In a brewery, positives are generally detected in enrichments. But from his experience the brewmaster knows that in enrichments some bacteria may grow up to detectable numbers more or less frequently, but there is no danger at any time for the product beer – the beer stays clean. Why?
In the closed container there are different conditions than in enrichment: There are barely no available nutrients in beer, there is no oxygen and usually storage is in a cool place.
In contrast, beer spoilers find an optimized supply of nutrients in enrichment, and they are incubated at convenient temperature. The aim is to bring all potentially present microorganisms to proliferation within a short time to be able to reliably detect them. Therefore, you can always expect – provided that the analysis covers a representative volume – a higher detection rate of contaminations in enrichments than in the finished beer.
The results from routine control in a brewery are used to maintain the optimal hygiene status and to prevent growth of problem bacteria even within the production process. But nevertheless, the real beer spoiling bacteria should always be differentiated because only this type of result gives you knowledge about the actual product risk.