biochemistry of beer

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