Yeast- Gimme Some Sugar

Taxonomy: Common yeast encountered in brewing •  ThemainculturedbrewersyeastisgenusSaccharomyces

•  Saccharomycesmeans“sugarfungus”•  S.cerevisiaeisaleyeast•  S.pastorianusislageryeast•  Tarulasporadelbruckii(formerlyknownasS.delbruckii)isinthe(Weihenstphen)weizenyeastblendalongwithS.pastorianus

•  ThereisadebatewhetherS.pastorianusbelongstothecerevisiaespeciesornot,butcurrentlyisconsideredseparate•  LageryeastusedtobeclassifiedasS.uvarumorS.carlsbergensis

Taxonomy: Common yeast encountered in brewing •  Sourand“wild”beers(e.g.LambicsandBrettbeers)utilizegenusBrettanomyces•  Brettanomycesmeans“Britishfungus”andwasoriginallyisolatedfromEnglishStockAleattheCarlsbergbreweryin1904bytheirtechnicaldirectorNielsHjelteClaussen.Someculturesavailableinclude:•  B.bruxellensis•  B.lambicus•  B.claussenii

•  BrettanomycesareslowgrowersthatareabletofermentcomplexsugarsthatSaccharomycesisnotabletoutilize

Commercial yeast strain attributes and types

Attributesaffectingyeaststrainselection:•  Attenuation-howdrythebeeris(69–80%)

•  LowforBritishaleyeasts,highforBelgianaleyeasts•  Apparentattenuation=(OG-FG)/(OG–1)

•  Flocculation–howwellyeastdropoutofsuspension•  LowforWeizens,highforBritishAleyeasts

•  Alcoholtolerance(9–12%)•  Lowforlagers,highforBelgianaleyeasts

•  Fermentationtemperaturepreference(F)•  Low50’sforlagers,high60’sformostales,70’s–80’sforBelgianAles,low60’sforhybrids(Kolsch,Altbier,CaliforniaCommon)

•  By-productformation–goodandbadflavorsandaromas

Commercial yeast strain attributes and types

CulturedYeastStrainTypes(ThankstoFix,White,Zainasheff)•  Ale

•  Clean–lowesters:California/American,Scottish,European•  Fruity–highesters,diacetyl,rapidfermentation,highflocculation:British,Irish,Australian,someBelgian

•  Hybrid–Alestrainsfermentedatlowertemperaturesforlager-likecleannessandsomesulfur(Kolsch,Altbier)orlagerstrainsfermentedathighertemperaturesforsomeesters:(CaliforniaCommon)

•  Phenolic–Highattenuationandlowflocculationstrainsproducingphenolswithpepperyandcloveflavors:MostBelgianalesandGermanWeizens(whichalsoproducebananaflavors)

•  Eccentric–produceunusualflavorcompounds(earthy,barnyard,sour)aswellasphenolicsandmaybesuperattenuative:SomeBelgianstrains

•  Lager•  Dry–clean,crisp,refreshing:American,Scandinavian,someGerman•  Full–Clean,malty,rounded:MunichHellesandDunkel,etc.

Fermentation and the yeast life cycle

LagPhase(Latent)

Yeastuseenergyfromglycogenstorestomakeenzymesforgrowthandfermentation.Surveysugars,aminoacids,nutrients,andoxygeninenvironment.Transportcomponentsinandmakemissingones.

AcceleratingPhase(LowKraὒsen)

Yeastreproducethroughbudding,doubling1–3timesdependingoninitialcellcountandenvironment.Rateofcelldivisionincreases.Oxygenandsterolsareusedtomakecellwallmembranes.Ifwortcontainsmorethan0.4%glucoseitfermentsthatandbypassessterolpathway.

ExponentialPhase(HighKraὒsen)

Growthrateisconstantatmaximumforyeaststrainandconditions.Transportofaminoacidsandsugarsisveryrapid.Estersformedfromfattyacidsandalcohols.Fuselalcoholswillbeformedifcertainaminoacidsareinlowsupply.

DeceleratingPhase(LateKraὒsen)

Growthrateisdecreasing.Aleyeastwillhavemetabolizedmostsugars,butlagersstillreducingthem.Fermentationby-products(likediacetyl)arebeingmetabolized.Mayneedtoraisetemperatureupto68Fforadiacetylresttohelpwiththis,especiallyforlagersandhybrids.

StationaryPhase

Numberofyeastcellsremainsconstant.Thekraὒsenbeginstofall,thegravityapproachesFG,andtheyeastbeginstoflocculate.Rackingoffthetrubandyeastwillhelppreventoffflavorsduetoautolysis.

LageringPhase(MaybecombinedwithStationary)

Forlagersorhybrids,anadditionalcoldstorageof4–6weekswillhelpsmoothouttheflavors.Theyeastmustbeactiveduringthistime,sodon’treducetemperaturebymorethan5Fperday.

