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TRANSCRIPT
Objective and Outline
• Objective– Identify practical solutions for keeping beer as fresh as
possible.
• Outline– Background
– What is freshness?
– Reactions in brewhouse, fermentation, & finishing
– Practical steps to freshness improvement
– Making decisions on freshness
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Background - Factors that Affect Beer Shelf Life • Microbiological spoilage
– Bacteria: lactic acid, diacetyl, H2S, etc
– Yeast: over- attenuation, over carbonation
• Physical stability
– Chill-haze
– Permanent haze
• Flavor stability
– Changes in flavor
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This talk will focus on flavor stability
Background - Why Worry About Flavor Stability?
• Customers want a consistent flavor
• They accept consistent flavor, even if it includes off-flavors– e.g. DMS, oxidation, light-struck
• They reject variable flavors – Beer will not meet their expectations
– Do not like surprises
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Freshness in the Marketplace • Wide freshness variation – confuses the customer
• Narrow range – customer gets a consistent product
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Fre
quen
cy
Stale Fresh
Fre
quen
cy
Stale Fresh
Freshness
• Freshness is how close a product is to when it was :
– Picked from the field
– Made in the bakery or brewery
• Implied:
– Better taste
– Better nutrition
– No artificial preservatives
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Changes in Beer • Freshness begins to decline once beer is
packaged
• The decline is accelerated by increased temperature
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0 100 200 300Days
80oF
70oF
36oF
Less
Fre
sh
Why Does Beer Lose Freshness?
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Staling is the sum of many flavor changes:
- no single compound or mechanism is responsible
- there is no single solution
Inte
nsi
ty
Time
Where Should You focus?
• Across the entire system
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Brewery Wholesaler Retailer
Brewhouse Fermentation Finishing Packaging
We will first look at the brewing process
First, a Word about Carbonyls
• A class of compounds that contain a C=O group
C=O
• Include:– long-chain unsaturated aldehydes.
• 1969 - trans-2-nonenal was shown to impart a stale, cardboard, flavor when added to beer.
– other volatile carbonyls: • ketones, esters
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A
B
Brewhouse Chemistry - Mashing and Lautering -
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Unsat. Fatty Acids
Carbonyls
Lipase
Polyphenols
Tannins
O2
Lipoxygenase
Malt polyphenolsMalt LipidsMalt Protein
Amino Acids
Protease
Oxygen is important in carbonyl production
Brewhouse Chemistry- Boiling -
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Polyphenols
Carbonyls
O2
Iso-alpha acids
Extraction
Isomerization
Tannins +
Protein Carbonyl-protein
Wort
protein
From
Mashing
Maillard
Products
Unsat. Fatty Acids
Heat
Amino acids Hops Sugar
Copper
Vessels
& coils
Oxygen and heat drive complex reactions
Malt
Tannins
Fermentation Chemistry
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Carbonyls
Alcohols Protein–
carbonyl
SO2
SO2–
carbonyl
Sulfate
H+
Yeast
Ethanol
Sugars
SO2
SO2 is an important anti-oxidant, especially in lagers
Carbonyls become bound to protein and SO2
Iron
Yeast
Iron
Uptake
Autolysis
Finishing and Packaging Chemistry
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Iron
Reactive Oxygen Species
O2- superoxide anion
HOO- perhydroxyl radical
H2O2 hydrogen peroxide
HO. hydroxyl radical
OxygenFilter medium
Chemistry in the Package- reactions involving oxygen-
Oxygen
Reactive Oxygen Species
Finished
Beer
Package
Iron &
Copper
Sulfur Dioxide
Iso-alpha acids
Sulfate
Sweet, fruity• e.g. Ethyl isovalerate
Side chain
PolyphenolsHarsh, astringent• tannins
+
Others reactions – oxidation of ethanol and higher alcohols
Ethanol
Diagram courtesy of Grace Darex Packaging Technologies
ingressD.O.
Chemistry in the Package-reactions independent of oxygen-
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SO2– carbonyl
Protein – carbonyl
Carbonyl +
Maillard Products +
Paper, cardboard
• e.g. Trans-2-nonenal
Solvent
• e.g. furfuryl ethyl ether
SO2
Other reactions
– esterification, etherification, glycoside hydrolysis, & ester hydrolysis
Ethanol
These compounds, which originated in the brewhouse,
result in stale flavors in the package
The Brewing Process -factors that are important for freshness-
• Yeast
– SO2
– O2 uptake
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Brewhouse Fermentation Finishing Packaging
• Oxygen
• Metal ions
• Oxygen
• Heat
• Oxygen
How can Freshness be improved?
