Unit 4: Fermentation Flashcards
Why yeast must be stored carefully?
The cured yeast must be stored chilled(1-2 degrees C). Needs to be handled gently so it doesn’t “stress” the yeast.
If yeast is stressed it will not ferment the sugars fully and might produce unpleasant flavours.
*everything used for yeast storage and handling must be clean and free of unwanted microbes
**Store no longer than 5 days
How to maintain healthy yeast?
Store chilled at 1-2 degrees C.
Store for no longer than 5 days
Simple technique for measuring yeast health?
Yeast viability. Measure healthy yeast cells under microscope
How is yeast added to cooled wort?
Laboratory culture > remove from storage > laboratory propagation > brewery propagation >
Pitching (yeast added to fermenter along with wort)
Cropping (once beer is fermented the yeast is removed)
What temperature should yeast be stored at and for how long?
1-2 degrees C.
Store for no longer than 5 days
Yeast storage vessel has a mechanical stirrer to stir the yeast every now and again
What happens if you add too little or too much yeast to the fermentation process?
Too little and the beer has too much sugar and not enough alcohol (the yeast get stressed and die).
Too much and fermentation happens too quickly and the beer has too much CO2 and becomes overly foamy (creates a big mess)
What are the steps to the yeasts cycle?
Pitch
Ferment
Crop
Store
Re pitch
Whats the name of the fancy microscope slide that the yeast slurry goes on? and why
Haemocytometer
(used to count blood cells)
used in this situation to count all the yeast cells that are dead (yeast concentration) (the blue dye that is added will only dye the unhealthy cells)
*called yeast viability
What is acid washing?
Some brewers wash their yeast with acid to kill off any unwanted bacteria
How is yeast pitched to the fermentation vessel?
-Yeast storage vessel
-Pitching pump (handles yeast slurry gently)
-Yeast counting meter (measures the amount of yeast slurry that gets added)
-Flow meter (yeast gets pitched into the cooled wort FIRST before they both travel to the fermentation vessel
How long does the fermentation process usually take?
6-7 days
Day 5 the alcohol level is no longer increasing
Day 6 the temperature is slowly brought down in preparation for maturation
Day 7 Done
What is the main type of fermentation vessel?
Cylindroconical Fermenters
Fitted with cooling jackets
Can be 10 m tall containing 100L (1 hectoliter)
Conical base helps to collect the yeast that settles out at the end
What is another main type of fermentation vessel?
Flat based or square fermenters
Good for ale fermentation where the yeast floats to the top
Coiled pipes are submerged and they get pumped with cool water to bring the temp down
**dying out because they are difficult to clean and expensive to maintain
What is the most Traditional vessel used for fermentation?
Wooden Fermenters (vats)
over 100 years old
hard to clean (less hygienic because its wood)
How is ale yeast “cropped” from a flat based fermentation vessel?
It gets skimmed (skimming board) into a collecting device (looks like the collecting duct in a nephron)
