section 3.1 wort boiling

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B r i l l i a n t B e e r C o l l e g e General Certificate - Brewhouse

Section 3.1 Wort Boiling

by Tim O´Rourke

August 2010

Duration 15 mins

1

T h e B r i l l i a n

t B e e r C o l l e g e

What the Section will cover

The purposes of boiling:

• sterilization,

• stabilization of enzyme action,

• evaporation,

• coagulation and precipitation of protein (trubformation) and beer haze precursors,

• flavour development other than hop bitterness

• colour formation.

Factors affecting the effectiveness of wort boiling.

The purposes of liquid adjunct additions to the

wort kettle.



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STEEPING GERMINATION KILNING MALT

INTAKEMILL

GRIST

CASE

MASH

MIXERLAUTER TUNCOPPERWHIRLPOOL

WORT

COOLINGFERMENTATION

CASK

RACKINGMATURATION FILTRATION CAN BOTTLE KEG

WATER

WATER

WATER

HOPS

SPENT GRAINTRUB & HOPS

CATTLE FEED

CO-PRODUCT

YEAST

CO-PRODUCT

BARLEY

GRIST

MALT

MASHWORT

BOILED

WORT

BRIGHT

WORT

YEAST

Maltings

Farm

Brewery



PURPOSE OF WORT BOILING

Clarified wort from separation is collected directly in

kettle (copper):

Sensible heat – the wort is first heated from around

780C to boiling.

Evaporation – the wort continues to be boiled and

water vapour and volatile compounds are removed for

between 5 and 10% of the kettle contents.

Wort boiling is the most energy intensive stage

of the brewing process.

A successful boil must be vigorous. The

principal variables are:1. Time - duration of boil (usually 60 to 90 minutes)

2. Vigour of boil - effected by design & fouling

3. Temperature - effected by pressure in pressurekettles only.



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B r i l l i a n t B e e r C o l l e g e

Reasons for Wort Boiling

Key Operation - essential for quality

1. Sterilisation2. Stabilisation

Halting of enzyme activity

3. Colour/Flavour developmentIncrease in wort colour and flavour-active components

Formation of reducing substances

4. ConcentrationEvaporation of water and other volatiles

5. Extraction/transformation of hop components

6. Trub formation

Formation/precipitation of protein-polyphenol complexes7. pH Decrease

8. Flavour stability - DMS and SMM



1. Sterilises the Wort

Obesumbacteria

Lactobacillus

Pediococcus

Acetobacter

Heating – boiling

sterilises the wort and

kills nearly all the micro-

organisms present.

Exceptions are

microbes which can

form spores – none are

beer spoilage

organisms.



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2. Halts Enzyme Action

Enzymes arebiological catalystswhich work becauseof their shape.

Heating – boilingbreaks down theinternal bonds and

the enzyme loses itshape and is no longeractive.



3 Colour and Flavour development

Wort darkens -melanoidin formation, polyphenol oxidation.

Key reactions• amino compounds and the carbonyl group ( C=O) of

reducing sugars→

unstable carbonyl-amino compounds.• on heating, they condense with polyphenols to produce

darker melanoidins

• also flavour-active compounds formed.

Wort colour < 1/3rd from wort boiling, mostly maltkilning.

Colour decreases during fermentation• unboiled wort 8.8 EBC units

• boiled wort 13

• finished beer 12.3

Maillard Reactions during heating (kilning, mashing and wort boiling )

Amino compounds

+

Reducing Sugars

brown colour

bready & malty flavour carbonyles, eg methyl butanals

O-hetrocyclics eg furfurol, HMF

N-hetrocyclics eg pyrroles



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4. Concentrates wort

Water is driven of assteam, concentrating thewort.

• Evaporation rates of 4 -10% now common.

• High energy usage.Energy recoveryimportant

Years ago, 15 -20% notuncommon –

• important in achieving thehigh strength worts, forbarley wines, strong alesand lagers.

• But easier to: -• Partigyle - collect and boil

the first (strong) wortsseparately.

• Use Kettle adjuncts - sugarand syrups to raise the wortOG.

Evaporation removeswater as water vapour.

