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Brewing Beer
What is Beer?
• A mixture of malted barley, hops and water that is fermented with
brewer’s yeast
• Malted Barley = germinated barley that is then dried and ground into a
flour
• Malted barley develops enzymes that convert starches to sugars (glucose
and maltose)
• Sugars can then be fermented with yeast to make ethanol
• For maltose (malt):
C12H22O11+ H2O → 4CH3CH2OH + 4CO2
• For dextrose:
C6H12O6 → 2CH3CH2OH + 2CO2
Brewing
5 stages
• 1. Mashing
– The infusion of malt, water, and crushed cereal grains at a temperature
that encourages conversion of the starch  sugars
• 2. Boiling
– Concentrates the wort and potentially kills off harmful bacteria
• 3. Fermentation
– The addition of a yeast and hops to the wort – resulting in the formation
of ethanol and carbon dioxide (by-product)
• 4. Aging
– 2-24 weeks proteins (dead yeast cells) settle out of the beer and/or are
digested by enzymatic action
• 5. Filtration/Pasteurization
– Dead yeast cells etc are filtered out to help with the clarity of the beer,
filters can be cellulose or diatomaceous earth), beers may be pasteurized
if you drink beer in the US (haha)
Determining the Alcoholic Content
• Measure the density of the wort before you ferment (g/mL) this is called
the Original Gravity OG
• Measure the density of the fermented beer (g/mL) this is called the Final
Gravity FG
• % Alcohol = (OG – FG) * 132.7 (mL/g)
• Proof?
Boil water then turn off bunsen
add 15-30 g malt
Sterilize
fermentor/lock
Destructions
500 mL deionized water
in 600 mL beaker
Simmer 10-15 mins CAREFUL
Add 15 – 30 g Dextrose
And reheat carefully
Add 0.1 – 0.2 g hops
And simmer for 30 mins
(top up volume with H2O
when necessary) – then
add 0.1 g hops and boil 5
mins uncovered
Take 15 ml in a
beaker let it cool
and Pipette 5 mL
wort into a
weighed small
beaker get density
Cool wort in ice bath
At 30oC add pinch yeast
Wait 2 weeks
Warm up the fermentor
(prevent thermal shock)