Diez-Gonzalez Francisco, Belina Daniel, Labuza Theodore P, Pal Amit
Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Avenue, St. Paul, Minnesota 55108, USA.
Int J Food Microbiol. 2007 Feb 15;113(3):277-83. doi: 10.1016/j.ijfoodmicro.2006.08.011. Epub 2006 Nov 30.
In the current study, temperature dependent growth of Listeria monocytogenes strain H7776, with an initial inoculum level of approximately 0.1 CFU/mL or g, was modeled based on "time to detect" (TTD) using the Arrhenius equation. The activation energies (E(a)) obtained from specific growth rate and lag phase duration in tryptic soy broth (TSB) and frankfurters were compared. At 4 degrees C, the TTD for L. monocytogenes was 217 h in TSB and 48 h in portions of frankfurters. The TTD decreased as temperature increased from 4 to 36 degrees C in both culture media and frankfurters, and this relationship was modeled using the Arrhenius equation. Based on this model, the E(a) values for the TTD in TSB and frankfurters averaged 22.7 and 18.7 kcal/mol, respectively, and were not significantly different (p<0.05). Linear regression was performed on the exponential part of the growth curve to evaluate specific growth rate constants at each temperature using the Monod model. The E(a) values were also calculated based on the specific growth rate and the lag phase of L. monocytogenes in TSB and frankfurters incubated in the same range of temperatures. The average E(a) values for the specific growth rates and the lag phase durations in TSB cultures were 19 and 21 kcal/mol, respectively. In frankfurters, the average E(a) values were slightly greater for both specific growth rate and lag phase duration (29 and 35 kcal/mol, respectively), but these values were not significantly different from the E(a) calculated for the TTD in each medium. These results indicate that the TTD concept can be used to develop and validate safety-based shelf life models.
在当前研究中，以初始接种水平约为0.1 CFU/mL或g的单核细胞增生李斯特菌H7776菌株为对象，基于“检测时间”（TTD），使用阿伦尼乌斯方程对其温度依赖性生长进行了建模。比较了从胰蛋白胨大豆肉汤（TSB）和法兰克福香肠中特定生长速率和延迟期持续时间获得的活化能（E(a)）。在4℃时，单核细胞增生李斯特菌在TSB中的TTD为217小时，在部分法兰克福香肠中的TTD为48小时。在两种培养基和法兰克福香肠中，随着温度从4℃升高到36℃，TTD均降低，并且使用阿伦尼乌斯方程对这种关系进行了建模。基于该模型，TSB和法兰克福香肠中TTD的E(a)值平均分别为22.7和18.7 kcal/mol，且无显著差异（p<0.05）。对生长曲线的指数部分进行线性回归，以使用莫诺德模型评估每个温度下的特定生长速率常数。还根据在相同温度范围内培养的TSB和法兰克福香肠中单核细胞增生李斯特菌的特定生长速率和延迟期计算了E(a)值。TSB培养物中特定生长速率和延迟期持续时间的平均E(a)值分别为19和21 kcal/mol。在法兰克福香肠中，特定生长速率和延迟期持续时间的平均E(a)值略高（分别为29和35 kcal/mol），但这些值与每种培养基中TTD计算的E(a)值无显著差异。这些结果表明，TTD概念可用于开发和验证基于安全性的货架期模型。
