Annous B A, Kozempel M F
U.S. Department of Agriculture, Eastern Regional Research Center, Wyndmoor, Pennsylvania 19038, USA.
J Food Prot. 1998 May;61(5):578-81. doi: 10.4315/0362-028x-61.5.578.
Pediococcus sp. is a nonpathogenic heat-resistant spoilage organism that has been used as a test organism in milk pasteurization studies. These characteristics make this bacterium an attractive test organism to study the mode of bacterial thermal inactivation in a food pilot plant. We report here the effect of growth medium on the thermal D value of this organism in skim milk, whole liquid egg, 10% glucose solution, pineapple juice, apple juice, tomato juice, and water at 60 degrees C. Thermal inactivation was done in a submerged coil; D values were calculated from the linear portion of the survival curves by linear regression analysis. The range of D values of stationary-phase cells grown at 28 degrees C in tryptone glucose yeast extract (TGY) or tryptic soy broth (TSB) was 0.14 to 12.05 min in all heating menstrua tested. The TSB-grown cells exhibited the highest thermal resistance with skim milk and 10% glucose solution as the heating menstrua. Survival curves of the TGY-grown cells indicated the presence of a cell population heterogeneous in thermal resistance. The TSB-grown cells exhibited a cell population uniform in thermal resistance and with a lag time for thermal inactivation. When compared to TGY-grown cells, Pediococcus sp. grown in TSB showed a significant (P < 0.05) increase in D values by up to eightfold in all heating menstrua. Results from this study suggested that thermal inactivation of Pediococcus sp. was dependent on the growth medium and on the heating menstruum with respect to both pH and composition.
片球菌属是一种非致病性耐热腐败菌，已被用作牛奶巴氏杀菌研究中的试验菌。这些特性使这种细菌成为研究食品中试工厂细菌热灭活模式的理想试验菌。我们在此报告生长培养基对该菌在脱脂牛奶、全蛋液、10%葡萄糖溶液、菠萝汁、苹果汁、番茄汁和60℃水体系中的热D值的影响。热灭活在浸没式盘管中进行；通过线性回归分析从存活曲线的线性部分计算D值。在胰蛋白胨葡萄糖酵母提取物（TGY）或胰蛋白胨大豆肉汤（TSB）中于28℃培养的稳定期细胞，在所有测试的加热介质中的D值范围为0.14至12.05分钟。以脱脂牛奶和10%葡萄糖溶液作为加热介质时，在TSB中培养的细胞表现出最高的热抗性。TGY培养的细胞的存活曲线表明存在热抗性异质的细胞群体。TSB培养的细胞表现出热抗性均匀且有热灭活延迟期的细胞群体。与TGY培养的细胞相比，在TSB中培养的片球菌属在所有加热介质中的D值显著（P < 0.05）增加，最高可达八倍。本研究结果表明，片球菌属的热灭活取决于生长培养基以及加热介质的pH值和组成。
