Influence of dissolved carbon dioxide on the growth of spoilage bacteria

Growth of bacteria is, for most strains, influenced by CO2 in the atmospher e. The effect of the concentration of dissolved CO2 ([CO2](diss) in mg/L) w as quantified for different Gram-negative (Pseudomonas fluorescens, Photoba cterium phosphoreum, Shewanella putrefaciens, Aeromonas hydrophila) and Gra m-positive (Lactobacillus sake. Brochothrix thermosphacta, Bacillus circula ns) spoilage bacteria at 7 degreesC. A linear relationship between [CO2](di ss) 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 pa rameters (lambda as well as mu (max)) of Gram-negative bacteria were more i nfluenced by [CO2](diss) in comparison to the growth parameters of Cram-pos itive bacteria. When CO2 is inserted in a food package, it will begin to dissolve in the wa ter phase of the food. The dissolving rate of CO2 was determined for gas pa ckaged 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, respe ctively 78 % and 87 % of the CO2 dissolved at equilibrium was already disso lved 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 volu me 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 v olume ratio was demonstrated as [CO2](diss) increased significantly (P < 0. 001) with increasing gas/product volume ratio (G/P). In average, an increas e of 42 % of [CO2](diss) was achieved when the G/P was increased from 1/1 t o 2/1. (C) 2000 Academic Press.