Lesson 5 - Fermentation and Beer Flavour SAQ
This lesson enables you to test yourself on the material covered in the Fermentation and Beer Flavour lesson and determine to what level you have attained the outcomes.
Suggested Response - Q3
**Describe three ways in which yeast can have an adverse effect on beer flavour and quality.
Response:
Yeast can have an indirect and adverse effect on beer flavour where fermentation conditions cause excessive stress or cell death.
In this situation, the dead cells lyse and release their contents into the green beer. The contents of the dead cells include proteases and these will degrade beer foam proteins with a negative effect on beer head-forming ability.
The release of dead cell contents causes an increase in beer pH, which lowers its resistance to microbial spoilage.
Some of the contents of dead cells produce characteristic off-flavours, usually referred to as ‘yeast-bitten’.
There is another less obvious negative effect. During fermentation a proportion of hop alpha acids bind non-specifically to yeast cell walls. Hopping rates have to include an allowance to account for this loss.