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.
Preface
The previous lesson reviewed the microorganisms capable of spoiling beer by producing off-flavours and haze instability. This lesson describes procedures, both traditional and rapid, for isolating, identifying, and quantifying these microorganisms. It also discusses factors in wort and beer that affect the ability of microorganisms to grow in different stages of the beer production process.
Detection and quantification of brewery contaminating organisms is not an easy task. They occur at low concentrations, often amongst yeast cells at a level of 1 per million yeast cells. In addition, sample size to beer volume is very low, for example 250 mL per 300,000 L (3,000 hL). We can make the sample more representative through continuous on-line sampling equipment, where a sample is taken automatically at a defined time interval. We can then concentrate the sample by vacuum filtration through a sterile membrane before we subject it to either traditional or more modern, rapid tests for detection and numeration.