Couvert Olivier, Guégan Stéphanie, Hézard Bernard, Huchet Véronique, Lintz Adrienne, Thuault Dominique, Stahl Valérie
Université de Brest, EA3882, Laboratoire Universitaire de Biodiversité et Ecologie Microbienne, UMT14.01 SPORE-RISK, 6 rue de l'Université, F-29334 Quimper, France.
Université de Brest, EA3882, Laboratoire Universitaire de Biodiversité et Ecologie Microbienne, UMT14.01 SPORE-RISK, 6 rue de l'Université, F-29334 Quimper, France.
Food Microbiol. 2017 Dec;68:89-96. doi: 10.1016/j.fm.2017.07.003. Epub 2017 Jul 7.
The effect of carbon dioxide, temperature, and pH on growth of Listeria monocytogenes and Pseudomonas fluorescens was studied, following a protocol to monitor microbial growth under a constant gas composition. In this way, the CO dissolution didn't modify the partial pressures in the gas phase. Growth curves were acquired at different temperatures (8, 12, 22 and 37 °C), pH (5.5 and 7) and CO concentration in the gas phase (0, 20, 40, 60, 80, 100% of the atmospheric pressure, and over 1 bar). These three factors greatly influenced the growth rate of L. monocytogenes and P. fluorescens, and significant interactions have been observed between the carbon dioxide and the temperature effects. Results showed no significant effect of the CO concentration at 37 °C, which may be attributed to low CO2 solubility at high temperature. An inhibitory effect of CO appeared at lower temperatures (8 and 12 °C). Regardless of the temperature, the gaseous CO is sparingly soluble at acid pH. However, the CO inhibition was not significantly different between pH 5.5 and pH 7. Considering the pKa of the carbonic acid, these results showed the dissolved carbon under HCO form didn't affect the bacterial inhibition. Finally, a global model was proposed to estimate the growth rate vs. CO concentration in the aqueous phase. This dissolved concentration is calculated according to the physical equations related to the CO equilibriums, involving temperature and pH interactions. This developed model is a new tool available to manage the food safety of MAP.
按照监测恒定气体组成条件下微生物生长的方案，研究了二氧化碳、温度和pH值对单核细胞增生李斯特菌和荧光假单胞菌生长的影响。通过这种方式，二氧化碳的溶解并未改变气相中的分压。在不同温度（8、12、22和37℃）、pH值（5.5和7）以及气相中二氧化碳浓度（0、20、40、60、80、100%大气压以及超过1巴）条件下获取生长曲线。这三个因素极大地影响了单核细胞增生李斯特菌和荧光假单胞菌的生长速率，并且观察到二氧化碳和温度效应之间存在显著的相互作用。结果表明，在37℃时二氧化碳浓度没有显著影响，这可能归因于高温下二氧化碳的低溶解度。在较低温度（8和12℃）下，二氧化碳出现抑制作用。无论温度如何，气态二氧化碳在酸性pH值下的溶解度都很低。然而，在pH 5.5和pH 7之间，二氧化碳的抑制作用没有显著差异。考虑到碳酸的pKa，这些结果表明以HCO形式存在的溶解碳不会影响细菌抑制作用。最后，提出了一个全局模型来估计水相中生长速率与二氧化碳浓度的关系。该溶解浓度是根据与二氧化碳平衡相关的物理方程计算得出的，涉及温度和pH值的相互作用。这个开发的模型是一种可用于管理气调包装食品安全的新工具。
