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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!