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Impact of dry hopping at different stages of fermentation on the physical and organoleptic quality of beer

Authors:
Maria Eleni Moutsoglou at Molson Coors Beverage Company
Maria Eleni Moutsoglou
  • Molson Coors Beverage Company
William F Cayler
William F Cayler
William F Cayler
  • This person is not on ResearchGate, or hasn't claimed this research yet.
Andrew R. Reyes
Andrew R. Reyes
Andrew R. Reyes
  • This person is not on ResearchGate, or hasn't claimed this research yet.
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Abstract

Dry-hopping is a process where hops are added to a fermenter, typically during fermentation, cooling, or after the tank has been cooled. Previous studies have shown the complexity of hop aroma derived from dry-hopping can be influenced by the biotransformative properties of yeast, where yeast-derived enzymes hydrolyze hop-derived glycosides. Additional yeast/hop interactions could influence yeast fermentation performance, potentially altering fermentation-derived flavor compounds. This study focused on the relationship between dry-hopping at different stages during fermentation and yeast fermentation performance, the organoleptic profile of the finished beer, and beer haze potential. Three stages for dry-hop additions were selected, in addition, to a control beer without dry-hopping: dry-hopping during wort pump-in (warm), late fermentation into tank chilling (warm-to-cold), and after tank cooling (cold). Fermentation time, carbohydrate utilization, cell growth, flocculation rates, VDK reduction time, and attenuation were used as metrics to assess fermentation performance. Volatile compound profiles on beers were determined using headspace gas chromatography. Quantitative descriptive analysis was performed using a trained panel. Haze potential was assessed by quantifying polyphenols, tannins, and sensitive proteins. Multivariate analysis was used to determine correlations between the investigated variables to overall beer quality. The results of this study suggest dry-hopping addition time can have a significant influence on the physical and organoleptic qualities of beer.
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impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
Impact of dry hopping at different
stages of fermentation on the
physical and organoleptic quality of beer
Maria E. Moutsoglou, Ph.D.
and
William F. Cayler
Sierra Nevada Brewing Company
Hops III | (Tuesday, August 14, 8-8:25 AM)
2
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
ACKNOWLEDGEMENTS
•Andrew Reyes provided discussions and guidance on hop-derived
compounds and biotransformation, and conducted the GCMS
volatile profile and data analysis
•Meghan Peltz and the Sierra Nevada Sensory team provided
quantitative descriptive panel assessment and data analysis
•Jon Meyerson coordinated wort procurement, cellaring, and
packaging
•Sierra Nevada Quality Assurance—Analytical Lab team provided
support with Beer Alcolyzer analysis
3
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
•does dry hopping influence the physical stability of beer?
•discussions in the brewing community have recently alluded to impact on physical
stability by early dry hopping additions
•can we further expand the flavor of hops by modulating yeast/hop interactions with
respect to hop addition time?
•can we achieve different flavor profiles/beers using the same hop variety and same
addition concentration by modulating addition time?
•can excess hops be used as a differentiating ingredient?
•can we develop unique brands or differentiate between brands with the same
“recipe”?
