2
Table of Contents
Introduction
....................................
2
Analysis of Alcohols and Aldehydes in
Alcoholic Beverages
....................................
2
Flavor Compounds in Distilled
Liquor Products
............................................
4
Determining Trace Sulfur Compounds
in Beer
..........................................................
8
Summary
....................................................
10
Products
................................................
11-16
Rtx
®
-1301 Columns ....................................11
Stabilwax
®
-DAColumns..............................11
CarboBlack
™
BColumns..............................11
Leak Detective
™
II Leak Detector..................11
Rt-XLSulfur
™
Micropacked Columns ..........12
Sample Vials ..............................................12
Syringes......................................................13
Inlet Liners..................................................14
Vespel
®
Ring Inlet Seals..............................15
Inlet Seals ..................................................15
FID Jets ......................................................16
Introduction
The volatile component profiles of alcoholic beverage products consist of awide range of
compounds, including acids, alcohols, aldehydes, andother trace level flavor compounds.
Analysts trained in the sensory evaluation of distilled liquors, wines, or beers tell us no
two products are exactly alike. The unique sensory properties of different types and
brands of distilled liquor products often are due tominor differences among the volatile
components present. By using instrumental methods for qualitatively or quantitatively
evaluating these differences, in addition to sensory techniques, quality assurance analysts
can obtain awealth of information about their products.
In addition to alcohols and flavor compounds, impurities such as sulfur gases occasional-
ly are present, andmight lead to off odors or flavors in the product. Because even parts
per billion (ppb) levels of sulfur compounds can impact product quality, a sensitive and
selective method of analysis is needed to detect these impurities. The majority of these
contaminants are present in the gas phase, necessitating a gas phase sampling and analy-
sis system. Because sulfur compounds also can be very reactive, an inert analysis system
is highly desirable.
Gas chromatography (GC) is a powerful tool in the analysis of alcoholic beverage prod-
ucts.Minimal sample preparation, ingeneral, is required, since the samples are in the liq-
uid state in an alcohol or alcohol/watermatrix. The flavor compounds tend to be volatile
in nature, which fulfills one of themain requirements of GC. General detectors, such as
the flame ionization detector (FID), ormore information-rich detectors, such as themass
selective detector (MSD), can be used. Additionally, the ability to automate the analysis
makes GC a very practical tool in a QA/QC environment. In this guide, we will discuss
howGC can be used to (1)monitor alcohol content in alcoholic beverages, (2) determine
the volatile profile of a product, and (3) detect trace level impurities.
Analysis of Alcohols and Aldehydes in Alcoholic Beverages
Alcoholic beverages contain awide range of volatile compounds, including alcohols and
short-chain aldehydes. Gas chromatography can be used to analyze these compounds
without preliminaryextractions. For example,AOAC International haspublishedmethods
for the analysis of fusel oils, methanol, ethanol, and higher alcohols by GC.
1
Traditionally, packed columns prepared from glass tubing have been used for alcoholic
beverage analysis, but these are prone tobreakage and can adsorb some of themore reac-
tive compounds. Restek's Silcosteel
®
-treatedCarboBlack
™
columns aremade from stain-
less steel which has been treated to provide it with a deactivated silica surface. This con-
ditioning significantly improves inertness and flexibility, relative to traditional glass
packed columns.
CarboBlack
™
packed columns can be used to quantify the various alcohols in alcoholic
beverages. For example, ethanol can be monitored to determine the proof value of the
beverage, while methanol and isopropanol can be quantified to determine the levels of
denaturantspresent.
2
Whilepoormethanol peak shapesoftenareassociatedwithcolumns
of limited sample capacity, a CarboBlack
™
B packed column with 5%Carbowax
®
20M
provides an excellent peak shape for methanol, and completely resolves methanol from
ethanol, as shown in Figure 1. In addition, the two predominant fusel oils, active amyl
alcohol and isoamyl alcohol, can be resolved andmonitored by using this column.
Alcohols and aldehydes in alcoholic beverages also can be monitored by capillary GC.
Since capillary columns offer efficient separations, capillary GC is especially useful in
analyses of structurally similar compounds, such as the fusel alcohols.The unique polari-
ty of the Rtx
®
-1301 stationary phase ensures excellent resolution of a range of alcohols
and fusel oils.An example of a rum analysis is shown in Figure 2.
Fusel Alcohols
Fusel alcohols are higher-order (i.e.,
secondary or tertiary) alcohols, traces
of which usually are present in all
beers. They are produced through a
pathway very similar to the pathway
for ethanol, the preferred alcohol of
beer. Fusel alcohols contribute a hot,
spicy, solvent-like flavor and an alco-
hol "burn". Small amounts of these
components can be desirable in a
strong ale or barley wine, but they can
be offensive, and therefore are
unwanted, inaPilsner or other lager. In
addition to their influence on flavor,
they usually cause low carbonation
and poor head retention in bottle-con-
ditioned beers, because they are dead-
ly to yeast. Higher fermentation tem-
peratures can produce excessively
rapid yeast growth, and yeast muta-
tions, which, in turn, stimulate the for-
mation of these components.
