Lesson 6 - Microorganism Detection and Control
This lesson covers the procedures available for detecting microorganisms in wort and beer. It compares traditional detection methods, which use solid and liquid media, with more modern, rapid methods. It then looks at microorganism entry points within the brewing process and discusses factors that inhibit or encourage their existence and proliferation.
Rapid Methods
Although rapid methods do offer quicker measurement, often the samples must be incubated in liquid medium in order to increase the sensitivity of the test. The methods requiring this pre-enrichment can be termed culture dependent whereas those not requiring enrichment are termed culture independent. There has not yet been mainstream adoption of these techniques, although this is changing rapidly. Capital costs for equipment are expensive and, while sensitivity of some tests is excellent, it is not always possible to tell if identified organisms are alive or dead.
The culture dependent and independent methods each have their advantages and disadvantages, and they can complement each other. Culturing takes time and may be tricky, but this leaves an opportunity for further characterisation. Culture independent techniques, on the other hand, are fast and do not rely on a cultivated population.
Rapid tests can be classified into those using:
- Physical methods
- Biochemical methods
- Molecular methods
Molecular methods are currently the new frontier in microbiology and will eventually supersede traditional methods.
With all these test available to us, we might wonder just how much detail the brewer really needs to know about the contaminants present.
Certainly a brewer would like to know the genus of the contaminant, but they would probably not be that interested in the species. In terms of classification order, the genus ranks below the family but above the species. Understanding the genus is sufficient to understand the biochemical and physical effects that the invading microorganism will have on beer. Hence the development of easy-to-use rapid kit methods on the market today.