Effect of dissolved carbon dioxide and temperature on the growth of Lactobacillus sake in modified atmospheres.
Carbon dioxide is known to be the active gas in modified atmosphere packaging. However, only the dissolved part of the CO2 will be active in the inhibition of microorganisms. When the effect of a modified atmosphere on the growth of microorganisms is modeled, the amount of dissolved CO2 should be the parameter to evaluate the effect of CO2 in modified atmospheres. Lactobacillus sake was isolated from cooked ham, identified and was chosen as a representative organism for the spoilage of modified atmosphere packed cooked meat products. In a first step a suitable liquid simulation medium for cooked meat products was selected. The growth rate of L. sake was significantly higher in modified MRS than in cooked ham, while no significant difference was observed between the growth parameters of L. sake in modified BHI and in cooked ham. Careful evaluation of the applied simulation medium was shown to be essential before application to the development of predictive models for nutrient demanding microorganisms such as lactic acid bacteria. In a second step, the influence of dissolved CO2 and the storage temperature on the growth parameters of L. sake was modeled. Temperature was shown to have a major effect on the growth rate and lag phase of L. sake. Carbon dioxide negatively influenced the growth rate of L. sake. A negative, linear relationship was observed between the growth rate and the amount of dissolved carbon dioxide. Carbon dioxide was shown, however, to have no significant effect on the lag phase of L. sake. A significant interaction term between temperature and dissolved CO2 on the growth rate of L. sake was established.