I am presently audting a mineral water bottling plant in China. all bottles are PET bottles and they have some infection despite a lot of 0,22 micron filters. They take a hugh amount of samples to try to be in control. The funny thing is that they only incubate sampels at 37 oC - not 20-22 oC. Does some of you have a well working microbiological sampling plan?
It should be mentioned that it is spring water from a natural souce.