chapter 3 brewing process

8/13/2019 Chapter 3 Brewing Process

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v o l u m e i i i : t h e b r e w i n g p r o c e s s

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T HE P ROC E S S I N B R I E F

Brewing truly representsa marriage of art and science. It is interesting to notethat while brewers have developed a great deal of scien-ti c knowledge during the past 100 years to help themmonitor and measure components of brewing muchmore accurately, the essential procedures have changed very little over thousands of years.

The p ocess can be divided into foubasic steps:

1 Brewing2 Fermenting3 Lagering4 Finishing

Each of these steps will be discussed indetail th oughout this volume ofBeer: A Reference Guide to Ingredients, Brewing Scienceand Styles. But befo e that, conside howthe basic steps must be adjusted foeach b ew.

Mothe Natu e, afte all, is notknown fo he consistency. Fo eachc op and each individual ha vest,b ewmaste s must taste, test and as-

sess the ing edients to dete mine howthose mate ials will pe fo m du ingthe b ewing p ocess.

A b ewmaste s job is to cont ol andto in uence eve y step of the p ocess toachieve a bee s desi ed taste and qual-ity. Consistent esults depend uponca eful handling.

Th ee steps of the b ewing p ocess,


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b e e r : a r e f e r e n c e g u i d e

T HE P ROC E S S I N B R I E F

in pa ticula , focus heavily on natu esmethods of c eating and changing foodsubstances:

malting:

enzyme formation

G ains a e p edominantly composed ofsta ch, intended by natu e to se ve asa food sou ce fo the g owth of a newplant. When the g ain is planted intothe soil and wate ed, a plant begins tog ow. Natu e has p ovided each ke nelof g ain with an enzyme system thatallows it to conve t sta ches to suga s,needed fo the natu al g owth p ocessby the new plant.

This same natu al enzyme systemis used in b ewing to p ovide suga asfood fo the yeast that will conve t themalted g ain into alcohol and ca bondioxide.

In the malting p ocess whichtakes place befo e the g ain eachesthe b ewhouse the maltste ge mi-nates each ba ley ke nel in a cont olledg owing envi onment, without soil,enabling the g ains natu al enzymesystem to completely develop.( See also volume ii: ingredients. )

The ge minated g ain is then d ied,o kilned, to emove unwanted mois-tu e and stop the ke nels g owth without dest oying the f agile en-zyme system. The length of time theg ain emains in the kiln as well as thetempe atu e at which it is d ied dete -mines the esulting colo of the malt.It also in uences the avo of the maltby d iving off g assy and g een cha ac-te istics and developing toasted, nutty

and malty avo s.This malted g ain now possesses

a complete sta ch conve sion system.Most of the sta ch ese ves emain,but the cell walls a ound the sta chhave been b oken down by the enzymesystem. The ba ley ke nels emainingsta ch and enzymes will be used in theb ewhouse to p oduce wo t.

mashing:

wort production

In the b ewhouse, when g ound maltcombines with a la ge quantity of wa-te at the p ope tempe atu e, the en-zymes in the malt mash a e activated,and the apid conve sion of sta ches tosuga s, which began in the malt plant,continues.

The p oduction of wo t in theb ewhouse se ves as a key element in

the b ewing p ocess. The g ains usedand the time and tempe atu e schedulesfollowed dete mine the composition ofthe wo t suga s. This p ocess di ectlyimpacts the way the yeast pe fo msdu ing fe mentation, which also willaffect the avo of the nished bee .

fermentation:

alcohol production

Yeast is a living o ganism equi ing ba-sic nut ients to sustain life and g owth. An essential pa t of its diet is suga , which, unde ce tain conditions, yeast will conve t to alcohol, ca bon diox-ide and small quantities of many othesubstances to ultimately dete mine thenal bee avo cha acte istics.


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In the brewhouse, brewerscombine malt and other grains (depending on thebeer style) with water to prepare a liquid extract calledwort for the fermentation process. The compositionof the wort will have a signi cant in uence on the com-pounds produced during fermentation and on the ulti-mate aroma, taste and overall avor of the beer.

B R E W I N G

To achieve that end, fou main stepsoccu in the b ewhouse ope ation:

1 The milling process, oringredient preparation.

2 The mashing process, orextraction and conversion.

3 The straining operation, orclari cation and ltration.

4 The kettle operation, hop additionand subsequent cooling.

milling

The milling ope ation has somewhatcon icting objectives that must be del-icately balanced to g ind the sta chyinte io of the ke nels nely enough to

pe mit easy conve sion to suga s, whilenot g inding the malt husks becausethey a e needed late in the p ocess tonatu ally st ain and lte the wo t.

