Different Methods to Control and Eliminate the Microorganisms on the Surface of Sprouts
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Abstract:
This research started with five different treatments of sprouts i.e. water washing, irradiation, cold and heat shocks, application of chlorine-containing disinfectant or cleaning agent with a labelled bactericidal component, to investigate in depth the changing trends of the microbial growth and decline and the population structure of microorganisms in the ready-to-eat vegetables under different treatments. The dynamic growth models for the total amount of microorganisms were then established. The changes in the abundance of microbial populations before and after the individual treatment were investigated by metagenomics, and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) was used to identify the dominant population after selective culture. The experimental results showed that the total number of microorganisms in the ready-to-eat sprouts remained constant at an order of magnitude (5-6 lg CFU/g). The treatments broke the balance of the microbial population structure, however, the total number of microorganisms would return to the previous stable level after a certain period of time. Among the different treatments, irradiation exhibited the most obvious influence. The methods capably of altering water activity (i.e. water washing, cold and heat shocks and cleaning agent with a labelled bactericidal component) seemed less effective causing quicker recovery of microbial amounts, with the effect on microorganisms slightly varying with the different labelled bactericidal component. It was concluded that the differences in the working mechanisms underlying the treatments accounted mainly for the changes in microbial population structure. In addition, the irradiation method could change the dominant population in the sprouts, Pseudomonas Sp. and Lactobacillus Sp , into Bacillus Sp. (with Bacillus cereus detected), which increased food poisoning risk with its consumption. That is, the most effective method of suppressing the microorganisms in the ready-to-eat vegetables is not necessarily the safest method. In the control of microorganisms in ready-to-eat fruits and vegetables, not only the reduction of the total microbial amount but also other factors related to the microecology of microorganisms must be considered.
