Growth of Pseudomonas fluorescens in modified atmosphere packaged tofu

The objective was to study the growth of Pseudomonas in a food product (tofu) where it typically occurs as a spoilage organism, and when this product is stored under modified atmosphere.

A Pseudomonas strain was isolated from the endogenous microflora of tofu. Tofu was inoculated with the strain, packaged in different gas conditions (air, 100% N(2), 30% CO(2) /70% N(2) or 100% CO(2)) and stored under refrigerated conditions. Microbial loads and the headspace gas composition were monitored during storage.

The strain was capable of growing in atmospheres containing no or limited amounts of oxygen and increased amounts of carbon dioxide. Even when 100% CO(2) was used, growth could not be inhibited completely.

in contrast to the general characteristics of the genus Pseudomonas (strictly aerobic, highly sensitive to CO(2)), it should not be expected in the food industry that removing oxygen from the food package and increasing the carbon dioxide content, combined with cold storage, will easily avoid spoilage by Pseudomonas species. Guarantee of hygienic standards and combination of strategies with other microbial growth inhibiting measures should be implemented.