Effects of Freezing and Thawing Treatments on Natural Microflora, Inoculated Listeria monocytogenes and Campylobacter jejuni on Chicken Breast
2016
Choi, E.J., World Institute of Kimchi, Gwangju, Republic of Korea | Chung, Y.B., World Institute of Kimchi, Gwangju, Republic of Korea | Kim, J.S., National Academy of Agricultural Science, RDA, Wanju, Republic of Korea | Chun, H.H., World Institute of Kimchi, Gwangju, Republic of Korea
The effects of freezing and thawing conditions on microbiological quality and microstructure change of inoculated (Listeria monocytogenes and Campylobacter jejuni) and non-inoculated chicken breasts were investigated. Chicken breasts were frozen with air blast freezing (minus20, minus70, and minus150Celsius), ethanol (minus70Celsius) and liquid nitrogen (minus196Celsius) immersion freezing. There were no significant differences on the populations of L. monocytogenes inoculated with chicken breasts under different freezing conditions. However, air blast freezing (minus20Celsius) resulted in significant reductions for total aerobic bacteria and C. jejuni compared to the control and other freezing treatments. The frozen samples were thawed with (hot or cold) air blast, water immersion, and high pressure thawing at 4Celsius and 25Celsius. the populations of total aerobic bacteria, and yeast and mold in the frozen chicken breast increased by 5.78 and 4.05 log CFU/g after water immersion thawing (25Celsius) treatment. After five freeze-thaw cycles, the populations of total aerobic bacteria, yeast and mold, and C. jejuni were reduced by 0.29~1.40 log cycles, while there were no significant differences (P greater than 0.05) in the populations of L. monocytogenes depending on the freeze-thaw cycles. In addition, the histological examination of chicken breasts showed an increase in spacing between the muscle fiber and torn muscle fiber bundles as the number of freeze-thaw cycles increased. These results indicate that freezing and thawing processes could affect in the levels of microbial contamination and the histological change of chicken breasts.
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