Lesson 3 - Fermentation Principles SAQ
This lesson enables you to test yourself on the material covered in the Fermentation Principles lesson and determine to what level you have attained the outcomes.
Self-Assessment Questions
1. *Define the following terms:
a) Attenuation gravity
b) Wort fermentability
c) Original gravity
d) High gravity brewing
2. **Answer BOTH parts of this question:
a) Draw a labelled diagram showing the major phases in fermentation and briefly describe what is happening in each.
b) If a fermentation stops at an unexpectedly high gravity how would you test if the problem was related to wort composition or a failure in fermentation control?
3. **To what extent do each of the following variables influence how much yeast grows during fermentation?
a) Wort concentration
b) Wort oxygen concentration
c) Temperature
d) Pitching rate
4. **Answer both parts of this question:
a) A wort contains 180 g/L of extract. Using a simple mass balance, calculate the amount of ethanol per litre that would be produced if the wort was fully attenuated.
b) What could make the ethanol yield lower and how can you control this in the brewery?
5. **You have been asked to manage the introduction of high gravity brewing into your brewery. Current fermentations use malt wort with a gravity of 12 °P. For greater economy, the plan is to increase the gravity of the wort to 17 °P using a sugar adjunct largely made of maltose. At the same time, the fermentation temperature is being increased from the current 15 °C up to 18 °C. Assume the efficiency of fermentation is 88%.
a) How much additional ethanol (abv) would you expect the fermentation to generate? Assume the adjunct is pure maltose and use typical efficiency figures for fermentation. The molecular weights of maltose and ethanol are 342.3 and 46.1, respectively. The density of ethanol is 790 g/L.
b) How would you expect the changes to affect fermentation cycle times?
c) What process changes would you need to carry out with regard to fermentation management?
d) Draw up a checklist of what you would monitor once fermentation trials commence to ensure the process is under control and working satisfactorily.