• Maximal freshness can only be achieved by making improvements across the entire production chain
– Chain is as good as its weakest link
– Recommend that you do not only focus on one area
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Brewery Wholesaler Retailer
Brewhouse Freshness Best PracticesMashing
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Bottom
entry
Fore
masher
Course
grind Malt
No scorching or build-up No votex upon emptying
Water Effective mixing that minimizes foam and
creates no vortex
Pump seals maintained to
avoid air pick-up
Minimize exposure to air
Brewhouse Freshness Best Practices- Lautering -
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Bottom
mash entry
Side mash
entry
Minimal
Foam
Not exposing the
grain bed
or
Minimize exposure to air
Brewhouse Freshness Best Practices– Boiling -
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Gentle fill
minimizing foam
Avoid extended boil time
Efficient heat transfer – minimal scorching
No vortex during emptying Pump seals
maintained to avoid air pick-up
Avoid boil temperatures above 212 F
Minimize air and heat
Vigorous boil
Brewhouse Freshness Best Practices- Whirlpool-
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Tangential flow
Minimal foam on wort surface
Pump seals maintained to
avoid air pick-up
Gentle wortflow
Avoid excess time
Minimize air and heat exposure
Fermentation Best Practices
• Increase SO2 levels in lagers
– SO2 is an antioxidant
– below level requiring labeling
• Minimize yeast autolysis
– Can release iron into beer.
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Fermentor
Yeast
Maturation
Increase SO2 Reduce autolysis
Lower ferm. temp X
Lower aeration rate X
Lower pitch rate X
Increase yeast food X X
Lower maturation temp. X
Reduce maturation time X
Finishing Best Practices
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De-oxygenate adjustment water
Filter Beer
Tank
Water Filter
Gas with CO2
before filling
Use low iron D.E.
Chiller
Buffer
Chill-
proofer
Maintain to avoid oxygen
pick up
Seals maintained to avoid air pick-up
De-oxygenate water
Minimize air and iron pickup
Packaging Freshness Best Practices
• Minimize oxygen – Finished beer D.O. should be low (50 ppb)
– Bottles • Evacation
• CO2 flushing
• Proper adjustment of jetters
– Cans • Use CO2 flushing
• Bubble breakers
• Under-cover gassing with CO2
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Measuring Package Oxygen
• Shake-out method – fair– Better than not measuring oxygen – Detects high levels – Too inaccurate to be used for driving
down oxygen levels
• Dissolved oxygen – better – Pierce package and run beer
through a D.O. meter. – Detects beer D.O. levels - but not
headspace oxygen
• Total package oxygen - best – Oxygen in beer + headspace oxygen – Semi-automatic
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Packaging Materials Best Practices
• Many more times the oxygen may enter the package over its shelf-life as is present immediately after packaging
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Package Type Source of oxygen ingress Improve freshness through:
Glass Bottle • Crown • Barrier crown - better• Absorbing crown – best
Plastic Bottle • Closure
• Bottle
• Barrier crown – better • Absorbing crown – best
• Oxygen barrier – nylon • Absorbing technology – e.g. Co
Can • Minimal ingress
Diagram courtesy of Grace Darex Packaging Technologies
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0 100 200 300
Days
Distribution Chain Control- It all about Time and Temperature -
• Higher temperature leads to a rapid loss of freshness – 2 to 4 times more for every 18oF
(10oC)
– Beer stored at 80o F for 50 days will be as fresh as beer stored at 70oF for 100 days
• Draft beer that is kept cold will remain fresher than packaged
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40oF
80oF 70oF
Keeping beer cool and for shorter times
means beer is consumed fresher
– local production and distribution helps
Less
Fre
sh
Tools to Assess the Process
• Process assessment
– Visual:
• Vortexing
• Excessive foam in brewery vessels
• Scorching on heat exchange surfaces
– Measurement
• Excess levels of dissolved oxygen where you have clear liquid
– Lauter
– Wort receiver
– Kettle knock out
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Freshness Measurement • Focus on a reliable measure related to the consumer
experience. – Sensory is the best measure
– Avoid complex chemical analyses
– Measurement of radicals is mainly related to SO2 and or iron level
• Develop a Freshness Panel– Train using in-house or outside expertise (FlavorActiv)
– Develop a scale: e.g. 1 to 10
• Use the panel to provide feedback on experiments and process improvement efforts– Does a process change improve freshness?
– Is the cost worth it?
– What is the shelf-life of a beer? 38
Beer Shelf-Life Determination
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4.5
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5.5
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6.5
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7.5
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8.5
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0 50 100 150 200 250 300
Days
70 F
32 F
Less
Fre
sh
Shelf-life is the time before the beer tastes unacceptably
different from fresh beer
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Summary
• Freshness of beer in the marketplace is affected by:– Production methods from the brewhouse to the finished package
– Storage conditions after the beer is packaged
• The freshness of beer that reaches the consumer can be enhanced by systematically improving each link in the chain as much as practically possible
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Brewery Wholesaler Retailer