•with these questions in mind, we investigated how dry hopping addition time affects
various parameters of brewing and beer quality
•i.e. fermentation, physical stability, organoleptic qualities
INTRODUCTION
4
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
EXPERIMENTAL DESIGN
5
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
0 2 4 6 8 10
4
5
6
7
8
9
10
11
12
13
14
30
40
50
60
70
80
Time (days)
Real Extract (°P)
Fermenter Temperature (°F)
Dry hopping:
Whole cone Cascade
hops (2017)in sterile
weighted cheesecloth
Added from top of tank
Concentration = 3.3 g
hops/L (0.9 lb / BBL)
Yeast/Fermentation:
Strain = S. cerevisiae
(house ale/Chico yeast)
Pitch rate = 0.5 x107
cells/mL/ºP
Temperaturepump in =68ºF
Temperaturefree rise =72ºF
Temperaturechill =40ºF
experimental design: dry hopping regime
control
no
dry
hop
fermenter
full
tadd =
0 days
Tadd =
68ºF
warm to
cold
tadd =
4 days
Tadd =
72ºF
cold
tadd ~
8 days
Tadd =
40ºF
same production wort pump-in
Wort:
OG =13.3ºP
Volume total = 45 L
wort pH = 5.2
wort dissolved oxygen
= 8.5 mg/L
% wort RDF ~67%
Color = 12 |BU =41
Packaging:
Total fermenter residence
time ~ 10 days for all beers
2.50 volumes CO2/ L beer in
19 L kegs
Stored at 33ºF
replicated three times (n = 3)
fermenter full (10
days in fermenter) warm to cold (6 days
in fermenter) cold (24 hours in
fermenter)
6
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
experimental design: data collection
replicated three times (n = 3)
fit to modified Hill plot
fit to Gaussian
distribution
FERMENTATION PERFORMANCE
Daily real extract, % ABV, pH, cells density, viability
Metrics to assess statistical differences in performance:
•maximum rate of carbohydrate utilization rate (ºP/day)
•maximum rate of ethanol production (%ABV/day)
•midpoint in carbohydrate utilization (days)
•midpoint in ethanol production (days)
•maximum rate of cell growth (cells x107mL-1 days-1)
•time to begin flocculation (days)
7
0 2 4 6 8 10
0
1
2
3
4
5
Time (days)
Cells in Suspsension
x107 (cells/mL)
0 2 4 6 8 10
4
5
6
7
8
9
10
11
12
13
14
Time (days)
Real Extract (°P)
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
experimental design: data collection
repeated three times (n = 3)
PHYSICAL STABILITY
Packaged beer:
•total polyphenols (mg/L gallic acid)
•sensitive proteins (EBC after 10 mg/L gallic
tannin)
•tannins (PVP mg/L @ max EBC)
•Chapon (chill haze EBC)
ORGANOLEPTIC QUALITY
Packaged beer:
•quantitative descriptive analysis using a
trained panel
VOLATILE PROFILE ANALYSIS
Packaged beer:
•targeted semi-quantitative SPME GCMS STATISTICAL ANALYSIS
Significance determined:
•One-way ANOVA (α = 0.05)
•post-hoc Tukey’s range test
Multivariate analysis:
•Principle component analysis
•Hierarchical cluster analysis
ELEMENTAL ANALYSIS
Packaged beer:
quantitative ICP-OES
assess beer quality impact from dry hop addition time
8
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
RESULTS
9
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
experimental design: data collection
replicated three times (n = 3)
fit to modified Hill plot
fit to Gaussian
distribution
FERMENTATION PERFORMANCE
Daily real extract, % ABV, pH, cells density, viability
Metrics to assess statistical differences in performance:
•maximum carbohydrate utilization rate (ºP/day)
•maximum ethanol production (%ABV/day)
•midpoint in carbohydrate utilization (days)
•midpoint in ethanol production (days)
•maximum rate of cell growth (cells x107mL-1 days-1)
•time to begin flocculation (days)
no significant differences found in fermentation metrics
borderline significant differences
found in cell growth and flocculation metrics (α < 0.10)
10
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
experimental design: data collection
repeated three times (n = 3)
PHYSICAL STABILITY
Packaged beer:
•total polyphenols (mg/L gallic acid)
•sensitive proteins (EBC after 10 mg/L gallic
tannin)
•tannins (PVP mg/L @ max EBC)
•Chapon (chill haze EBC)
ORGANOLEPTIC QUALITY
Packaged beer:
•quantitative descriptive analysis using a
trained panel
VOLATILE PROFILE ANALYSIS
Packaged beer:
•targeted semi-quantitative SPME GCMS
STATISTICAL ANALYSIS
Significance determined:
•One-way ANOVA (α = 0.05)
•post-hoc Tukey’s range test
Multivariate analysis:
•Principle component analysis
•Hierarchical cluster analysis
ELEMENTAL ANALYSIS
Packaged beer:
quantitative ICP-OES
assess beer quality impact from dry hop addition time
11
no significant differences found
in physical stability metrics
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
significant beer quality-related metrics:
pH
average of n= 3 final beer pH
error bars represent standard deviation
α= 0.05
** *
*dry hopping in all cases acted as buffering reagent
(clamped pH at 4.5) and/or hydroxide ions (raised pH
from ~4.3 to 4.5)
12
No Hops
Warm to Cold
Fermenter Full
Cold Addition
4.1
4.2
4.3
4.4
4.5
4.6
4.7
Final Beer pH
0 2 4 6 8 10
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
5.0
5.1
5.2
5.3
Time (days)
pH
No Hops
Warm to Cold
Fermenter Full
Cold Addition
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
significant beer quality-related metrics:
% RDF under-attenuation
*
Total Density Decrease from OG
=OG - RealExtracttime
*
average of n = 3 values
error bars represent standard deviation
α = 0.05
%RDF under-attenuated =
% wort RDF - % fermenter RDF
hops imparted additional density to the wort
likely some percentage is fermentable!
