Transcript Barley to Beer The Science Behind Brewing

Barley to Beer
The Science Behind Brewing
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Ingredients of Beer
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Barley (Hordeum vulgare )
Hops (Humulus lupulus )
Yeast (Saccharomyces cerevisiae)
Water
Barley
• Barley is selected to have a high starch to
protein ratio as protein causes cloudiness in
beer
• Barley has been bred to have a small amount of
husk as the husk contains tannins that taint the
flavour of the beer
• 90% of the barley grown throughout the world
(1980 figures) does not meet minimum
standards and is therefore used for feed
Barley
Hops
Hops
Hops
Yeast
Processes
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Malting (7-9 days)
Mashing (1-3 1hrs)
Boiling and adding hops (around 1hr)
Chilling
Fermenting (2-8 weeks)
Bottling / Kegging
Conditioning (1 week – 2 years)
Malting
• The purpose of malting is to activate enzymes in
the grain.
• The process of malting includes:
– Germinating by wetting the grain until the ascospore
reaches aound 70% of the length of the grain
– Drying in a kiln
• Around 80°C for light malts, 105°C for dark malts
• Varying the humidity and temperature of the kiln changes the
malt flavour
Mashing
• Malted barley is added to water in a process
called mashing
• The aim of mashing is to convert the starch in
the malted barley into sugars using the enzymes
activated by the malting process
• Sugars dissolve into the water to create a sweet
malty liquid know to brewers as the ‘Wort’
• Different enzymes work at different temperatures
and pH’s
• It is very important to have accurate control over
the temperature of the mash
Enzymes in malted barley
Enzyme
Optimum
Temperature
Range
Working pH Function
Range
Phytase
30-52°C
5.0-5.5
Lowers the mash pH. No
longer used.
Debranching
(var.)
35-45°C
5.0-5.8
Solubilization of starches.
Beta Glucanase
35-45°C
4.5-5.5
Best gum breaking rest.
Peptidase
45-55°C
4.6-5.3
Produces Free Amino
Nitrogen (FAN).
Protease
45-55°C
4.6-5.3
Breaks up large proteins
that form haze.
Beta Amylase
55-66°C
5.0-5.5
Produces maltose.
Alpha Amylase
68-72°C
5.3-5.7
Produces a variety of
sugars, including maltose.
Amylase at work
Starch + amylase + H2O
 starch-amylase complex
maltose + starch + amylase + heat
• Amylase works by clipping off one maltose
unit at a time from the large starch
molecule. Thus starch is both a substrate
and a product of the reaction.
Maltose
C12H22O11
A note on water
• The characteristics of water have defined
the types of beer brewed in different parts
of the world. A good example of this is
Guinness brewed in Ireland. The water
used to make Guinness is very hard and
alkaline. Using dark malts reduces the
alkalinity of the mash so that the enzymes
are working in their optimal range.
Boiling
• Boiling the wort has 3 purposes:
1. Steralize the beer
2. Denature proteins that otherwise make the
beer cloudy. The proteins form clumps and
drop out of the beer.
3. Add hops for bitterness, flavour and aroma
Adding hops
• There are many different varieties of hops
available that each have their own unique
flavour and bittering properties.
• There are two main categories of hops,
these are:
– Bittering (e.g. Pride of Ringwood)
– Aromatic (e.g. Cascade, Saaz)
Bittering hops
• Hops contain alpha acids (a resin) that is
made up of three closely related chemical
compounds (humulone, cohumulone, and
adhumulone)
• Bittering hops are added early to the boil
to extract as much of the alpha acids as
possible
International Bittering Units
(IBU’s)
• IBU’s are a standard used to assess the
bitterness of beer.
• IBU’s are calculated using the following formula:
• IBU's = ((Weight in ounces) x (%alpha acid) x (K)) / 7.25
Boil Time
45 min. to 60 min.
20 min. to 40 min.
O min. to 10 min
Constant (K)
K = 28 to 30
K = 8 to 12
K = 0 to 5
Aromatic Hops
• Contain essential oils that add a ‘hoppy’
flavour and aroma to the beer.
• The essential oils are volatile and
therefore aromatic hops are only added at
the end of the boil to avoid evaporation
Chilling
• After the boil the beer is chilled rapidly
• Chilling rapidly is desirable as it causes
remaining undesired proteins to precipitate
out of the beer preventing chill haze
Fermenting
• Yeast is added to the wort to convert the maltose
into alcohol and CO2
• Yeast contains an enzyme called zymase which
is the catalyst of this two step reaction
• The maltose is first converted to simple sugars,
such as glucose, and then into ethanol and CO2
C12H22O11  2C6H12O6
C6H12O6  2CH3CH2OH + 2CO2
Lager vs Ale
• Yeasts can be broken down into two main
categories these are
– Top fermenting (Ale yeasts) and
– Bottom fermenting (Lager yeasts)
Ale yeast
• Top fermenting
• Temperature of fermentation around 20°C
• Fermentation time approx 2-3 weeks
– Eg. Coopers Pale Ale, Guinness, Cascade
Pale Ale, Traditional English Bitters
Lager yeast
• Bottom fermenting
• Temperature of fermentation around 10°C
• Fermentation time approx 4-8 weeks
– Eg. VB, Tooheys New, Heineken,
Stella Artois, Pilsner Urquell
Bubbles
• There are two ways to get bubbles into
beer
– Using fermentation by adding a small amount
of sugar prior to bottling or kegging (e.g.
Coopers)
– Pressurizing using bottled CO2 and a
regulator (e.g. VB)
My Brewery
Mash Tun
Temperature controller
Heat the wort
Boiling Tun
Counterflow chiller
Culturing yeast
Fermenting