Abstract
The fate of Listeria monocytogenes (IID 581, serotype 4b) was studied in various Japanese fishery products. Numbers of L.monocytogenes were reduced in all samples (“nishinhirikomi”, “ ika-shiohara” and “sake-izushi”) during maintenance at 5°C, 12°C and 25°C. In “nishin-kirikomi”, numbers of L. monocytogenes were gradually reduced at 5 and 12°C (reduction of 1.6log cfu/ml and 2.8 log cfu/ml, respectively), but were reduced only slightly for 7 days at 25°C. However, numbers of L. monocytogenes rapidly reduced to undetectable levels in “ika-shiokara” at all temperatures examined (5, 12 and 25°C). In“sake-izushi”, numbers of L.monocytogenes were reduced at all temperatures, but it survived 2.2 log cfu/ml after 28 days at 5°C.
The fate of L. monocytogenes was also evaluated in three kinds of “izushi”. It was shown that numbers of L. monocytogenes rapidly reduced in all samples examined, as the number of lactic acid bacteria (LAB) increased. Most of the LAB isolated from the three kinds of izushi were cocci. These results showed that inclusion of LAB in izushi resulted in the reduction of numbers of L. monocytogenes.