Zeroto15Hours Fourhoursto4days 3to10days 4to6weeks

Yeast Lifecycle

Fermentation and the yeast life cycle

LagPhase(Latent)

Yeastuseenergyfromglycogenstorestomakeenzymesforgrowthandfermentation.Surveysugars,aminoacids,nutrients,andoxygeninenvironment.Transportcomponentsinandmakemissingones.

AcceleratingPhase(LowKraὒsen)

Yeastreproducethroughbudding,doubling1–3timesdependingoninitialcellcountandenvironment.Rateofcelldivisionincreases.Oxygenandsterolsareusedtomakecellwallmembranes.Ifwortcontainsmorethan0.4%glucoseitfermentsthatandbypassessterolpathway.

ExponentialPhase(HighKraὒsen)

Growthrateisconstantatmaximumforyeaststrainandconditions.Transportofaminoacidsandsugarsisveryrapid.Estersformedfromfattyacidsandalcohols.Fuselalcoholswillbeformedifcertainaminoacidsareinlowsupply.

DeceleratingPhase(LateKraὒsen)

Growthrateisdecreasing.Aleyeastwillhavemetabolizedmostsugars,butlagersstillreducingthem.Fermentationby-products(likediacetyl)arebeingmetabolized.Mayneedtoraisetemperatureupto68Fforadiacetylresttohelpwiththis,especiallyforlagersandhybrids.

StationaryPhase

Numberofyeastcellsremainsconstant.Thekraὒsenbeginstofall,thegravityapproachesFG,andtheyeastbeginstoflocculate.Rackingoffthetrubandyeastwillhelppreventoffflavorsduetoautolysis.

LageringPhase(MaybecombinedwithStationary)

Forlagersorhybrids,anadditionalcoldstorageof4–6weekswillhelpsmoothouttheflavors.Theyeastmustbeactiveduringthistime,sodon’treducetemperaturebymorethan5Fperday.

Zeroto15Hours Fourhoursto4days 3to10days 4to6weeks

Yeast by-products and how to influence their production

UsuallyDesirableYeastDerivedAromasandFlavors•  FruityEstersfromAleStrains–apple,pear,cherry,plum,citrus,banana•  Faintpleasantsulfursmellfromlagerstrains• PleasantphenoliccompoundswithpepperyorclovearomafromBelgianandGermanwheat(weizen)strains• Pleasantearthy,barnyard,andsouraromasfromBelgianstrains

Yeast by-products and how to influence their production

UsuallyUndesirableYeastDerivedAromasandFlavors• Greenapplearomafromacetaldehyde(okayinBudweiser/AmericanStandardLagerstyle)• Buttery/butterscotcharomafromdiacetyl(okayinsomeEnglish,Irish,andScottishstyles)•  Softandspicyflavorsfromlowlevelsoffusel(C3+)alcohols(okayinbarleywineandsomestrongBelgianstyles)• Vinegararomafromaceticacid(okayinFlandersRedstyle)

Yeast by-products and how to influence their production

AlwaysUndesirableYeastDerivedAromasandFlavors•  Solvent(likefingernailpolishremover)aromafromethylacetate• Rubbery,rotteneggsaromasfromyeastautolysis(proteolysisofdeadyeastcells)• Harsh,hot,andsolventflavorsfromhighlevelsoffusel(C3+)alcohols• Medicinal/bandaidaromasfromwildyeastinfection

Creating healthy yeast For optimum fermentation

Creating healthy yeast For optimum fermentation

Youneedenoughyeastcellstoefficientlyprocessthesugars

Creating healthy yeast For optimum fermentation

YouneedenoughyeastcellstoefficientlyprocessthesugarsUnderpitchingleadstostressedyeastwhichleadstopoorfermentation

Pitching Rate Calculator http://www.mrmalty.com/calc/calc.html

Creating healthy yeast For optimum fermentation

Howdowegetmorecellseconomically?

Let’s Make a Starter

Step 1 MakesomefakewortusingDME

DryMaltExtract

Step 1 RuleofThumb:

About100gramsperLiterofwaterOr¾cup

Step 1 RuleofThumb:

1½cupfor2Literstarter

Step 1

Boil10minutes

Step 2 Coolwortandpourintoaflask

Thenpitchyeast

Step 2 Agitatebyhandtooxygenateorbetteryet,useastirplate

Step 2

Fermentfor24-48hours

Step 3 Chillyourmixture.

Yeastcakefirmsatbottom

Step 4 Decant

RemoveExcessDMEwort

Step 5 Pitch

(orbuildadditionalstarter)

Active Fermentation 12hoursfrompitching

Vigorous Fermentation 36hoursfrompitching

pitchyeast

Tips for optimum fermentation Inmostcasesit’shardtooverpitch

Tips for optimum fermentation Inmostcasesit’shardtooverpitchPitchandfermentonthecoolside

Tips for optimum fermentation Inmostcasesit’shardtooverpitchPitchandfermentonthecoolsideRaisetemptofinishfermentation

Yeast- Gimme Some Sugar

Thanks!