃ and examined for psychrotrophs and mesophiles counts after 0, 5,10,15, 20, 25, 30, and 35 days. The initial L. monocytogenes population (3.7 log CFU g~(-1) ) was significantly (p < 0.05) reduced to an undetectable level (<1.0 log CFU g~(-1)) by treatment with 1.0 kGy X-ray. Treatment with 0.1 kGy X-ray significantly reduced the initial psychrotrophs and mesophiles counts from 5.3 and 3.0 to 3.3 and 2.3, respectively. However, L monocytogenes, psychrotrophs and mesophiles counts were gradually increased during storage. Treatment with 2.0 kGy X-ray kept the L. monocytogenes population under detectable level until 35 days. Treatment with 2.0 kGy X-ray kept the mesophiles and psychrotrophs counts within the acceptable level until 35 days. These results revealed that treatment with X-ray irradiation can significantly reduce the risk of listeriosis and extend the shelf life of smoked salmon during storage at 5 ℃.