347
tures of phenolic compounds present in wine and grape using C18 column, UV/Vis
diode-array detector, and a binary solvent system with an acidified polar solvent
such as aqueous solution of acetic, perchloric, phosphoric, or formic acids (solvent
A) and a possibly acidified organic modifier such as methanol or acetonitrile (solvent B). Phenolic compounds show characteristic absorbances in the UV/Vis region:
anthocyanins have an absorbance maximum around 520 nm, flavonols around
360 nm, and hydroxycinnamic acids at 320 nm. Flavan-3-ols can be detected at
280 nm, and these substances have fluorescence properties that the other wine polyphenols do not. Liquid chromatography coupled to mass spectrometry, as a sophisticated technique, has been used for the characterization of phenolic compounds in
wine samples that allows a variety of phenolic structures to be identified (Ivanova
et al. 2011a).
Gas chromatography (GC) is used widely in applications involving food analysis. Typical applications pertain to the quantitative and/or qualitative analysis of
food composition, natural products, food additives, flavor and aroma components, a
variety of transformation products, and contaminants, such as pesticides, fumigants,
environmental pollutants, natural toxins, veterinary drugs, and packaging materials
(Lehotay 2002). Typically, GC is useful for analyzing nonpolar and semipolar, volatile and semi-volatile chemicals. Without chemical derivatization, GC is often used
for the analysis of sterols, oils, low-chain fatty acids, aroma components and offflavors, and many contaminants, such as pesticides, industrial pollutants, and certain
types of drugs in foods.
Separation of the components from the mixture by gas chromatography (GC) is
based on the difference in the partition coefficients between the stationary liquid
and mobile gas phases. The basic principal of gas chromatography is that the greater
the affinity of the compound for the stationary phase, the more the compound will
be retained by the column and the longer it will be before it is eluted and detected.
Thus the heart of the gas chromatograph is the column in which separation of the
component takes place, and to this must be added the source and control of the carrier gas flow through the column, a means of sample introduction and a means of
detection of the components as they elute from the end of the column. Since temperature will influence the volatility of the analytes, the column is placed in a thermostatically controlled oven.
Gas chromatography (GC) is a technique most commonly used in combination
with mass spectrometry (MS), and if it is used for product identification (under very
controlled conditions), it must be directly coupled to a mass spectrometer when
information other than a comparative fingerprint (program) is required, such as
positive identification of peaks on the chromatogram. Complex mixtures can be
very easily separated by gas chromatography, and MS is used to identify individual
components, because the mass spectrum provides information about their structure.
The individual components of the mixture appear on the gas chromatogram in the
form of separate peaks. Retention time can serve as a quantity for qualitative definition, but this is not a reliable way, so it should in no way be used to determine the
composition of unknown and previously unidentified compounds.
11 Chemical Composition and Nutritional Properties of Functional Food
tures of phenolic compounds present in wine and grape using C18 column, UV/Vis
diode-array detector, and a binary solvent system with an acidified polar solvent
such as aqueous solution of acetic, perchloric, phosphoric, or formic acids (solvent
A) and a possibly acidified organic modifier such as methanol or acetonitrile (solvent B). Phenolic compounds show characteristic absorbances in the UV/Vis region:
anthocyanins have an absorbance maximum around 520 nm, flavonols around
360 nm, and hydroxycinnamic acids at 320 nm. Flavan-3-ols can be detected at
280 nm, and these substances have fluorescence properties that the other wine polyphenols do not. Liquid chromatography coupled to mass spectrometry, as a sophisticated technique, has been used for the characterization of phenolic compounds in
wine samples that allows a variety of phenolic structures to be identified (Ivanova
et al. 2011a).
Gas chromatography (GC) is used widely in applications involving food analysis. Typical applications pertain to the quantitative and/or qualitative analysis of
food composition, natural products, food additives, flavor and aroma components, a
variety of transformation products, and contaminants, such as pesticides, fumigants,
environmental pollutants, natural toxins, veterinary drugs, and packaging materials
(Lehotay 2002). Typically, GC is useful for analyzing nonpolar and semipolar, volatile and semi-volatile chemicals. Without chemical derivatization, GC is often used
for the analysis of sterols, oils, low-chain fatty acids, aroma components and offflavors, and many contaminants, such as pesticides, industrial pollutants, and certain
types of drugs in foods.
Separation of the components from the mixture by gas chromatography (GC) is
based on the difference in the partition coefficients between the stationary liquid
and mobile gas phases. The basic principal of gas chromatography is that the greater
the affinity of the compound for the stationary phase, the more the compound will
be retained by the column and the longer it will be before it is eluted and detected.
Thus the heart of the gas chromatograph is the column in which separation of the
component takes place, and to this must be added the source and control of the carrier gas flow through the column, a means of sample introduction and a means of
detection of the components as they elute from the end of the column. Since temperature will influence the volatility of the analytes, the column is placed in a thermostatically controlled oven.
Gas chromatography (GC) is a technique most commonly used in combination
with mass spectrometry (MS), and if it is used for product identification (under very
controlled conditions), it must be directly coupled to a mass spectrometer when
information other than a comparative fingerprint (program) is required, such as
positive identification of peaks on the chromatogram. Complex mixtures can be
very easily separated by gas chromatography, and MS is used to identify individual
components, because the mass spectrum provides information about their structure.
The individual components of the mixture appear on the gas chromatogram in the
form of separate peaks. Retention time can serve as a quantity for qualitative definition, but this is not a reliable way, so it should in no way be used to determine the
composition of unknown and previously unidentified compounds.
11 Chemical Composition and Nutritional Properties of Functional Food