The Chemistry of Beer

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The Chemistry of Beer

• Jim Enterkin
• LDM group Special Talk
• 5/22/09

2
Outline

• History
• Ingreedients
• Barley, Hops, Yeast, Water
• Brewing process
• The processing, and what effects we expect them
  to have on properties of the final product
• Beer characteristics
• The properties that we observe, and how they were
  derived from the processing of the ingredients
• Conclusion links for more info

3
History

• Beer is older than recorded history
• How and when it was discovered is unknown
• Evidence that barley was used for fermentation
  prior to the baking of bread
• Likely accidental discovery
• Grain at some stage of germination immersed in
  water
• Wild airborne yeasts land in water
• Natural fermentation
• Some brave soul drinks this water
• Not only was it tasty, but it got him/her
  buzzed!!!!

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History

• Beer is the reason for civilization as we know it
• Civilization depended upon nomads settling into
  villages
• Nutrition and longevity actually decreased as
  humans moved into farming villages
• Main reason to settle into villages was a steady
  supply of grain
• Why would the steady supply of grain be important
  enough to endure worse nutrition and shortened
  lifespan?

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History

• Beer improved health and hygiene
• Especially in populated areas, water was often
  highly contaminated
• Beer is completely safe
• No organisms that are harmful to humans can
  survive in beer
• Combination of alcohol, pH, and CO2 content

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History

• Ancient Babylon
• 4000 BC
• Sophisticated brewing techniques
• Beer integrated into religious ceremonies
• 2000 BC
• More than a dozen beer styles from various
  ingredients
• Ancient Egypt
• Beer brewed, sold, and served exclusively by
  female brewsters
• Brewsters held high social status

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History

• Middle Ages
• Beer as important as bread in diet
• Beer brewed in the home or in monasteries
• Monasteries advanced brewing techniques
• For the nutritional needs of monks and pilgrims
• Gained reputation for superior quality beer
• Sale of beer helped fund monasteries
• Some communal brewhouses arise by late middle ages

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History

• Colonial America
• Beer brewed mostly by women
• Beer brewed mostly in the home
• Brewing of beer in was a standard household
  activity, like baking bread

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History

• Uniformity of lager beers
• Industrial Revolution
• Trains and refrigeration lead to mass produced
  and shipped beer
• Prohibition and the depression lead to
  consolidation of the industry

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History

• Revival of Beer
• 1971, England, CAMRA (CAMpaign for Real Ale)
• Cold War
• Americans stationed in Europe experience
  different styles of beer
• 1979, USA, legalization of homebrewing
• Today Craft brews is the fastest growing
  segment of the beverage industry

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History

• Louis Pasteur (1822 1895)
• Work in microbiology stemmed largely from desire
  to understand role of yeast in fermentation
• Disproved spontaneous generation
• Developed germ theory
• Pasteurization
• Anaerobic respiration
• S. P. L. Sorenson (1868 - 1939)
• Developed pH scale for more accurate control of
  wort production (1909)

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Outline

• History
• Ingreedients
• Barley, Hops, Yeast, Water
• Brewing process
• The processing, and what effects we expect them
  to have on properties of the final product
• Beer characteristics
• The properties that we observe, and how they were
  derived from the processing of the ingredients
• Conclusion links for more info

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Types of Grain

• 2-row Barley
• Higher extract, less husk
• Preferred by craft brewers,
• home brewers, and European
• breweries
• 4-row Barley
• Used only as cattle feed
• 6-row Barley
• Preferred by large U.S. breweries
• Yields more amylases to help break down the cheap
  adjuncts (i.e. rice and corn)
• Other Grains
• Wheat, Oats, Corn, Rice

http//www.extension.umn.edu/distribution/cropsyst
ems/components/7658-9.html
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Malting

• Grain (usually barley) is malted
• Harvested grain is soaked in water until it
  germinates
• This activates amylases (and proteases)
• Grain is dried
• This halts the conversion
• Acrospires (sprouts) are removed
• Grain is cured
• usually at least one month

Barley Amylase
http//www.scientiaevitae.de/gb/2/5/beer.htm
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Barley Modification

