کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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6393707 | 1330455 | 2012 | 6 صفحه PDF | دانلود رایگان |
The objective of this study was to investigate the effect of nisin alone and in combination with heat (63 °C/5 min) on the inactivation of Listeria innocua in white cheese. Nisin was added at different concentrations (500, 1000, and 1500 IU mlâ1) to pasteurized milk before curd formation. The curd was soaked for 24 h in 10% solution of brine containing ca 106 CFU mlâ1 of a cocktail mixture of three strains of L. innocua. Part of the nisin treated samples were heat treated at 63 °C/5 min. Total mesophilic count (TMC), L. innocua survivors and changes in the pH of white cheese were monitored each 2 d for a period of 12 d of storage at 4 or 10 °C. Nisin at 500 IU mlâ1 did not diminish TMC in white cheese compared to the control. The combination of heat and nisin (1000 or 1500 IU mlâ1) exhibited a bacteriostatic effect on TMC throughout the storage period at 4 or 10 °C. Nisin at 500 IU mlâ1 had a marginal inhibitory activity against L. innocua. However, nisin at 1000 and 1500 IU mlâ1l resulted in a more than 2 log10 reduction in L. innocua count and the effect was more prominent at 10 °C. In comparison, the combination of nisin (1000 or1500 IU mlâ1) and heat treatment exhibited a synergistic inhibitory activity against L. innocua, where a complete elimination of the organism was accrued after 6 and 8 d of storage at 10 and 4 °C. Therefore, nisin and heat combination could be used as a prudent hurdle to preclude the growth of Listeria in white cheese, especially under the condition of abused refrigeration conditions.
⺠Brined white cheese is a ready-to-eat food product that is vulnerable to colonization by pathogens such as L. monocytogenes. ⺠Heat treatment exhibited a synergistic inhibitory activity against L. innocua in brined white cheese. ⺠Nisin and heat combination has the potential to improve the safety of white brined cheese even under abused refrigeration conditions.
Journal: Food Control - Volume 23, Issue 1, January 2012, Pages 48-53