Presentatie

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Verlenging van de smaakstabiliteit van bier
Prof. dr. G. Aerts KaHo Sint-Lieven Technical
University guido.aerts_at_kahosl.be
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coincides with the early appearance of stale and
oxidised flavours
coincides with
? a decrease in bitterness intensity and
Beer ageing
bitterness quality
oxidative degradation of especially
trans-iso-a-acids
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Beer ageing
coincides with
? a decrease in bitterness intensity and
bitterness quality
? a loss of hoppy flavours ? a decrease in ester
aroma ? an increase in and a release of free
fatty acids oxidation aldehydes ? an increase
of Strecker degradation aldehydes ? an increase
of HMF and furfural ? an increase of dicarbonyls,
and other ageing markers ? a decrease of SO2
4
Beer ageing
is accelerated by
masking odours and aromas can retard the sensory
impression of ageing beer
? storage and distribution at temperatures gt 7
C ? light ? O2 ingression ? pH lt 4.5 ?
pasteurisation ? residual pro-oxidants and metal
ions ? absence of SO2
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Beer filtration and packaging
great investments are done by the brewing industry
the beer matrix seems extremely sensitive
for oxygen
THE ROLE OF THE FINAL STEPS IN BEER PRODUCTION
AVOID OXYGEN UPTAKE
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THE ROLE OF THE FINAL STEPS IN BEER PRODUCTION
Beer filtration and packaging

• - use of deoxygenated water
• purging of vessels and pipelines with CO2 prior
  to beer
• transfer
• ensure high flow rates of CO2 and enough
  pressure during
• bright beer handling
• - double pre-evacuation better than single
• - fobbing of bottles more effective for removing
  
• headspace oxygen than CO2 blowing

more and more CO2 is regarded as the 5th
ingredient
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THE ROLE OF THE FINAL STEPS IN BEER PRODUCTION
Beer filtration and packaging
The oxidative stress of beer is in conflict with
- pasteurisation thermal load - presence of
pro-oxidants (e.g. residual a-acids) - presence
of Cu/Fe ions - oxygen migration through the
cap, through bottle (PET)
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THE ROLE OF THE FINAL STEPS IN BEER PRODUCTION
Beer filtration and packaging
Therefore
best flavour stability is obtained by
combination of HMW gallotannin PVPP
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THE ROLE OF THE FINAL STEPS IN BEER PRODUCTION
Beer distribution
The flavour stability of lager beers random
distributed at ambient temperatures is
significantly shorter compared to other bottled
beverages
Investments by the brewing industry are necessary
a fresh beer with a good drinkability is
preferred by the consumers
- temperature as low as possible
the brand identity has to remain constant
(fresh) during distribution

• avoid the negative impact of light

use of the correct packaging material
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Yeasts can be selected for their positive effect
on flavour stability
yeast can produce SO2 this can have a positive
effect on retarding the appearance of stale and
oxidised flavours, dependent on residual amounts
of acetaldehyde and pyruvate, indicators
of deficient fermentation
A POSITIVE ROLE FOR YEAST GROWTH AND FERMENTATION
yeast strain yeast vitality are very important
Is it really necessary to aerate the wort
prior to pitching
?
?
?
?
?
?
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A POSITIVE ROLE FOR YEAST GROWTH AND FERMENTATION

• yeast can
• reduce aldehydes
• consume mono- and dihydroxy fatty acids
• reduce FAN levels
• adsorb residual a-acids, polyphenols,

• There is a limit in the removal of
• FAN (dependent on the level and
  assimilability)
  
• aldehydes

the production of a high quality pitching wort
combined with an optimal fermentation are
crucial for flavour quality and stability of beer
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The upstream processes can have a great impact on
flavour instability of beer
Interactive partnership of brewers, malsters,
hop and barley breeders as well as constructors
is necessary
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WATER and adjuncts can be made consistently
neutral in their effect on flavour stability
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The role of hopping
Fresh hop cones are particularly rich in
phenolic anti-oxidants pro-oxidant a- and
b-acids (oxidised a-acids more pro-oxidant)
Fresh hop cones contain 1-5 of lipids, LOX
and lipases are also present
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The role of hopping
Modern drying of hops increases pro-oxidant
levels, produces fatty acid oxidation aldehydes,
trihydroxy fatty acids,
The isomerisation of a-acids during wort boiling
is really inefficient ( 50 )
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The role of hopping
Because of pro-oxidant reactions and inefficient
isomerisation during wort boiling
HIGH TECH HOPPING

• Hop polyphenols added to the brewing liquor

• Refined pre-isomerised extracts or hydrogenated
  hop products added after boiling

• Refined hop oil isolates added to beer

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MALT is the positive key factor as well as the
varying risk factor in view of flavour stability
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The role of malt
Flavour stability of lager beer is best served by
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The role of malt

• high degree of homogeneity
• complete modified endosperm

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The role of malt

• high degree of homogeneity
• complete modified endosperm

smallest gradients during kilning
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Evolution of LOX during drying ? kilning
(MOISTURE BEFORE DRYING gt 44)
LOX
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The role of malt

• high degree of homogeneity
• complete modified endosperm

smallest gradients during kilning

• low residual LOX activity

• low level of aldehydes, hydroxy fatty acids
• and TB-index

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Hydroxy acids in malt
(LOX blocked)
1.4
10.1
1.3
9.9
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Aldehydes in lager malt
Strecker degradation aldehydes 2-methylpropanal,
2- and 3-methylbutanal, methional, benzaldehyde
and phenylacetaldehyde
Fatty acid oxidation aldehydes hexanal,
trans-2-hexenal and trans-2 nonenal
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The role of malt

