Fermentation Management Flo Vialan (Director of Brewing - Purity Brewing Co)
Topics Covered:
Fermentation Vessels
Stages of Fermentation
Fermentation Controls
Fermentation Flavours
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Trouble
Q&A
High Alcohol
Esters
Diacetyl
Sulphur
Shooting--
Fermentation Flavours:
- Higher Alcohols -(Also known as Fusel Oils)
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Can give headaches
Is the by product of:
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Low levels produced by yeast in normal conditions
High levels produced when amino nitrogen depleted
- Factors that increase yeast growth increase Fusel Oil production
Compounds Threshold (ppm) Flavour description
n-
Propanol
600 Alcohol sweet
Isobutan
ol
100 Solve
ntIsoamyl alcohol 50-
65
Alcoholic, banana
Amyl alcohol 50-
70
Alcoholic, solvent
2-Phenyl ethanol 40 Rose
s
- Esters -90 Identified. Give Fruity and Flowery Flavours
Most Important Are:
- Production related to concentration of precursors and yeast strain
- Amount of acid and alcohol present:
Increased by:
- High Wort
Gravity
- Higher
Temperatures
- Zinc
Decreased by:
- Top pressure on the
vessel
- Deep vessels
- Yeast
Compound Threshold level (ppm) Flavour description
Ethyl acetate 30 Fruity, solvent-like
Isoamyl acetate 1.2 Banana, pear
Phenyl ethyl acetate 3.8 Roses, honey
Ethyl hexanoate 0.2
3
Apple, fruity, sweetish
Ethyl octanoate 0.9 Apple anissed
- Diacetyl -Butterscotch flavours
Created during the synthesis of protein when the
wort is depleted of FAN
Yeast will reprocess to ‘flavourless’ acetoin
Also a sign of anaerobic infection
Low levels accepted in ales, a sin in lager beers
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- Sulphur -!
Sulphytic (struck matches), sulphidic (eggs)
Will depend on the yeast strain used
Will increase with high gravity, sulphate and temperature
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- Acetyldehyde -
In pathway from Glucose to Ethanol
Produced early in fermentation but mopped up by yeast in
maturation
Flavour of ripe apples
Typical flavour in young, green beer
Amount is dependent on strain
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