Some unmalted g ains such as ice,but unlike ba ley, can be g ound asnely as desi ed, since thei husks ohulls p eviously have been emoved.Co n g its need not be g ound and, as


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B R E W I N G

a esult, bypass the mills.The malt mill uses sets of olle s

and sc eens to sepa ate the husks f omthe ke nel and g ind the ke nels intothe g ist necessa y fo mashing.

mashing

Malt and wate a e ca efully measu edand mixed in the mash tank (o tun),essentially a cooking pot. This acti- vates the natu al enzymes that haveemained do mant since the kilningp ocess.

The e a e two majo g oups of en-zymes of conce n to a b ewe : thosethat act on sta ch to b eak it into sim-ple suga s; and those that act on p o-teins to b eak them into simple aminoacids. The suga s a e fe mented intoCO 2 and alcohol while the aminoacids a e essential fo the health and

nut ition of the fe menting yeast.Each enzyme ope ates at diffe ent op-timum tempe atu es, and the b ewemust cont ol the conditions ca efullyto ha ness the natu al activity du ingthe mashing p ocess.

Mash tanks f equently a e equipped with la ge, va iable-speed agitato s andsteam coils fo heating the mash at acont olled time and tempe atu e cycle.Fo an all-malt bee , typically (exceptdecoction mashing) only one mash ves-sel is equi ed a single-mash system.

Some all-malt bee s employ a dou-ble-mash system to boil small f ac-tions of the malt mash in steps in ap ocess called decoction.

Fo b ews that use both malt andan adjunct (with the exception of sy -ups o p e-gelatinized adjuncts), theb ewe uses two mash cooke vessels

1 Enzymes are active atdifferent temperatures

2 The stages of mashing favordifferent enzymes

3 Controlling the temperaturecontrols the wort composition

Control ofMashing:Temperature


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a double-mash system. In thesecases, the malt vessel is called themash tank and the one used fo theadjunct is called the cooke .

The mashing p ocess is about con-t olling conditions fo malts natu alenzyme systems to act on the ing e-dients to c eate food and nut ition fo yeast; to set the body, balance and nu-t itional p o le of the nished bee ;and to ext act o develop avo fo thebee s nal p o le. These conditionsinclude thickness of the mash, pHand, most impo tantly, tempe atu e.

Tempe atu e of mashing typicallygoes f om low to high, with stepwiseheating and ests at points whe e ce -tain enzymes a e active. The nal,hottest stage is often hot enough todeactivate enzymes completely, stop-ping thei activity and pe manently

setting the p o le of the wo t.

The e a e th ee main tempe atu eests in mashing (illustration at left):

1 Protein rest2 Conversion rest3 Mashing off (deactivation)

Protein rest

Du ing this pe iod, la ge p oteinmolecules in the malt b eak down intosmalle , amino acid f actions used bythe yeast late in the b ewing p ocess.In addition to p oviding nou ishmentfo the yeast, this p otein is impo tantto bee avo and foam. B ewe s oftencall this phase of the p ocess the p o-tein est.

Conversion rest

The mash tempe atu e is aised to the

ideal tempe atu e fo natu al enzymesto act on the sta ch f om malt and oth-e g ains, and conve ts it into fe ment-able suga s. The b ewmaste decidesthe deg ee to which this conve sion will take place lowe tempe atu esfo longe times fo mo e conve sion;highe tempe atu es fo sho te timesfo less.

Cont olling the conve sion tempe -atu e of the mash is c itical, becausethe p ocess is ext emely tempe atu esensitive. Small tempe atu e va iationscan esult in signi cant changes in wo t composition and, ultimately, theavo of bee .

Mo e conve sion means highe levelsof fe mentable suga s and lowe levelsof unfe mentable dext ins (sho t

suga chains that a e too la ge fo yeastto metabolize), which add body to bee . A g eate deg ee of conve sion means:

1 Lighter, less sweet and full body 2 Higher potential alcohol in the wort3 Lower calories and carbohydrates for

a given alcohol level

The efo e, the deg ee conve sion isc itical to the p o le of the bee be-cause it sets the alcohol content, thecalo ic value and, in pa t, the elativefullness, sweetness o d yness of thebee .

wort production: lauter ing

The next step in the b ewing p ocessinvolves sepa ating the dissolved ex-t act f om the malt husks and othe


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oils dissipate fai ly quickly, and ovetime hop acids isome ize and add bit-te ness to the bee . The amount and va iety a e dete mined by a b ewmas-te to c eate the desi ed hop cha acteand bitte ness level of a bee .

