Effect of gamma-ray and microwave treatment on the shelf-life of beef products stored at 5°C

The effect of gamma radiation and microwave treatments of different beef products were investigated with respect to survival and growth of bacteria, shelf-life, chemical content and sensory quality. When beef samples with an initial bacterial count of 4.9×106 CFU/g were exposed to gamma rays at a dose level of 5.0 kGy, counts of bacteria were reduced by 2–3 log cycles and when heated in a microwave oven, bacterial counts were reduced by 1 log cycle in 20 s and by 2 log cycles in 30 s exposure. Untreated samples had a shelf-life of less than 7 days, whereas samples that were irradiated at a dose level of 3 kGy, then heated in microwave oven for 20 s had a shelf-life of at least 2 weeks at 5°C. Gamma-rays treatment had a very little effect on the odor and flavor of the pretreated sample. The combined treatment shows either no change or loss of thiamine levels and free fatty acids but increased the peroxide values during storage at 5°C. It was concluded that the combined treatment of gamma ray and microwave at lower levels can greatly enhance the microbial safety of beef products