13
No Hops
Warm to Cold
Fermenter Full
Cold Addition
0
1
2
3
4
5
6
% RDF
Under-attenuated
4 5 6 7 8 9 10
-8.6
-8.5
-8.4
-8.3
-8.2
-8.1
-8.0
Time (days)
Total Density Decrease
from OG (ºP)
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
significant cationic elements
***
***
***
**
****
****
*
average of n= 3 values
error bars represent standard deviation
α= 0.05
dry hopping universally increased Mg, K,
and Mn in the finished beer
**
***
***
14
No Hops
Warm to Cold
Fermenter Full
Cold Addition
0.0
0.1
0.2
0.3
0.4
Manganese (mg/L)
No Hops
Warm to Cold
Fermenter Full
Cold Addition
90
95
100
105
110
115
Magnesium (mg/L)
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
significant organoleptic qualities
quantitative descriptive panel assessment:
n ~ 8 trained panelists per screening
rated intensity from 0 to 8 (8 = most intense)
average of intensity ratings
from n= 3 panels
α= 0.05 15
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
quantitative descriptive
panel assessment
No Hops Fermenter Full Warm to Cold Cold p value
Malty/Bready 3.5 A2.4 B2.5 B2.2B0.006
Overall Hop Intensity 2.8 B4.1 A4.0 A4.1A<0.001
Citrus 2.2 B3.1 A3.1A2.1 B<0.001
Rose/Floral 2.0 BC3.2 A2.7 AB1.4 B0.001
Fruity/Tropical 1.6 D3.9A3.0 B2.0C< 0.0001
Catty 1.0 C2.0 B2.2 AB3.1 A0.001
Skunky/Dank 1.3 B1.3 B1.5 B4.5A< 0.0001
Onion/Sulfur 2.2A B1.5 B1.8B3.1 A0.014
Burnt Rubber 1.6 AB0.7 B0.7B2.2 A0.025
Bitter 2.7 2.9 2.7 3.1 0.266
Harsh 1.7 1.7 1.8 2.2 0.160
quantitative descriptive panel assessment:
n ~ 8 trained panelists per screening
rated intensity from 0 to 8 (8 = most intense)
significance determined using one-way ANOVA for
panel results from three separate trials (α = 0.05)
typical Cascade hop descriptor: pine, citrus, floral
16
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
multivariate analysis:
hierarchical cluster
•more furans remaining in un-
hopped beer = malty/bready
•more fermentation esters
methyl
mercaptan
significantly
higher in cold
addition = onion
sulfur and burnt
rubber
neryl/geranyl
acetate and geranyl
propionate is
higher in cold hop
suggests some impact
on fermentation early dry
hopping
compounds/variables higher when dry hopping in the presence of yeast
two way hierarchical cluster analysis performed using Ward’s method on variables showing significance with one-way ANOVA
red = high value, blue = low value 17
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
multivariate analysis:
principal components
positive correlation to
component 1 = dry
hopping in the presence
of yeast
positive correlation to
component 2 = cold dry
hopping
18
PCA performed on variables showing
significance with one-way ANOVA
III
III IV
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
multivariate
analysis:
PCA
hop addition
time
•warm to cold and fermenter full hop
additions are grouped close
together—but fermenter full addition
shows stronger negative correlation
to component 2
•cold dry hopping in the absence of
yeast is distinct—not positively
correlated to component 1 and
showing positive correlation to
component 2
19
no hops
fermenter full
warm to cold
cold
III
III IV
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
high concentrations of
monoterpene alcohols
(geraniol, linalool, nerol)
high sensory ratings for
rose/floral, fruity tropical,
citrus
high concentrations
of hop-derived esters
high concentration
of furans
high concentration
of fermentation-
derived esters
high sensory rating
for skunky/dank
high sensory rating
for catty
high sensory rating
for malty/bready
high sensory rating for
overall hop intensity
high concentration of (potential)
fermentation-derived esters
COLD
WARM
TO COLD
FERMENTER
FULL
no dry
hops
multivariate
analysis:
PCA
hop addition
time
20
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
SUMMARY/CONCLUSIONS
21
impact of dry-hopping at different fermentation stages on beer quality | MEM, WFC | August 14, 2018 | JBC 2018
modulate hop-derived flavor by addition time
•does dry hopping influence the physical stability of beer?
