In this study, E. coli DH5a and L. plantarum BFE 5092 in Quarterstrength Ringer's solution (QSRS) were subjected to UV-C treatment in a device based on liquid flow in a helically arranged FEP tube. Since the genetic disposition, the development status of the cells and environmental factors can affect the resilience of microorganisms a substantial knowledge of the microbial characteristics of main spoilage microorganisms as well as the relevant parameters affecting their UV-C sensitivity is required in order to correctly design the pasteurization process. In this study, the growth temperature
clearly affected the UV-C sensitivity of E. coli DH5a cells. However, no considerably difference in UV-C sensitivity could be observed for L. plantarum BFE 5092 incubated at different temperatures. In addition, L. plantarum BFE 5092, being more sensitive in stationary phase, was in general more resistant to UV-C in QSRS than E. coli DH5a. However, no effect of the initial pH of the growth
media and the several process temperatures and pH applied were detected. The results obtained in this study, which concern the microbial characteristics as well as the parameters influencing the microbial homeostasis and their effect on UV-C inactivation showed clearly that an extrapolation to other species is impossible and suggest that the effects of environmental factors (e.g. storage condition) on the microbial sensitivity should be included into the process design for the UV-C treatment of liquid foods. This may mean that storage and process temperatures before and during UVC treatment of food shall be given a special consideration and may be measured continuously or even controlled.
In this study, E. coli DH5a and L. plantarum BFE 5092 in Quarterstrength Ringer's solution (QSRS) were subjected to UV-C treatment in a device based on liquid flow in a helically arranged FEP tube. Since the genetic disposition, the development status of the cells and environmental factors can affect the resilience of microorganisms a substantial knowledge of the microbial characteristics of main spoilage microorganisms as well as the relevant parameters affecting their UV-C sensitivity is required in order to correctly design the pasteurization process. In this study, the growth temperatureclearly affected the UV-C sensitivity of E. coli DH5a cells. However, no considerably difference in UV-C sensitivity could be observed for L. plantarum BFE 5092 incubated at different temperatures. In addition, L. plantarum BFE 5092, being more sensitive in stationary phase, was in general more resistant to UV-C in QSRS than E. coli DH5a. However, no effect of the initial pH of the growthmedia and the several process temperatures and pH applied were detected. The results obtained in this study, which concern the microbial characteristics as well as the parameters influencing the microbial homeostasis and their effect on UV-C inactivation showed clearly that an extrapolation to other species is impossible and suggest that the effects of environmental factors (e.g. storage condition) on the microbial sensitivity should be included into the process design for the UV-C treatment of liquid foods. This may mean that storage and process temperatures before and during UVC treatment of food shall be given a special consideration and may be measured continuously or even controlled.
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