Elimination of Listeria monocytogenes and changes in physical and sensory qualities of a prepared meal following gamma irradiation

The increase in demand for ready-to-eat foods and recent events involving L isteria contamination in such foods have indicated that processes which can enhance product safety are needed. This study was designed to investigate the effects of irradiation on a prepared meal contaminated with a known foo dborne pathogen, Listeria monocytogenes. The product consisting of Salisbury steak, gravy and mashed potatoes was co ntaminated with L. monocytogenes, irradiated at doses of 0.8, 2.9 and 5.7 k Gy, and stored at 4 degreesC for 3 weeks. Listeria was not recovered from a ny sample at any time point, even after selective enrichment, for product t reated at 5.7 kGy which represented a greater than a six-log cycle reductio n Treatment with 2.9 kGy reduced the pathogen by over five logs but treatme nt with 0.8 kGy was not very effective, only reducing counts by approximate ly one log in samples where Listeria survived, counts increased during refr igerated storage. Irradiation with 5.7 kGy also effectively eliminated the background aerobic and yeast and mold populations for the duration of the s tudy Lower doses have less of an effect on these populations. Instrumental measurements of texture and color revealed no effect of irradi ation dose. Furthermore, sensory tests revealed that the irradiated meals w ere no less acceptable than non-irradiated meals. It appears that irradiati on at 5.7 kGy is an effective means of improving safety and extending shelf -life without causing adverse effects on quality. (C) 2001 Academic Press.