If microorganisms survive the heat treatment, then either the pasteuriser had an error, or its settings were wrong – or there were heat resistant microorganisms present which are common on fruit and plants. These are including typical spore producing bacteria as Bacillus species or Clostridia, but also heat resistant molds as some Penicillius species, Byssochlamys, Neosartorya, or Talaromyces. Through heat treatment usually the vegetative forms are killed, but the spores survive. And those are awakened by the impact of heat, they germinate and further proliferate, producing spoilage in the finished product.
The detection of those microorganisms in raw materials and before heat treatment is difficult if vegetative cell material is not present in a detectable amount – the spores themselves are hardly detectable. In juice and soft drink production analysis, such procedures which start with a heat treatment of the sample before the actual analysis by enrichment begins are state-of-the-art: The spore germination is induced and after that their detection is possible.
Breweries which more and more are producing mixed drinks have to follow, for them today there are no established routine methods available. We combine our experiences from microbiology in fruit drinks with our knowledge from the brewery analytics and can support you both with quick analyses as well as in the planning and establishing of analysis procedures for your products in your own lab.