Transcript Biochemistry of Beer

By Dmitry Liskin
Norfolk, VA
October 2012
BIOCHEMISTRY OF BEER
WHAT IS BEER?

According to Rheinheitsgebot (1516) beer
should only contain:
 Water
 Barley
 Hops
 Yeast
was discovered in 1800 by L. Pasteur
ORIGIN OF BEER
Beer-like beverages appeared around 10,000 BC
 First evidence points at Mesopotamia region
 Is said to be responsible for development of
agriculture

WATER

Hardness

Carbonate – temporary
 Gave
birth to beers with malty, smooth finish
 Munich, Dublin, London, St.Louis, Milwaukee

Sulfate – permanent
 Bitter,
pale beers
 Burton-on-Trent

Other ions
zinc, copper are necessary for fermentation
 Iron, manganese and chloride will cause flavor
problems

BARLEY

Malt: barley that has been sprouted and dried
 Color
 Golden
to black
 Aroma
 Bready,
malty, nutty, toasty, roasty
 Flavor
 Caramel,
toffee, molasses, coffee
 These characteristics develop due
to non-enzymatic browning reactions
CARAMELIZATION
Thermal decomposition of sugar, pyrolysis
 110 oC – 180 oC
 Low-moisture
 Produces a variety of products

MAILLARD REACTIONS
Reaction between amino acid and sugar
 48 oC – 230 oC

HOPS
Beer preservation
 Bitterness
 Flavor
 Aroma

YEAST
Brewers’ best kept secret
 Converts fermentable sugars to alcohol
 Top fermenting – ale; bottom - lager
 Contributes to flavor
with other byproducts

 Fusel
alcohols
 Esters
 Aldehydes
CLASSIC BEER STYLES
Bitters and Pale ale
 Stout
 Scottish ale
 India Pale ale
 Lager

BITTER AND PALE ALE
The beer of an Empire (1702 – 1714)
 Use of coal gave birth to pale malt

 Firm
hop bitterness
 Low hop character
 Touch of caramel from malt (bitters)
 Light fruity character from yeast
 About 5% alcohol
STOUT
Dark beer with roasty character
 Refreshing low alcohol to warming high gravity
beers

 Dry
stout
 Sweet stout
 Oatmeal stout
 Imperial stout
SCOTTISH ALE
Malt sweetness, smoky
 Clean finish
 Low bitterness
 Wide range of alcohol levels
 60/-, 70/- and 80/
INDIA PALE ALE (IPA)
Bitter, hoppy ale
 Crisp finish
 Malty, some caramel flavor
 Moderately strong
(5% - 7.5% alcohol)

LAGER
Malt focused beers
 Low hop character
 4.4% – 5.4% alcohol
 Clean finish
 Most food friendly style

MAKING OF BEER - MASHING
Base malt with specialty grains
 Mashing

 Hydration
of malt
 Gelatinization of starches
 Release of natural enzymes
 Conversion of starch to
fermentable sugars
ENZYMATIC ACTIVITY

Starch conversion
(60 oC – 75 oC)





Alpha-amylase
Beta-amylase
Limit-dextrinase
Alpha-glucosidase
Protein rest


Proteases
peptidases
BOILING THE WORT

Beer clarity
 The
hot break – protein coagulation
 The cold break – protein coagulation

Hop additions
 Bitterness
– 60-90 min
 Hop flavor – 20 min
 Hop aroma – 5 min or dryhopping
ALPHA ACID ISOMERIZATION

Alpha acids = Bitterness of beer
 Humulone
 Cohumulone
 Adhumulone

Measured by IBU’s (International Bittering Unit)
1
IBU = 1 mg alpha acid per 1 L
FLAVOR AND AROMA COMPOUNDS

Myrcene – pungent

Humulene – delicate and refined

Caryophyllene oxide – herbal/spicy
FERMENTATION
Beer is born when yeast is pitched
 Yeast characteristics

 Type
– Lager, Ale, Weizen
 Flavor – malty, fruity, woody, etc.
 Attenuation – degree of fermentation
 Temperature – impacts flavor
 Flocculation – precipitation of yeast

Sugar, oxygen, nitrogen and minerals are
needed
YEAST AT WORK

Adaptation




Attenuation





High growth
Aerobic process
A few hours
Production of alcohol
Anaerobic process
Fermentation of simple sugars
4 – 10 days
Conditioning


Conversion of byproducts to ethanol
Flocculation
YEAST BYPRODUCTS
Diacetyl and pentadione – buttery flavor
 Acetaldehyde – green apple aroma and flavor
 Fusel alcohols – oxidation to esters; fruity
aroma
 These byproducts will be metabolized during
conditioning stage

FINISHED PRODUCT

Water


Malt




Preservation
Bitterness, flavor, aroma
Yeast


Color, flavor, aroma and body
Hops


Hardness affects mash pH and taste
Alcohol, flavor, aroma, clarity
Combination of these factors gives the finished product
Complex flavors are desired while complicated ones to be
avoided
ACKNOWLEDGEMENTS

Referenced literature
Randy Mosher “Radical Brewing”
 John Palmer “How to Brew”
 Ray Daniels “Designing Great Beers”
 Jamil Zainasheff and John Palmer “Brewing Classic
Styles”
 BYO “Brew Your Own” magazine

O’Connor Brewery
 Christopher Newport University department of
Molecular Biology and Chemistry
 Fellow brewers