• Acrospires eat endosperm as they grow during
  malting
• Acrospire is the sprout, endosperm is its food
  source (full of starch)
• Acrospires will continue to eat endosperm until
  it is depleted or they are stopped by the
  maltster by heating and drying
• Longer acrospire growth leads to
• More endosperm consumed and less fermentable
  sugar
• More amylases are activated
• More yeast nutrients released
• Clearer beer and more complete fermentation

http//www.scientiaevitae.de/gb/2/5/beer.htm
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Malting

• Toasting or Roasting
• Varying heats hotter for darker malts
• Varying times
• Varying fire sources

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Malt

• Germinated and crushed grain
• Amylases (and proteases) accessible but inactive
• Starches from endosperm partially broken down

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Hops

• Used in continental Europe since 700s AD
• Introduced to Britain in 1500s by Flemish
  immigrants
• Didnt replace use of other herbs for over 200
  years after
• Bog myrtle, horehound, alehoof, buckbean, wormwood

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Hops

• Humulus lupulus (family Cannabinaceae)
• Perennial vine
• Flowers of female plant grow into strobiles
  (cones) composed of leaflike bracts and
  bracteoles
• Bracteoles have lupulin glands
• Lupulin glands produce resins containing alpha
  acids
• These provide bitter flavor and act as a
  preservative
• Oils from the plant add flavor and aroma

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Alpha Acids

• Humulone R CH2CH(CH3)2
• Cohumulone R CH(CH3)2
• Adhumulone R CH(CH3)CH2CH3

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Hops

• Bitter herb grown on a vine
• Alpha acids bitter taste and preservative
• Aromatic oils

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Yeast

• The most mysterious ingredient for most of the
  history of beer, but also the most important
• Called God is good by medieval brewers as it
  turned wort into beer and produced more of itself
• It is unknown whether yeast or dogs were the
  first domestic animal

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Yeast

• Through anaerobic respiration, it converts the
  malt sugar into alcohol, CO2, and other
  by-products
• Often removed after fermentation, and can be
  re-uesd
• Yeast is essentially a fermentation catalyst
• The word enzyme (meaning biological catalyst)
  originates from the Greek for within the yeast

http//www.biotech.seagrant.org/glossary.html
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Yeast

• 2 main types (for brewing purposes)
• Saccharomyces cerevisiae (ale yeast)
• Prefers warmer temperatures (20-25C) and will
  flocculate on top of the beer
• Saccharomyces uvarum (lager yeast)
• Prefers cooler temperatures and will flocculate
  at the bottom of the beer (5C)

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Yeast

• Fermentation catalyst

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Water

• 3 main concerns
• Flavor of water
• Nutrients for yeast
• Cant use distilled water
• pH effects how well enzymes make maltose
• Keep mash pH 5-5.5
• Ion concentration important
• e.g. Ca2, Mg2, CO32-
• Darker malts lower pH more than lighter malts
• Areas with water with natural higher pH (e.g.
  Ireland) produced darker beers than areas with
  water with lower pH (e.g. Czech Republic)

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Water

• The medium for fermentation

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Outline

• History
• Ingreedients
• Barley, Hops, Yeast, Water
• Brewing process
• The processing, and what effects we expect them
  to have on properties of the final product
• Beer characteristics
• The properties that we observe, and how they were
  derived from the processing of the ingredients
• Conclusion links for more info

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Brewing Process

• Sugar is extracted from grains
• Hops are added and wort is boiled
• Wort is cooled
• Yeast is added
• Wort ferments to become beer

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Mashing Lautering

• Mashing
• Malt is soaked in hot water
• 155F (68C)
• Amylases re-activated
• starches broken down to sugars
• Primarily maltose 2 glucose joined by a(1?4)
  linkage
• Proteins also broken down
• Processing of proteins and starches highly
  dependent on temperature
• pH also important for amylase activity
• Lautering
• Grains are rinsed until water comes through clear
• Extract all ingredients into wort to be boiled

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Boil

• Denatures and inactivates amylases
• Breakdown of starches halted
• Most proteins coagulate and settle out and can be
  removed
• Hot break
• Extracts alpha acids and oils from hops
• Isomerizes alpha acids to isoalpha acids
• Kills any microbes in the wort
• Caramelization of sugars

