Miller Fátima A, Ramos Bárbara, Gil Maria M, Brandão Teresa R S, Teixeira Paula, Silva Cristina L M
CBQF, Universidade Católica Portuguesa, Rua Dr. António Bernardino de Almeida, Porto, Portugal.
Int J Food Microbiol. 2009 Jul 31;133(1-2):121-8. doi: 10.1016/j.ijfoodmicro.2009.05.007. Epub 2009 May 9.
Acidification of foods with organic acids, either by fermentation or by intentional addition, is an important and common mechanism for controlling foodborne pathogens in a diversity of food products. The objective of this work was to study thermal inactivation of Listeria innocua, an acid tolerant microorganism, at 52.5, 60.0 and 65.0 degrees C, at different pH values (4.5, 6.0 and 7.5), using three types of acid (lactic, acetic and hydrochloric) and three different plating media (Tryptic Soy Agar with 0.6% yeast extract-TSAYE; TSAYE plus 5% NaCl-TSAYE+5%NaCl; and Palcam Agar with selective supplement-Palcam Agar), according to a 3(4) factorial experimental design. Survival data experimentally obtained were fitted with a Gompertz-inspired model and kinetic parameters (shoulder, maximum inactivation rate-k(max), and tail) were estimated for all conditions considered. The influence of temperature, pH, type of acid and enumeration media on kinetic parameters was assessed. Results showed that, with the exception of the type of acid, all the remaining factors and their combinations significantly affected the shoulder period and k(max). In relation to tail, temperature and recovery media were the affectable factors. It was concluded that the survival of this bacteria is higher when combining low temperature with neutral pH, and when TSAYE is the enumeration medium. Bigelow-inspired models were successfully developed and describe accurately the temperature and pH effects on the kinetic parameters.
通过发酵或有意添加有机酸对食品进行酸化，是控制多种食品中食源性病原体的一种重要且常见的机制。本研究的目的是，根据3(4)析因实验设计，研究无害李斯特菌（一种耐酸微生物）在52.5、60.0和65.0摄氏度、不同pH值（4.5、6.0和7.5）条件下，使用三种类型的酸（乳酸、乙酸和盐酸）以及三种不同的平板计数培养基（含0.6%酵母提取物的胰蛋白胨大豆琼脂 - TSAYE；TSAYE加5%氯化钠 - TSAYE + 5%NaCl；以及含选择性添加剂的Palcam琼脂 - Palcam Agar）时的热失活情况。将实验获得的存活数据与一个受Gompertz启发的模型进行拟合，并估算所有考虑条件下的动力学参数（滞后期、最大失活速率 - k(max)和拖尾期）。评估了温度、pH值、酸的类型和计数培养基对动力学参数的影响。结果表明，除酸的类型外，所有其他因素及其组合均对滞后期和k(max)有显著影响。关于拖尾期，温度和复苏培养基是可影响的因素。得出的结论是，当低温与中性pH值相结合，且以TSAYE作为计数培养基时，这种细菌的存活率更高。成功开发了受Bigelow启发的模型，该模型准确描述了温度和pH值对动力学参数的影响。
