Food Science & Technology Programme, Department of Chemistry, National University of Singapore, Singapore 117543, Singapore.
Food Microbiol. 2012 Jun;30(2):448-52. doi: 10.1016/j.fm.2011.12.023. Epub 2012 Jan 3.
The aim of the present study was to determine the survival of Salmonella Typhimurium adapted with sodium lactate (NaL), potassium lactate/sodium acetate mixture (KL/NaA) or sodium acetate (NaA) in simulated gastric fluid (SGF) and during heat treatment. NaL-, KL/NaA- and NaA-adapted cells were prepared by incubating in tryptic soy broth (TSB) containing these salts at 5, 5 and 3% (w/v) concentration levels, respectively, for 24 h at 37 °C. The Baranyi model was used to compare the growth kinetic parameters of adapted cells. The acid and heat resistance of adapted cells were determined by incubating in SGF (pH 2.04) at 37 °C and in TSB at 55.8, 57.8 and 59.8 °C, respectively. Adapted cells had significantly (P < 0.05) longer lag phase duration (LPD) and slower maximum growth rate (MGR) than non-adapted cells. The acid resistance of KL/NaA-adapted cells was not significantly (P > 0.05) different from that of non-adapted cells. NaL-adapted cells were more susceptible to the low pH environment, whereas NaA-adapted cells showed enhanced acid resistance compared to non-adapted and other adapted cells. Unlike acid resistance, both NaL- and NaA-adapted cells showed enhanced heat resistance with increased D-values, regardless of treatment temperatures. Thus, this study indicates that adaptation of S. Typhimurium to 5% NaL or 3% NaA could enhance their ability to survive thermal processes or in the human stomach, possibly increasing the risk of Salmonella outbreaks.
本研究旨在确定经乳酸钠（NaL）、乳酸钾/乙酸钠混合物（KL/NaA）或乙酸钠（NaA）适应的鼠伤寒沙门氏菌在模拟胃液（SGF）和热处理过程中的存活情况。通过在含有这些盐的胰蛋白酶大豆肉汤（TSB）中分别于 5、5 和 3%（w/v）浓度水平下于 37°C 孵育 24 小时来制备 NaL、KL/NaA 和 NaA 适应的细胞。使用 Baranyi 模型比较适应细胞的生长动力学参数。通过在 SGF（pH 2.04）中于 37°C 和在 TSB 中于 55.8、57.8 和 59.8°C 下孵育来确定适应细胞的酸和耐热性。适应细胞的延迟期（LPD）明显长（P < 0.05），最大生长率（MGR）较慢。KL/NaA 适应细胞的耐酸性与非适应细胞无明显差异（P > 0.05）。NaL 适应细胞对低 pH 环境更敏感，而 NaA 适应细胞与非适应和其他适应细胞相比表现出增强的耐酸性。与耐酸性不同，无论处理温度如何，NaL 和 NaA 适应细胞均表现出增强的耐热性，D 值增加。因此，本研究表明，鼠伤寒沙门氏菌对 5% NaL 或 3% NaA 的适应可能会增强其在热加工过程或在人体胃中存活的能力，从而可能增加沙门氏菌爆发的风险。
