the art of brewing and the biology of lager yeast tom pugh miller brewing company
TRANSCRIPT
Purpose
• Provide a better understanding of...
– The brewing process
– Types of brewing yeasts
– Attributes important to the brewer
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Definition of Beer
• An alcoholic beverage produced by the fermentation of sugar-rich extracts derived from cereal grains or other starchy materials.
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History of Brewing
• Man has been making beer since the dawn of civilization.– Where grain was grown, beer was made.
• Sumaria (4000 BC) Sikaru• Egypt (3000 BC) Zythum• India (2000 BC) Sura• China (2000 BC) Kiu
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History of Brewing
• Sumarian beer recipe– 3000 BC
• Resembled liquid bread:– Barley and Emmer– Spices / fruits– No Hops
• Safe, nutritious, and exhilarating beverage.
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The Role of Yeast in Brewing
• Unwittingly, ancient brewers domesticated yeast.– Selected yeast that made good beer.
• Deduced that yeast was important to make beer.
– Collect the creamy foam or sediment from one brew. – Use it to pitch the next brew.
Did not know what yeast was.
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The Role of Yeast in Brewing
• 1680 Antonie van Leeuwenhoek – Observed yeast in beer.
• 1837 - Cagniard Latour– Microbe is responsible for alcoholic fermentation.
• 1839 -Justus von Liebig and Friedrich Wohler – Alcohol is produced by a chemical process in which dead and
decaying yeast participated.– Satired Latour’s theory in Annalen der Chemie . . .
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….small animal which sips sugar through its snout, and excretes alcohol from its gut and carbonic acid from its urinary organ.
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The Role of Yeast in Brewing
• 1866 - Louis Pasteur– Yeast was responsible for alcoholic
fermentation.
• 1883 - Emil Christian Hansen – Developed pure culture technique– Isolated pure cultures of brewing yeasts
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Types of Brewing Yeasts
• Two types of brewing yeasts, originally classified on flocculation behavior…
• Top-fermenting– Ale yeast– Weiss yeast
• Bottom-fermenting– Lager yeast
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Ale Yeast
• Predominant brewing yeast prior to the mid-1800s.– Displaced by lager yeast
• Strains are genetically more diverse - several origins
• Warm fermentation temperatures: 65 to 72 °F.
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Weiss Yeast
• Bavarian origins - closely related.
• Produces beer that has spicy, clove, vanilla, and nutmeg flavor notes - POF.– PAD1 gene phenylacrylic acid decarboxylase– Decarboxylation of ferulic acid forms 4-vinyl-guaiacol,
which gives the characteristic clove flavor.
• Warm fermentation temperatures: 65 to 72 °F.
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Lager Yeast
• Bavarian origin.– 1400s in Munich - cool fermentations (selective pressure)– Taken to Pilsen and Copenhagen in 1840s
• Pale malt, soft water, aromatic hops
• Became very popular - displaced ale yeast• Popularity fueled by advances of Industrial Revolution
– Steam power, refrigeration, railroads, pasteurization and filtration technology
• Strains are closely related - common origins• Cool fermentation temperatures: 42 to 52 °F• Beers are more delicate, clean, drinkable, and less
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Taxonomy
• Ale and Weiss yeasts - Saccharomyces cerevisiae– Polyploid and probably aneuploid.– Non-mating– Sporulates poorly and poor spore viability
• Lager yeast - Saccharomyces pastorianus– S. cerevisiae– S. carlsbergensis– S. uvarum– Sporulates very poorly - poor spore viability
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Distinguishing Characteristics
• Colony morphology• Microscopic appearance
– Chain formation
• Fermentation characteristics– Flocculation behavior / flavor compound profiles
• Growth at 37 °C• Melibiase• Electrophoretic karyotyping
Yeast 37 °C Melibiase POFLager - + -Ale + - -Weiss + - +
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Distinguishing Characteristics
• Difficult to distinguish between different lager yeasts using conventional techniques– Colony and cell morphologies similar– Fermentation characteristics
• PCR - limited success
• Electrophoretic karyotyping
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Genome Structure - Lager Yeast
• Allopolyploid and probably aneuploid.– Tetraploid
• Natural hybrid– S. cerevisiae and S. bayanus– S. cerevisiae and S. monacensis
• Contains two types of chromosomes– S. cerevisiae type– S. bayanus type
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Genome Structure
• Gene order and function highly conserved– Single chromosome transfer experiments
• Gene length similar, but nucleotide divergence.– Low levels of recombination between homeologues
Gene Nt. Identity AA. IdentityILV1 86 % 96 %ILV2 85 92MET2 84 94URA3 79 93
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Electrophoretic Karyotypes
Lager Ale WeissLabXII
IV
XV, VII
IVI
III
IX
V, VIII
XI
XVI, XIII
XII, XIV
T C C
Lager Ale Labcerev.bayan.
parad.pastor.
