GROWTH DYNAMICS OF INDIGENOUS MICROBIAL POPULATIONS ON VEGETABLES AFTER DECONTAMINATION AND DURING REFRIGERATED STORAGE

Abstract

To ensure microbiological stability and safety in minimally processed (MP) salad vegetables, it is essential to consider the microbiology of this produce during cultivation and harvesting, and the potential changes to this microbiology through preparation, distribution and storage. This study takes two salad vegetables (lettuce and white cabbage) and, having enumerated a range of different physiological groups of microorganisms present on unwashed produce, determines the impact on each microbial group of applying a decontamination step in the preparation protocol. The disinfectant used was sodium dichloroisocyanurate. Decontamination reduced the total microbial load significantly on both vegetables. The levels of different microbial groups enumerated differed significantly between vegetables. All the microbial populations were reduced, but the biocidal effect of chlorine treatment varied with vegetable type. Reduction of the levels of lactic acid bacteria and aerobic psychrotrophs on cabbage was only achieved with inclusion of the decontamination step, and this effect, in general, did not last more than 3 days. Decontamination significantly reduced the levels of coliforms, and although the levels increased during refrigerated storage, they did not exceed initial levels found on unwashed produce. In addition, the levels found on treated cabbage remained lower than produce washed with water only.