Evaporation willconcentratethe wort.• Increase in OG• Decrease in volume

T h e B r i l l i a n t

B e e r C o m p a n y

Hops contributes bitternessand aroma- oils in lupulinglands.

Prevents kettle over boiling.

Enhances beer foamAdds to microbial stabilityof beer.

Helps clarification -hopback

5 Addition of Hops



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6. Reduction in wort nitrogen

There are a number

of nitrogen (proteincompounds in beer.

Amino acids

Hydrophobic foamproteins

High MW hazeproteins.

It is principally highMW haze proteins(6%) coagulated byboiling.

Figure1.8.3.8.1Relationshipbetweenhighmolecularweight nitrogencompounds(coomassiebluetest)

against timefromthestart ofboil forthreedifferent evaporationrateswithresultscorrectedto12degPlato.Source: ORourkeT Brewer1984.

0 20 40 60 80 10300

400

500

600

700

800

Trial A

Trial B

Trial C

%EvaporationCorrelationCoefficient

9.2 -0.980

12.5 -0.943

4.5 -0.930

TIMEFROMSTARTOFBOILINMINUTES



6 Trub (hot break) formation

Break - flocculent particles formed

Need to precipitate and remove them

Promoted by:-

• longer boiling times - 2 hour boil - all precipitated

• higher temperature

• e.g at 1400C – complete in 3 to 5 mins

• vigorous movement

•

low pH - optimum 5.2• some only precipitates as cold break when wort is

cooled

• some high mol wt coagulable nitrogen-containingsubstances (20mg/l) remain dissolved in the wort -contribute to chill haze in beer

• Copper finings improve break - covered later



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7. Reduction in wort pH

Typical wort & beer pH:

Wort-pre boil – 5.5 – 6

Wort post boil – 5.0 –5.5

Post ferment 4- 4.5

phosphates : 3Ca2+ + 2 HPO42- = 2 H + + Ca3(PO4 )2

polypeptides : polypeptide --H + Ca 2+ = polypeptide---Ca +2H+ these reaction continue throughout wort boiling

Lower pH favours

•

good precipitation of protein-poyphenols• decrease in wort colour

• a better, clean tasting hop bitterness

• More resistance to micro-organisms

• Poorer hop utilisation



8. Reduction of volatile compounds

During boilingvolatile compoundsfrom the malt andthe mash areremoved with thevapour

The effectiveness

depends on:Time.

Temperature

Vigour

Surface area

Surface tension

EFFECTOFEVAPORATIONONSOMEIMPORTANTFLAVOUR NOTES

EVAPORATION(%)

SULPHIDIC

GRASSY/GRAI

FRUITY

Figure1.8.2.5.1

1.0

0

0.8

0.6

0.4

0.2

1 2 3 4 5



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DMS - volatile compound from malt

DMS precursor SSM isfound in malt andsubsequently wort.

It is heat labile. DMS isvery volatile and is lostduring boiling.

Garlic/onion/cookedcorn aroma.

Taste threshold

40 -45 ppb

DMS control:

Malting procedureLong boil

Short hot stand

Possible pathways for the formation of dimethylsulphide

(DMS)

H C3

H C3

S+

CH2

CH2 CH HN

3

+COO

_

S

H C3

O

H C3

S-Methylmethionine

SMM

Dimethylsulphoxide

DMSO

Glucose +

S- amino acids

Dimethylsulphide DMS H C S C H33

enzymatic reduction

yeast & bacteria

Maillard

reaction

thermal

destruction



KEY POINTS FOR WORT BOILING Stabilise wort – physical & biological

Depend on time, temperature & vigour

Energy intensive – energy recovery

Balance between under boiling:

1. Poor colloidal stability

2. “Green/lagery flavours

Over boiling

1. Energy costs

2. Thin palate

Clean worts for flavour stability and filtration

performance.



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REVIEW

1 Name 8 reasons for boiling wort?Answer – 8.

2 What are the main variables when duringwort boiling?Answer - 3

3 How can the % evaporation rate bemeasured during wort boiling?Answer - 3

4 What flavour faults are likely to arisefollowing a poor boil?Answer - 2

5 What two compounds react together toduring wort boiling which subsequently mayeffect beer stability?Answer - 2

section 3.1 wort boiling

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