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Tracking Chemical Changes in
Aging Beer using GC-TOFMS
Elizabeth Humston-Fulmer
Life Science and Chemical Analysis Centre
LECO Corporation, St. Joseph, MI
Outline
Objective: Investigate chemical changes related to beer aging using non-targeted discovery based tools
• Beer Aging – general background and analysis techniques
• Analytical Tools and Experimental Methods
• Review of data
Beer Aging
A complex dynamic system
• After bottling, beer continues change
• As it ages, flavors fade or appear, oxidation occurs, degradation of proteins and other molecules, continued yeast activity, etc.
Beer AgingUsually dark, malty beers with >8% ABV
Aim for consistent product that tastes
the same over the duration of shelf life
Maintain with age
Usually hop-forward beers
Beer Analysis Methods
Sensory
Panel
Trained human panel uses
senses to evaluate consumer
products
Target
Acquisition
Instrumental analysis to
screen for specific, pre-
selected analytes of interest
Non-target
Acquisition
Instrumental analysis to
acquire comprehensive data
and discover
Beer Analysis Methods
Sensory
Panel
Trained human panel uses
senses to evaluate consumer
products
Target
Acquisition
Instrumental analysis to
screen for specific, pre-
selected analytes of interest
Non-target
Acquisition
Instrumental analysis to
acquire comprehensive data
and discover
Beer Analysis Methods
Sensory
Panel
Trained human panel uses
senses to evaluate consumer
products
Target
Acquisition
Instrumental analysis to
screen for specific, pre-
selected analytes of interest
Non-target
Acquisition
Instrumental analysis to
acquire comprehensive data
and discover
Generate Time Course Samples
• Samples: Commercially available craft IPA (canned) purchased from grocery store• Sample prep: Accelerated/simulated aging with elevated temperature[1]
[1] Marques. ASBC Presentation A30. Chicago, IL. June 2014.
Packaging to analysis = 8 weeks
General Aroma Profile Sampling Method
General profiling of aroma analytes. Headspace solid phase micro-extraction (HS-SPME) concentrates volatile and semi-volatile compounds in the headspace above a sample onto a fiber
Method Details:
1) Incubate 5 mL beer for 10 min at 60˚C to
drive compounds into the gas phase
2) Expose tri-phase SPME fiber
(DVB/CAR/PDMS) to headspace for 20 min
to collect volatile analytes
3) Expose fiber to GC inlet at 250˚C for 3 min to
desorb and inject analytes for analysis
GC
Automated with LECO’s L-PAL 3 Autosampler
Various models available to perform liquid, headspace, and/or SPME injections.
• Automatic Tool Exchange to switch between injection types
• Controlled by LECO’s ChromaTOF software
• Agitator for sample heating/agitation
• Needle conditioning port
Fully automates the HS-SPME process
GC-TOFMS for Non-target acquisition
GC Agilent 7890
Column Stabilwax, 30 m x 0.25 mm i.d. x 0.25 µm coating (Restek)
Carrier Gas He @ 1 ml/min
Oven Program 4 min at 35°C, ramp 5°C/min to 180°C, ramp 10°C/min to 220°C hold 5 min
MS LECO Pegasus® BT
Ion Source Temp 250 °C
Mass Range 35-650 m/z
Acquisition Rate 10 spectra/s
• Gas chromatography (GC) to
separate individual analytes
within the complex matrix
• Time-of-flight mass spectral
(TOFMS) with full mass range
detection for identification &
quantitation
GC-TOFMS Data
Overlay of replicate injections of all time points:
0, 1, 2, 3, 4, 5, 6, 8, 12, and 20
0
1
2
3
4
5
6
8
12
20
“Sensory”
Observations
Target Analysis
0
1
2
3
4
5
6
8
12
20
Esters ethyl acetate and isobutyl acetate
Terpenes humulene and β-myrcene
Terpenoids linalool and geraniol
Ketone diacetyl
Sulfur dimethyl disulfide
Ester: ethyl acetate
0
1
2
3
4
5
6
8
12
20
Odor: ethereal, fruity, sweet, weedy,
and green
TIC
m/z 61.03
Target Analysis
0
1
2
3
4
5
6
8
12
20
Esters ethyl acetate and isobutyl acetate
Terpenes humulene and β-myrcene
Terpenoids linalool and geraniol
Ketone diacetyl
Sulfur dimethyl disulfide
Non-target Analysis
General peak finding and deconvolution provide information on hundreds of analytes:
1) Compile peak area information for 317 analytes Esters, terpenes, terpenoids, alcohols, aldehydes/ketones, sulfur containing, heterocyclic
2) Search for differences and trends with t-test (time 0 vs time 20) and regression statistics108 significantly differ at 95% confidence and exhibit a time course trend based on R2
3) Group analytes that trend up or down based on slopes50 increase and 58 decrease
Non-target Analysis
0 1 2 3 4 5 6 8 12 20
Summary of analytes that change:
Each row is an analyte and each column is a
time point. Color scale shows relative
intensity.
• Blue/green to yellow – increase
• Yellow to blue/green – decrease
Non-target Analysis
0 1 2 3 4 5 6 8 12 20
Esters ethyl acetate and isobutyl acetate
Terpenes humulene and β-myrcene
Terpenoids linalool and geraniol
Ketone diacetyl
Sulfur dimethyl disulfide
Non-target Analysis
m/z 93.08
herbal, fresh, camphor, sweet, pine, earthy, woody0 1 2 3 4 5 6 8 12 20
*
Ester decreases
1212 1214 1216 1218 1220 1222 1224
0
1e6
2e6
3e6
4e6
Time (s)
XIC(89.06±0.05) a0A XIC(89.06±0.05) a0A_2
m/z 89.06
Oily, green, waxy, soapy, clean, fruity, creamy0 1 2 3 4 5 6 8 12 20
*
More Information
Much more information present in data
- Analytes that change
- Analytes that are consistent
0 1 2 3 4 5 6 8 12 20
Summary
GC-TOFMS is a non-targeted analytical technique that provides comprehensive data that can be mined for specific target analytes of interest and also reviewed for inherent trends and differences in the data without specifying target analytes in advance of acquisition for discovery analyses
For More Information
Contact LECO at:
World Headquarters/United States
In United States: 800-292-6141 or 269-985-5496
Outside U.S.A.: 269-983-5531
Email: [email protected]
www.leco.com