Influence of dissolved carbon dioxide on the growth of spoilage bacteria

Growth of bacteria is, for most strains, influenced by CO2 in the atmosphere. The effect of the concentration of dissolved CO2 ([CO2](diss) in mg/L) was quantified for different Gram-negative (Pseudomonas fluorescens, Photobacterium phosphoreum, Shewanella putrefaciens, Aeromonas hydrophila) and Gram-positive (Lactobacillus sake. Brochothrix thermosphacta, Bacillus circulans) spoilage bacteria at 7 degreesC. A linear relationship between [CO2](diss) and the maximum specific growth rate mu (max) as well as between [CO2](diss) and the inverse of the lag phase lambda was established The growth parameters (lambda as well as mu (max)) of Gram-negative bacteria were more influenced by [CO2](diss) in comparison to the growth parameters of Cram-positive bacteria. When CO2 is inserted in a food package, it will begin to dissolve in the water phase of the food. The dissolving rate of CO2 was determined for gas packaged cooked ham at 7 degreesC. CO2 showed a high dissolving rate as, for an initial CO2 concentration in the headspace of 40 and 80 mL/100 mL, respectively 78 % and 87 % of the CO2 dissolved at equilibrium was already dissolved after 60 min. The [CO2](diss) at 7 degreesC in the aqueous phase of several food products, packaged in a realistic gas mixture and at two different gas/product volume ratios (1/1 and 2/1), was determined as well. The levels of [CO2](diss) varies between 152 and 898 mg/L while the average ratio of [CO2](diss) (mg/L) over the initial CO2 concentration (mL/100 mL) in the headspace amounted ro 8.98 +/- 1.41 ([mL/L]/[mL/100 mL]). The importance of the gas/product volume ratio was demonstrated as [CO2](diss) increased significantly (P < 0.001) with increasing gas/product volume ratio (G/P). In average, an increase of 42 % of [CO2](diss) was achieved when the G/P was increased from 1/1 to 2/1. (C) 2000 Academic Press.