• high degree of homogeneity
• complete modified endosperm

smallest gradients during kilning

• low residual LOX activity

• low level of aldehydes, hydroxy fatty acids
• and TB-index

• well characterised gelatinisation profile

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Gelatinisation profile of malt
100
80
peak viscosity temperature
70
BEST PROFILE
80
60
66.1C
61.5C
50
60

• - small peak
• low peak viscosity
• low peak viscosity
• temperature

temperature (C)
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viscosity (cP)
40
30
starting gelpoint
20
20
10
0
0
0 5 10 15 20 25
30 35
time (min)
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Gelatinisation profile of malt
63C
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The role of malt

• high degree of homogeneity
• complete modified endosperm

smallest gradients during kilning

• low residual LOX activity

• low level of aldehydes, hydroxy fatty acids
• and TB-index

• well characterised gelatinisation profile

• good lautering performance

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Filtration behaviour of malt
Influence of xylanase and b-glucanase
Conditions coarse milling, mash ratio 14,
mashing-in at 65 C, rest 60 min at 65 C, warm
filtration
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Filtration behaviour of malt
Influence of xylanase and b-glucanase
Conditions coarse milling, mash ratio 14,
mashing-in at 65 C, rest 60 min at 65 C, warm
filtration
MALT 2
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Conclusions for malt
Next to the brewing quality of malt (e.g. enzyme
content, evenly modified endosperm and sharp and
low peak viscosity during gelatinisation and a
good lautering performance)
It is recommended to evaluate also positive and
negative enzyme activities in relation to
flavour stability as well as the reducing
capacity, the heat load and the FAN content of
the malt
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The role of brewhouse operations
Flavour stability is best served by
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The role of brewhouse operations
Flavour stability is best served by
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The role of brewhouse operations
In order to obtain pitching worts with
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Wort production on laboratory scale

• Trihydroxy acids in worts produced on laboratory
• scale infusion mashing, warm filtration at 72 C

Mashing-in at 45 C, pH 5.6 5.8
86.6
46.7
Mashing-in at 63 C, pH 5.2 and tannins
19.3
19.8
LOX free to react, de novo formation of
hydroxy acids Effect of lipase-activity in
wort release of bound hydroxy acids
Trihydroxy acids in malt 10 - 11 mg/kg malt
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The concentration of trihydroxy acids in pitching
worts as function of the LOX-activity in malt
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ALDEHYDE PROFILE DURING BREWING
Aldehyde concentration (ppb)
START BOILING
END BOILING
PITCHING WORT
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Wort (EPR) signal intensity at the constant time
of 150 min (T150) point versus brewkettle boiling
times at different pressures and temperatures
5.0 psig (104.7 C)
2.5 psig (100.4 C)
0.0 psig (95.5 C)
Foster et al, MBAA TQ, 42, 3, 209-213, 2005
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Conclusions for brewing operations

• Critical points
• - milling and mashing-in ( 63 C, pH 5.2)
• - high radical scavenging power at mashing-in
• - restricted O2 entrainment
• - sparging
• - stripping of unwanted volatiles
• - clear worts
• - de-intensified wort boiling
• - hot wort clarification

(risk of accumulation of carbonyls)
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PROPOSAL FOR ENHANCED FLAVOUR STABILITY AND
TOTAL COST REDUCTION INNOVATIVE BREWING LINE
WITH THINBED FILTER
? ?
(7)
steam
? ?
(7)
MALT
(1)
cooling
steam
CO2
Fine Milling
99C
cooling
stripping
(4) steam
(3)
(3)
P
stripping
(3)
(3)
(2)
(5)
cooling
low shear pumps
composed brewing liquor to hydrate and mash-in at
65C, pH 5.2
(6)
iso-a-acids
(4) In line steam sparging. (5) Stainless steel
strainer with compactation device. (6) Addition
of refined, pre-isomerised extracts.
(7) Over-dimensioned condensate
traps.
(1) Very fine milling, CO2-protected grist
storage. (2) Pre-masher acting like a
stripping device. (3) Direct, clean
steam injection.
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INNOVATIVE EXPERIMENTAL BREWING LINE

• The whole set-up can be easily up-scaled, is
  based on proven technology and obviously is a
  very simple way of producing high gravity wort in
  16 brews/day with one mash vessel, a filter and
  one combination tank
• The whole operation from green beer to
  colloidally stable beer will be done in the
  shortest time and ideally without the need of
  deep cooling and final pasteurisation of bottled
  beers

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THE CRITICAL POINTS OF THIS PROCESS CONCEPT AND
STRATEGY ARE

• The success depends on the intrinsic lauter
  performance of malt and the presence of microbial
  enzymes, to be produced inside maltings in and on
  malt, such as xylanases and glucanases that still
  are active at 65 C
• Denaturation and coagulation are possible in
  mashes heated to gt 95 C, but the critical point
  appears to be flocculation
• In a process whereby O2 entrainment is
  restricted, the polymerisation of polyphenols
  might be insufficient to facilitate flock
  formation with coagulated proteins
• Mash separation at 95 C might result in sweet
  worts with a relatively high trub content

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PRACTICAL RELEVANCE

• The new brewing line, aside a traditional
  lautertun brewing line with separate vessels for
  wort boiling and hot wort clarification, offers
  opportunities to examine the effect of many
  process factors
• There also is the possibility to compare the
  effect of fine milling and coarse milling on the
  opportunities that can be exploited
• Idem to study the optimisation of the mashing
  process
• Idem to compare conventional wort boiling to
  de-intensified wort boiling and (or) wort heating

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WITH SPECIAL THANKS TO

• Brenda, Gert and Marjan
• for the technical assistance
• to realise this lecture
• Annemie, Barbara, Evelien, Filip, Ilse,
• Jan, Jessika, Koen, Luc, Silke, Sofie
• IT IS NICE
  TO WORK WITH YOU