The influence of acid stress on the growth of Listeria monocytogenes and Escherichia coli O157:H7 on cooked ham

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• 作者：Cheng-An Hwang ; Shiowshuh Sheen ; Vijay Juneja ; Chin-Fa Hwang ; Tzu-Chiao Yin ; Nai-Yu Chang
• 关键词：Listeria monocytogenes ; Escherichia coli O157 ; H7 ; Acid stress ; Meat
• 刊名：Food Control
• 出版年：March, 2014
• 年：2014
• 卷：37
• 期：Complete
• 页码：245-250
• 全文大小：354 K

文摘

Acid solutions are increasingly being used for decontaminating meat surfaces. On the surfaces of acid-treated meat, the population of microorganism is reduced due to the low pH of acids, and the subsequent growth of the microorganism is reduced due to the residual acids on meat surfaces. Microbial cells on meat surfaces subjected to acid treatments may cross-contaminate untreated meat surfaces, e.g., microorganisms on the surfaces of acid-treated cooked ham cross contaminate the untreated surfaces during slicing. The objective of this study was to examine this scenario in determining the subsequent growth of acid-treated Listeria monocytogenes and Escherichia coli O157:H7 on the surfaces of untreated meat. Cells of multiple-strain L.聽monocytogenes or E.聽coli O157:H7 were exposed to HCl solutions of pH 3, 4, or 5 and deionized water at room temperature for 24聽h. The acid or deionized water-treated cells were inoculated separately onto cooked ham. Samples inoculated with L.聽monocytogenes were stored at 4 and 8聽掳C and samples inoculated with E.聽coli O157:H7 were stored at 10 and 12聽掳C. Populations of the pathogens on ham were enumerated during storage, and the lag phase durations (LPD, h) and growth rates (GR, log CFU/h) of the pathogens were determined. The populations of L.聽monocytogenes and E.聽coli O157:H7 in pH 5, 4, and 3 solutions were 1.2-3.1 and 0.6-2.4 log聽CFU/ml, respectively, lower than those in deionized water, indicating an increased acid stress on both microorganisms at lower pHs. L.聽monocytogenes subjected to pH 3 and pH 4 stresses and E.聽coli O157:H7 subjected to pH 3 stress exhibited significantly (p聽<聽0.05) extended LPDs and reduced GRs on cooked ham. The growth of L.聽monocytogenes on ham was more readily reduced by acid stress than that of E.聽coli O157:H7. This study showed that acid treatments reduced the viability of L.聽monocytogenes and E.聽coli O157:H7and the acid stress reduced their subsequent growth ability on untreated ham. Therefore, cross-contamination of L.聽monocytogenes or E.聽coli O157:H7 cells from acid-treated meat surfaces onto untreated meat surfaces may not impose increased risk to the product.