RADIATION INACTIVATION OF SOME FOOD-BORNE PATHOGENS IN FISH AS INFLUENCED BY FAT LEVELS

The influence of low (0.39-1.1%), medium (4.25%) and high (7.1-32.5%) fat levels in fish on radiation inactivation of four food-borne pathog ens was investigated. Cells of Listeria monocytogenes 036, Yersinia en terocolitica F5692, Bacillus cereus and Salmonella typhimurium at loga rithmic phase were inoculated in 10% fish homogenates and subjected to gamma irradiation at ice temperature (0-1 degrees C) with doses rangi ng-from 0.05 to 0.8 kGy. The radiation survival curves oft. monocytoge nes and B. cereus were characterized by shoulders, while a tailing eff ect was depicted by cells of Y. enterocolitica and B, cereus. The D-10 values in kGy calculated on the exponential part of the curve ranged from 0.2 to 0.3, 0.15 to 0.25, 0.1 to 0.15 and 0.09 to 0.1 for L. mono cytogenes 036, B. ce, eus, Salm. typhimurium and Y. enterocolitica F56 92, respectively. This order (D-10) of radiation resistance of each or ganism was not affected by the fat content of the fish. Inoculated pac k studies carried out separately with each pathogen in fatty (Indian s ardine, 7.1%) and lean (Golden anchovy, 0.39%) fish showed no differen ce in their survival after exposure to 1 kGy and 3 kGy doses, which co rroborated the above observation. The practical significance of these results in the application of the technology is discussed.