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Alpha Acid Isomerization
http//www.scielo.br/scielo.php?pidS0100-40422000
000100019scriptsci_arttext
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Pitching Yeast

• Addition of yeast to allow fermentation
• Wort must be at proper temperature for yeast to
  survive and flourish
• Slightly off temperatures lead to off flavors
• Far off temperatures lead to stuck fermentation
• Oxygen must be kept out
• Yeast only converts sugars to alcohol and CO2
  under anaerobic respiration
• With oxygen present, aerobic respiration will
  dominate

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Fermentation

• Yeast absorbs oxygen and sugar, and reproduces
  asexually
• When oxygen is used up, reproduction stops and
  fermentation (anaerobic respiration) begins
• Each glucose produces two molecules of ethyl
  alcohol and CO2
• C6H12O6 ? 2 CH3CH2OH 2 CO2 118 kJ (2 ATP)
• Large amounts of CO2 are produced and must be
  removed without letting oxygen in
• Airlock or water bubbler

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Fermentation

• When all fermentable sugars have been consumed,
  fermentation stops and yeast begins to go dormant
• Yeast settle out and the beer clarifies
• This yields a young beer
• Bad taste and smell
• High concentrations of diacetyl and other organic
  byproducts

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Conditioning

• Small amounts of remaining yeast continue to
  consume byproducts of initial fermentation
• Conditioning or aging, development of flavor

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Packaging

• Flat beer is packaged (bottle or keg) and must be
  carbonated
• Add extra sugar for natural carbonation by
  fermentation
• Artificially carbonate from gas source

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Outline

• History
• Ingreedients
• Barley, Hops, Yeast, Water
• Brewing process
• The processing, and what effects we expect them
  to have on properties of the final product
• Beer characteristics
• The properties that we observe, and how they were
  derived from the processing of the ingredients
• Conclusion links for more info

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Beer Characteristics

• Alcohol Content
• Flavor
• Malt, Hops, Yeast, Water
• Aroma
• Clarity
• Head
• Preservation

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Alcohol Content

• Measured by density
• Original gravity density of wort prior to
  fermentation
• Final gravity density of beer after
  fermentation
• Dissolved sugars lead to high density
• As sugars convert to ethyl alcohol, the density
  decreases
• The decrease in the density is directly
  proportional to the amount of alcohol present

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Flavor

• Sweet flavors from malt
• Dependent on types of grain and on grain
  modification
• Bitter flavors from hops
• Isoalpha acids balance sweetness of grain
• 15 100 ppm depending on beer type
• Aroma from hop oils mainly from later additions
  of hops

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Aroma

• Hop oils
• Small organic molecules
• Often aromatics
• Polyphenols
• Mainly from late addition of hops
• Aroma hops boiled for a short time (5 minutes)
• Dry hops (added after wort has cooled or just
  before packaging)

Phenol
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Clarity

• Filtering, siphoning, settling, racking
• Yeast
• Flocculency of yeast
• Polyphenols from hops
• Larger polyphenols become insoluble and form a
  permanent haze
• Small polyphenols agglomerate when chilled to
  form a chill haze

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Head

• Protein from grains
• Wheat proteins stabilize head
• Isoalpha acids
• Tensioactive properties of isoalpha acids
  stabilize head

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Preservation

• Alcohol is a natural preservative
• Alpha acids
• Act as a preservative by inhibiting the growth of
  bacteria
• Beta acids (also from hops) also help
• Decomposition on exposure to light
• Isoalpha acids are
• light sensitive
• Skunky flavor
• Only a few ppb

http//www.scielo.br/scielo.php?pidS0100-40422000
000100019scriptsci_arttext
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Outline

• History
• Ingreedients
• Barley, Hops, Yeast, Water
• Brewing process
• The processing, and what effects we expect them
  to have on properties of the final product
• Beer characteristics
• The properties that we observe, and how they were
  derived from the processing of the ingredients
• Conclusion links for more info

47
More Info

• Stephen Snyder, The Brewmasters Bible, New York
  HarperPerennial, 1997
• http//www.scientiaevitae.de/gb/2/5/beer.htm
• Hop Chemistry http//www.scielo.br/scielo.php?pid
  S0100-40422000000100019scriptsci_arttext

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Drink!

• And be merry
• Happy Memorial Day!