XIIIV
XV, VII
I
VI
III
IX
VIII
XI
XVI, XIII
XII, XIV
V
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Ingredients
• Malted barley
• Cereal Adjunct
• Hops
• Water
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Malted Barley
• Two types of barley– 2-rowed– 6-rowed
• Provides fermentable sugars, flavor, and color.
• Malting process:– Steeping– Germination– Kilning
• Purpose:– Activate enzyme systems– Preserve for brewhouse
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Steeping
• Soak, aerate, drain.• 2 days
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Germination
• Ventilated to remove CO2
• Repeated turning• 4 to 5 days
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Cereal Adjuncts
• Types of adjuncts commonly used:– Corn grits– Rice– Corn syrups (high maltose and dextrose)
• Purpose:– Additional source of fermentable sugars– Lighter body
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Hops• Spice of beer
– Provides aroma and bitterness
• Flower (cone) of a vine-growing plant– Humulus lupulus– Female triploid
• Used as:– Whole cones– Pellets– Extracts
Lupulin Glands
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The Brewing Process
Brewhouse
Fermentation
Lagering
Step Purpose
Starch Sugars
EthanolSugars
CarbonationFlavor maturation
Wort production
Flavor production
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The Brewing ProcessMalt Mill
Mash Tun CerealCooker
Lauter Tun
BrewKettle
Hot WortReceiver
WortCooler
FermentationBrink
Aeration
Lagering
Hops
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Mash Tun / Cereal Cooker
• Activate malt enzymes
• Convert starch to fermentable sugars
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Brew Kettle
• Sterilization
• Protein coagulation
• Hop extraction
• Volatile removal
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The Brewing ProcessMalt Mill
Mash Tun CerealCooker
Lauter Tun
BrewKettle
Hot WortReceiver
WortCooler
FermentationBrink
Aeration
Lagering
Hops
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Wort CompositionCarbohydrates
Fermentable Non-fermentable
73% Fermentable
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Wort CompositionFermentable Sugars
** need to adjust to normal wort
Glucose FructoseMaltose Maltotriose
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Wort CompositionAmino Acids (** adjust to normal wort)
Ala
Arg
Asp
Glu
Gly
His
Ile
Leu
Lys
Met
Ph
e
Pro
Th
r
Tyr
Val
Asn
Gln
Ser
Not included: Cys (2 ppm) and Trp (50 ppm)Kindly provided by Tom Pugh and David Ryder of Miller Brewing Company
The Brewing ProcessMalt Mill
Mash Tun CerealCooker
Lauter Tun
BrewKettle
Hot WortReceiver
WortCooler
FermentationBrink
Aeration
Lagering
Hops
Kindly provided by Tom Pugh and David Ryder of Miller Brewing Company
Fermentation• Yeast growth• Alcohol and CO2
• Flavor compounds• Large - 600,000 L
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Lagering• Carbonation • Off-flavor
reduction
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The Brewing ProcessMalt Mill
Mash Tun CerealCooker
Lauter Tun
BrewKettle
Hot WortReceiver
WortCooler
FermentationBrink
Aeration
Lagering
Hops
Kindly provided by Tom Pugh and David Ryder of Miller Brewing Company
Balanced Growth
• Yeast growth affects beer flavor.– Need balance between yeast growth and beer flavor.
• The brewer needs...– Desired flavor profile in desired time.– Sufficient yeast crop for subsequent fermentations.
• Oxygen is growth limiting nutrient.– Control point
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Yeast Metabolism During Fermentation
Sugars Oxygen
Amino Acids
Glucose
Pyruvate
TCACycle
EnergyCO2
Ethanol
Acetaldehyde
Organic Acids
Amino Acids
Unsaturated Fatty AcidsSterols
Esters
HigherAlcohols
VDK
SulfurVolatiles
Membranes
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Higher Alcohols
• Formed by the decarboxylation and reduction of a-keto acids.– From amino acid anabolism and catabolism.
Alcohol Amino Acid a-keto acidIsoamyl Leucine a-keto-isocaproate
Amyl Isoleucine a-keto-3-methylvalerate
Isobutanol Valine a-keto-isovalerate
Propanol Threonine a-keto-butyrate
Alcoholic, solventy, and fruity flavor notes
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Esters• Closely linked to lipid metabolism - growth.• Reaction of an alcohol and fatty acid intermediate
• Acetate esters– Ethyl acetate solventy, fruity, sweet– Isoamyl acetate banana– Phenethyl acetate roses, honey, apple
• Fatty acid esters– Ethyl caproate apple, aniseed– Ethyl caprylate apple– Isoamyl decanoate tropical fruits
Fruity flavor notes
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Vicinal Diketones
Threonine
a-ketobutyrate
pyruvate a-acetolactate
a-acetohydroxybutyrate Isoleucine
Valine
Diacetyl
Pentanedione
Buttery, butterscotch flavor
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