The Art of Brewing and The Biology of Lager Yeast Tom Pugh Miller Brewing Company

The Art of Brewing and

The Biology of Lager Yeast

Tom PughMiller Brewing Company

Purpose

• Provide a better understanding of...

– The brewing process

– Types of brewing yeasts

– Attributes important to the brewer

Kindly provided by Tom Pugh and David Ryder of Miller Brewing Company

The Art of Brewing


Definition of Beer

• An alcoholic beverage produced by the fermentation of sugar-rich extracts derived from cereal grains or other starchy materials.


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


History of Brewing

• Sumarian beer recipe– 3000 BC

• Resembled liquid bread:– Barley and Emmer– Spices / fruits– No Hops

• Safe, nutritious, and exhilarating beverage.


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.



• 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 . . .


….small animal which sips sugar through its snout, and excretes alcohol from its gut and carbonic acid from its urinary organ.



• 1866 - Louis Pasteur– Yeast was responsible for alcoholic

fermentation.

• 1883 - Emil Christian Hansen – Developed pure culture technique– Isolated pure cultures of brewing yeasts


Brewing Yeasts


Types of Brewing Yeasts

• Two types of brewing yeasts, originally classified on flocculation behavior…

• Top-fermenting– Ale yeast– Weiss yeast

• Bottom-fermenting– Lager yeast


Weiss Ale

LabLager


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.


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.


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

aromatic.Kindly provided by Tom Pugh and David Ryder of Miller Brewing Company

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


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 + - +


Distinguishing Characteristics

• Difficult to distinguish between different lager yeasts using conventional techniques– Colony and cell morphologies similar– Fermentation characteristics

• PCR - limited success

• Electrophoretic karyotyping


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


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


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


The Brewing Process


Ingredients

• Malted barley

• Cereal Adjunct

• Hops

• Water


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


Steeping

• Soak, aerate, drain.• 2 days


Germination

• Ventilated to remove CO2

• Repeated turning• 4 to 5 days


Cereal Adjuncts

• Types of adjuncts commonly used:– Corn grits– Rice– Corn syrups (high maltose and dextrose)

• Purpose:– Additional source of fermentable sugars– Lighter body


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


Hops


The Brewing Process

Brewhouse

Fermentation

Lagering

Step Purpose

Starch Sugars

EthanolSugars

CarbonationFlavor maturation

Wort production

Flavor production


The Brewing ProcessMalt Mill

Mash Tun CerealCooker

Lauter Tun

BrewKettle

Hot WortReceiver

WortCooler

FermentationBrink

Aeration

Lagering

Hops


Mash Tun / Cereal Cooker

• Activate malt enzymes

• Convert starch to fermentable sugars


Lauter Tun• Strainer


Brew Kettle

• Sterilization

• Protein coagulation

• Hop extraction

• Volatile removal




Lauter Tun

BrewKettle

Hot WortReceiver

WortCooler

FermentationBrink

Aeration

Lagering

Hops


Wort CompositionCarbohydrates

Fermentable Non-fermentable

73% Fermentable


Wort CompositionFermentable Sugars

** need to adjust to normal wort

Glucose FructoseMaltose Maltotriose


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



Lauter Tun

BrewKettle

Hot WortReceiver

WortCooler

FermentationBrink

Aeration

Lagering

Hops


Fermentation• Yeast growth• Alcohol and CO2

• Flavor compounds• Large - 600,000 L


Lagering• Carbonation • Off-flavor

reduction




Lauter Tun

BrewKettle

Hot WortReceiver

WortCooler

FermentationBrink

Aeration

Lagering

Hops


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


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


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


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


Vicinal Diketones

Threonine

a-ketobutyrate

pyruvate a-acetolactate

a-acetohydroxybutyrate Isoleucine

Valine

Diacetyl

Pentanedione

Buttery, butterscotch flavor


Thanks to David Ryder of Miller Brewing Companyand Tom Pugh, formerly of Miller Brewing Company,

for providing this presentation to the Saccharomyces Genome Databasefor dissemination to the yeast community.

Documents

The Art of Brewing and The Biology of Lager Yeast Tom Pugh Miller Brewing Company