Lesson 6 - Yeast Propagation

This lesson introduced us to the subject of yeast propagation. We have explored what yeast propagation is and why it is needed, while considering the definition of propagation and the criteria for its success. We have looked at the concept of the master culture, and how these can be stored safely, as well as how to recover master strains from storage and to generate a new working culture at laboratory scale. Yeast propagation is a big topic and we have covered many aspects of it in this lesson.

You should now be able to:

1. Understand why most brewers choose to use pure yeast cultures.

2. Explain why some brewers choose to use mixed cultures.

3. Explain the practice of serial re-pitching and why this introduces a need for propagation.

4. Define propagation and outline its component parts.

5. List, with an assessment of strengths and weaknesses, the methods used to maintain yeast cultures.

6. Describe a typical protocol for recovering yeast cultures from storage and propagating a new culture in the laboratory.

7. Describe the process of yeast propagation in the brewery together with a critical discussion of the strengths and weaknesses of traditional methods.

8. Demonstrate an understanding of the role of oxygen in yeast propagation and discuss the consequences on yeast physiology of using wort as the growth medium.

9. Describe the underlying design features of continuously aerobic yeast propagation plant.

10. Understand the likely impact of the physiological condition of newly propagated yeast on subsequent performance in fermentation.

A self-assessment lesson now follows, which will allow you to assess the level to which you have attained the outcomes of this lesson.