The boiling p ocess is a technicallycomplex p ocedu e. The length of theboil also can help dete mine colo andavo cha acte istics. The boil devel-ops impo tant avo s and emovesothe s by d iving g ainy and g assycha acte up the kettle stack.

W h i r l P o o l

Wo t ente s the whi lpool in a tangen-tial ent y that c eates the whi lpoolmotion. The whi lpool motion d awsthe t ub o kettle b eak out of the wo t via cent ifugal motion and fo ms

a t ub cone a pile in the bottomcente of the tank.

The clea wo t is decanted off, leav-ing behind the dense t ub pile.

wort production: cooling

Befo e moving on to fe mentation, theb ew must be cooled and p epa ed fo theaddition of yeast. Cooling p omotes thefo mation of a seconda y coagulation ofp otein called cold b eak o cold t ub.It is much smalle than the hot t ub pa -ticles fo med in the boiling step.

Cold t ub sometimes is emoved with an additional settling step. Asmall amount of t ub ca yove intop ima y fe mentation, howeve , oftenis desi able. T ub has some nut ient value and is necessa y fo the yeastsp ope g owth.


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Fermentation serves asthe foundation of the brewing process the conversionof wort into beer. Here, the yeast converts fermentablesugars created during mashing to alcohol, natural car-bonation (CO2 ) and compounds that determine theultimate avor pro le of the beer.Eve ything that occu ed in the malt-house and the b ewhouse involvedca eful p epa ation of the yeastnut ients and othe substances thatcould in uence the taste of the bee .Eve ything that occu s afte fe menta-tion p ima ily p ese ves the bee avoestablished by fe mentation.

In p actice, fe mentation fo lagebee s occu s in two distinct steps:

1 The primary fermentation.2 The secondary fermentation, or

the lagering or aging process.

The p ima y fe mentation takesanywhe e f om a few days to abouttwo weeks, depending on the yeast

st ain and bee style. Du ing this time,the yeast activity is g eatest and mostof the wo t suga s conve t to alcoholand CO2.

The seconda y fe mentation, o thelage ing o aging p ocess, takes seve al weeks at a minimum, and completesthe eduction of fe mentable ext actand helps achieve a c isp bee p o le

F E R M E N T I N G


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typical of lage styles. Ale fe menta-tions a e essentially complete afte thisp ima y fe mentation, and often onlyhave a sho t matu ation est o p oceeddi ectly to nishing with no aging.

primary fermentation

Yeast is blended into the wo t st eamin a p ocess called pitching. Cooled wo t must be injected with ste ile aio oxygen afte cooling to p ovide ap ope envi onment fo vigo ous yeastg owth.

Just as a bee has a ecipe fo ing e-dients amounts of malt, va ieties,ates and the timing of the hop addi-tion a bee also has a c itical ecipefo fe mentation.

The most c itical facto is the yeastst ain itself. The fe mentation isthe esult of the g owth and natu al

activity of millions of copies of itself.Yeast st ains behave diffe ently andadd diffe ent avo s to bee dependingon tempe atu es, concent ations, levelsof oxygen and in diffe ent wo ts. Theb ewmaste s job is to p ovide theconditions fo a pa ticula st ain top oduce the ight avo s fo the bee .

Many facto s can affect the ate offe mentation and, the efo e, the f uity, yeasty o acidic cha acte of the bee . Abee ecipe includes oxygen additionates, pitching ate, cooling, tempe a-tu e attempe ation tempe atu e, andate and timing of additional coolingafte p ima y fe mentation is nished.

At the completion of p ima y fe -mentation, the alpha bee is emovedf om the fe mento . Most of the fe -mentable suga s have been conve tedto alcohol and CO2, but the bee taste

2 BASIC CATEGOrIES OF YEAST

Lager Yeast Saccharomyces Uvarum or

Saccharomyces Carlsbergensis

G a y p f w mp a-u a d b m f a k du g f m a a d

ma u a . P duc c p, g yf u y a d ba a c d a a a

a ma k f ag y .

Ale Yeast Saccharomyces Cerevisiae

G a y p f wa m mp -a u a d p f

du g p ma y f m a-. A k w a p-f m g

y a . P duc f u y c a ac- a f a g a u f fu ,

u d a y .

F E R M E N T I N G


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The Hiory: In the mid-1880s, European brewers introduced the lagering oraging process in the United States. The technique ofusing ice for cooling and the subsequent developmentof refrigeration made possible year-round brewing oflager beers.

LAGERINGAGING

Lage ing is still pa t of fe mentationand uses suf cient amounts of yeast.This seconda y fe mentation takesplace eithe in lage tanks o in thesame tank as p ima y fe mentation af-te cooling and yeast emoval.

lager tanks and carbonation

Lage tanks usually a e built to with-stand highe p essu es. Fe mentablesuga s a e ve y low at this stage of thep ocess, and yeast activity and heatgene ation a e conside ably less.

