Identification and Quantification of
Impurities in Wines by GC/MS
Benedicte Gauriat-Desroy, Eric Phillips, Stacy Crain, Trisa Robarge, Thermo Fisher Scientific, Austin, TX, USA
(With special thanks to members of Œnologic Center of Grezillac)
Introduction
While wine makers have historically used gas chromatography
and mass spectrometry (GC/MS) to detect pesticides, they
now more commonly use the technique to supplement
quality control checks of wine taste. Without GC/MS,
wine makers must rely on expert evaluation by oenologists
to determine wine quality. By identifying maturation tracers
and molecules commonly responsible for taste defects,
GC/MS augments expert opinion with objective and
quantitative information. When using a SPME extraction
method, GC/MS has the additional advantages of requiring
very small sample sizes, a minimum of sample preparation,
and rapid analysis of target molecules.
Several types of molecules, while not dangerous to
humans, affect wine taste and quality, such as volatile
phenol compounds derived from
Brettanomyces
yeast
metabolism.
1,2
Haloanisoles such as 2,4,6-tricholoranisole
that result from cork fungal infections also affect wine taste.
3,4
Methoxypyrazines such as 3-isobutyl-2-methoxypyrazine
(IBMP) and 3-isopropyl-2-methoxypyrazine (IPMP) are
maturation markers, and detecting their levels can help
determine ideal grape harvest time.
5
An automated technique
with repeatable results for detecting these compounds is
highly desirable, and GC/MS can provide such a method.
Extracted wine samples were analyzed by a sequential
full-scan/SIM acquisition on a GC-MS system consisting
of a Thermo Scientific ISQ single-quadrupole mass spec-
trometer and a Thermo Scientific TRACE GC Ultra gas
chromatograph. The results were compared to the sensitivity
limits of human tasters. This method allows wine makers to
obtain precise measurements on the organoleptic parameters
that determine wine purity on site rather than having to
send samples for expensive, external analysis. In this report,
we present the design and results of this study, including
the experimental method used to detect impurities and
the concentration ranges that compare GC/MS with
human detection.
Methods
For this experiment, several targeted molecule types that
affect wine quality were analyzed using an ISQ
™
Single
Quadrupole GC-MS system (Figure 1). Table 1 contains a
brief description of the effects on wine quality of the four
target molecule types, and examples of how GC/MS
analysis can provide value in quality control.
Key Words
• ISQ Single
Quadrupole GC-MS
• TRACE GC Ultra
• Food and
Beverage
• SPME
• Wine
Application
Note: 52242
Molecule Type
Description of Effect on Wine
Benefit of GC/MS Analysis
Volatile Phenols
Volatile phenols are produced in various steps
GC/MS can detect 4-ethylphenol and 4-ethylgaiacol
(4-ethylphenol, 4-ethylgaiacol,
of Brettanomyces yeast metabolism. The two
in lower concentration than human tasters. GC/MS
4-vinylphenol, 4-vinylgaiacol)
produced in the final step – 4-ethylphenol and
can also detect the presence of 4-vinylphenol and
4-ethylgaiacol – give the wine an “animal”
4-vinylgaiacol, intermediaries in Brettanomyces
taste and depreciates its quality.
yeast metabolism and allow wine makers to
discard contaminated batches.
Geosmine
This fragrant compound derived from moldy
Detecting geosmine in wine alerts makers to the
grapes interferes with a wine’s taste.
presence of mold in their grapes and allows them
to locate and treat a contaminated plot of land.
Haloanisoles (TBA, TCA, TeBA, PCA)
These compounds come from halophenols,
Assays provide information of an organoleptic
compounds used to prevent wood degradation
default in wine production and help identify
in vines. They give wine a moldy odor.
contamination sources.
Methoxypyranzines (IBMP, IPMP)
IBMP and IPMP are maturation markers, and
Determining the levels of IBMP and IPMP in wine
their levels decrease as wine matures. IBMP
affects harvesting decisions.
gives wine a “green pepper” taste; IPMP
imparts an earthy flavor.
Table 1: Targeted molecules affecting wine purity
Figure 1:
ISQ Single
Quadrupole GC-MS system
