biochemistry of beer
DESCRIPTION
By Dmitry Liskin Norfolk, VA October 2012. Biochemistry of Beer. According to Rheinheitsgebot (1516) beer should only contain: Water Barley Hops Yeast was discovered in 1800 by L. Pasteur. What is Beer?. Beer-like beverages appeared around 10,000 BC - PowerPoint PPT PresentationTRANSCRIPT
BIOCHEMISTRY OF BEER
By Dmitry Liskin
Norfolk, VAOctober 2012
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
High growth Aerobic process A few hours
Attenuation 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
Hardness affects mash pH and taste Malt
Color, flavor, aroma and body Hops
Preservation Bitterness, flavor, aroma
Yeast 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