Du ing the aging p ocess, bee e-mains unde elevated p essu es fo twoeasons to natu ally ca bonate thebee and to keep the bee unde CO2 p essu e, f ee f om the damaging ef-

fects of oxygen.The most impo tant pa t of the la-ge ing p ocess is the change in compo-sition of the bee itself the second-a y fe mentation. When the yeast hadplentiful food, it took what it neededand c eated a wide ange of fe menta-tion p oducts as it hu ied th oughthe p ima y fe mentation. The sec-

onda y fe mentation educes ce taincompounds p oduced du ing p ima yfe mentation that give bee a full, un-balanced o un nished taste. The e-sultant bee is clean, c isp and fullymatu e.

a bit about beechwood aging

Anheuse -Busch touts its beechwoodaging p ocess. Its p ima y pu pose isimp oving the yeast-to-bee contactto complete the matu ation p ocess oflage ing.

Th ough this p ocess, the yeast set-tles onto an eno mous su face a ea c e-ated by the beechwood chips, the ebykeeping the yeast off the bottom of thelage tank and g eatly inc easing its

contact with the bee . The inc easedsu face a ea allows fo complete matu-ation and slow, mellow blending. Thebeechwood chips add no avo to thebee . In fact, beechwood is used be-cause potential avo in uences a eeasily emoved f om its chips by a sim-ple cooking p ocedu e.


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To keep the lagered beeravor and clarity intact after packaging, brewers must re-move yeast and some unstable protein materials througha process called nishing. It requires two steps:Chillproof-ing andFiltration.

chillproofing

Among key bee quality cha acte isticssuch as taste, colo and cla ity, cla ityep esents the most immediately ob-se vable cha acte istic of a bee . Fol-lowing the lage ing p ocess, bee looksquite hazy because of p otein pa ticlesand esidual yeast suspended in thebee . Although p otein pa ticles maydissolve in the bee at oom tempe a-tu e, they become insoluble at the coldtempe atu es at which bee is se ved,c eating a visible haze. This type ofhaze is known as chill haze.

Since the combination of p oteinsand othe bee constituents calledpolyphenols cause chill haze, emovalof eithe component will p event it.Unfo tunately, it is not desi able to

fully emove eithe component. P o-teins p ovide foam stability and avocha acte istics. Polyphenols enhancethe snap and bitte ness of the bee andhelp p event undesi able aging effects.

The efo e, to p event the eactionthat esults in chill haze, some b ew-e s emove ce tain but not all ofthe p oteins f om the bee befo e the

lt ation step. This p ocess is known aschillp oo ng.

filtration

Th ough bee lt ation, b ewe s st iveto emove suspended pa ticles of yeast,p otein and silica gel, esulting in aclea , nished bee . Bee gets pumpedth ough special lte s coated with dia-tomaceous ea th ( de ) known as Kie-selguh lte s in Ge many. de is thefossilized emains of single-cell o gan-isms called diatoms.

When fo med into a lte cake onthe stainless steel sc eens inside theKieselguh lte , the small de pa ticlesc eate a depth lte . Mo e de is con-tinuously added th oughout the lteun to offset the inc easing amount of

insoluble mate ial coming in with thebee . The additional de is ve y im-po tant to the lte pe fo mance andcauses the cake to g ow as mo e beeis lte ed.

The esult is b ight bee with b il-liant cla ity at any tempe atu e. It is wo th noting some bee styles such asBava ian- o Ame ican-style Hefewei-

FINISHING


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FINISHING

zens a e left un lte ed and not chill-p oofed fo the white, cloudy, yeastyhaze typical of the style.

pasteurization

Pasteu ization is the p ocess of gen-tle heating and apid cooling of f eshpackaged bee to p event bacte ial con-tamination.

The lled and closed packages ofbee a e conveyed th ough diffe entsections of a tunnel pasteu ize andsp ayed with attempe ated wate in-c easing, holding, then dec easing thetempe atu e. This st accomplishes

pasteu ization, then apidly ecoolsthe bee within minutes.

Eve y package must be sp ayed with wate fo the necessa y time and of theco ect tempe atu es to eceive the to-tal pasteu ization heat units equi ed.Too little may esult in poo avostability of the bee because of theemaining live mic oo ganisms. Toomuch may have a cooking effect, caus-ing accele ated staling of the bee . Thebalanced, tightly cont olled and gentlet eatment esults in stable and f esh-tasting bee .


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FINISHING

chapter 3 brewing process

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