•no effect on polyphenols, tannins, sensitive proteins
•can we further expand the flavor of hops by modulating yeast/hop interaction with respect to hop
addition time?
•can we achieve different flavor profiles using the same hop variety and same addition
concentration?
•yes—flavor from dry hopping with the same addition concentration/hop variety can change
depending on addition time and the presence/absence of yeast
•can unique or desirable hop-derived flavor be obtained using excess hops by modulating dry hop
timing?
•can we develop unique brands or differentiate between brands with the same “recipe”?
•the potential is there—further investigation is required to understand hop-dependent
interaction with yeast, and the transformation/formation of volatile compounds during
fermentation
•assess potential for other hops and other yeast—effect may be more dramatic or muted
22
... The addition of hops can further contribute to flavor complexity, as well as provide additional precursors for biotransformation reactions by the yeast. For beers with a strong hop aroma, such as pale ales and IPAs, hop oils are transferred to the beer by addition of hops at a stage in the process post boiling (Moutsoglou and Cayler, 2018). Dry hopping is the process of adding hops to green beer, either during the fermentation phase or during maturation. ...
... Hop varieties used normally for beer styles such as IPA or NEIPA can also be used for fruity aromatic ciders without increasing bitterness. The timing of hop additions in beer has been proven to significantly influence the aroma profile, and this effect is likely to be important in cider as well, making it essential to include in future studies (Moutsoglou and Cayler, 2018). Future work could also include further selection of yeasts, incorporating other alternative yeasts, a focus on precursors, timing of hopping and other conditions that have proved to be important in other beverages. ...
View
Fruits of their labour: biotransformation reactions of yeasts during brewery fermentation
Article
Full-text available
  • Aug 2022
  • APPL MICROBIOL BIOT
There is a growing appreciation for the role that yeast play in biotransformation of flavour compounds during beverage fermentations. This is particularly the case for brewing due to the continued popularity of aromatic beers produced via the dry-hopping process. Here, we review the current literature pertaining to biotransformation reactions mediated by fermentative yeasts. These reactions are diverse and include the liberation of thiols from cysteine or glutathione-bound adducts, as well as the release of glycosidically bound terpene alcohols. These changes serve generally to increase the fruit and floral aromas in beverages. This is particularly the case for the thiol compounds released via yeast β-lyase activity due to their low flavour thresholds. The role of yeast β-glucosidases in increasing terpene alcohols is less clear, at least with respect to fermentation of brewer’s wort. Yeast acetyl transferase and acetate esterase also have an impact on the quality and perceptibility of flavour compounds. Isomerization and reduction reactions, e.g. the conversion of geraniol (rose) to β-citronellol (citrus), also have potential to alter significantly flavour profiles. A greater understanding of biotransformation reactions is expected to not only facilitate greater control of beverage flavour profiles, but also to allow for more efficient exploitation of raw materials and thereby greater process sustainability. Key points • Yeast can alter and boost grape- and hop-derived flavour compounds in wine and beer • β-lyase activity can release fruit-flavoured thiols with low flavour thresholds • Floral and citrus-flavoured terpene alcohols can be released or interconverted
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Piecing Together What We Know and What We Don’t on Biotransformation and Its Organoleptic Impact
Article
  • Sep 2021
Biotransformation has become a buzzword within the brewing community, with many brewers swearing by dry hopping during active fermentation to encourage it. In this review, we aim to cover the academic literature on this topic and attempt to elucidate if biotransformation is the main driving force behind the observed sensory changes of different dry hop timings or if other physical, biological, or chemical processes take a lead role. When the potential sensory impact of each biotransformation pathway is considered, we argue that only thiol release and potentially esterification (although more studies are still required to ascertain its contribution) could have a marked effect, with other causes, such as CO2 scrubbing and yeast binding, having an influence not normally recognized.
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