US Department of Agriculture, ARS, Food Safety Intervention Technologies Research Unit, Eastern Regional Research Center, Wyndmoor, PA 19038-8551, USA.
Food Microbiol. 2011 Feb;28(1):67-75. doi: 10.1016/j.fm.2010.08.008. Epub 2010 Aug 20.
The goal of this study was to develop a general model of inactivation of salmonellae in commercial liquid egg yolk for temperatures ranging from 58°C to 66°C by studying the inactivation kinetics of Salmonella in liquid egg yolk. Heat-resistant salmonellae (three serovars of Enteritidis [two of phage type 8 and one PT 13] and one Oranienburg) were grown to stationary phase in Tryptic Soy Broth and concentrated 10-fold by centrifugation. Each inoculum was added to liquid egg yolk and mixed thoroughly, resulting in a final population of ca. 7 log CFU/ml egg yolk. Inoculated yolk was injected into sterile glass capillary tubes, flame-sealed and heated in a water bath at 58, 60, 62, 64, and 66°C. Capillary tubes were ethanol sanitized, rinsed, and contents were extracted. Yolk was diluted, surface plated onto Tryptic Soy Agar+0.1% sodium pyruvate and 50 μg/ml nalidixic acid and incubated at 37°C for 24 h before colonies were enumerated. Decimal reduction values were calculated from survivor curves with a minimum inactivation of 6 log CFU/ml at each temperature. Survival curves (except for 66°C) featured initial lag periods before first order linear inactivation. Estimated asymptotic D-values were 1.83 min at 58°C, 0.69 min at 60°C, 0.26 min at 62°C, 0.096 min at 64°C and 0.036 min at 66°C. The estimate of the asymptotic z-value was ca. 4.7°C with standard error of 0.07°C. A linear relationship between the log(10) of the lag times and temperature was observed. A general kinetic model of inactivation was developed. The results of the study provide information that can be used by processors to aid in producing safe pasteurized egg yolk products and for satisfying pasteurization performance standards and developing industry guidance.
本研究的目的是通过研究液态蛋黄中沙门氏菌的失活动力学，为 58°C 至 66°C 范围内的商业液态蛋黄中沙门氏菌的失活建立一个通用模型。耐热沙门氏菌（三种肠炎血清型[两种噬菌体型 8 和一种 PT 13]和一种奥兰尼堡）在胰蛋白酶大豆肉汤中生长至静止期，然后通过离心浓缩 10 倍。将每个接种物添加到液态蛋黄中并充分混合，最终蛋黄中的种群数约为 7 log CFU/ml。将接种的蛋黄注入无菌玻璃毛细管中，火焰密封，在水浴中于 58、60、62、64 和 66°C 加热。毛细管用乙醇消毒，冲洗，并提取内容物。蛋黄稀释后，表面接种于胰蛋白酶大豆琼脂+0.1%丙酮酸钠和 50 μg/ml 萘啶酸，在 37°C 孵育 24 小时，然后计数菌落。从幸存者曲线上计算十进制减少值，每个温度下至少有 6 log CFU/ml 的失活。除 66°C 外，生存曲线（除 66°C 外）在一级线性失活之前均有初始滞后期。估计的渐近 D 值在 58°C 时为 1.83 分钟，在 60°C 时为 0.69 分钟，在 62°C 时为 0.26 分钟，在 64°C 时为 0.096 分钟，在 66°C 时为 0.036 分钟。渐近 z 值的估计值约为 4.7°C，标准误差为 0.07°C。观察到滞后时间与温度之间的对数（10）的线性关系。建立了一个通用的失活动力学模型。研究结果为加工商提供了可用于生产安全巴氏杀菌蛋黄产品的信息，并满足巴氏杀菌性能标准和制定行业指南。
