Lesson 5 - Fermentation and Beer Flavour SAQ

1. *Answer BOTH parts of this question, where necessary using diagrams:

a)    Describe the pathways which give rise to higher alcohols in beer and how their activities relate to wort composition.

b)    Discuss possible reasons why yeast cells synthesise higher alcohols.

2. **Answer BOTH parts of this question:

a)    What contribution do ATF genes in yeast make to beer flavour?

b)    Discuss the relationship between oxygen and the activity of the ATF genes.

3. **Describe three ways in which yeast can have an adverse effect on beer flavour and quality.

4. ***Your brewery is developing a new beer. Your role in the team is to develop a suitable fermentation regime. It is intended that the beer will be low carbohydrate and made by an intensive process. For this reason, it will use a combination of very high gravity brewing, high refined maize starch adjunct levels, and supplementation with an amyloglucosidase enzyme.

Initial trials indicate that fermentation cycles are much longer than planned for. The major problem is a very extended VDK stand time.

Fermentation vessels have a capacity of 6,000 hL, have a fill time of 18 hours, and require six batches of wort.

Discuss the likely causes of the problem and identify some measures you might consider taking to shorten fermentation cycle times.

5. **You have set up a brewery in a new location. Your analyses of the local water indicate that the content of sulphate is 150 mg/L. You do not have access to a water purification plant. You intend to brew pale lager beers using worts with a relatively low content of malted barley and high proportion of sugar adjunct. What effects might this combination of circumstances have on yeast sulphur metabolism during fermentation and on beer flavour? What steps might you take in response to the water analysis?