Food& Flavor
Applications
note
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#59546
Food& Flavor
GCAnalysisof Chiral Flavor Compounds inApple JuicesUsing the
Rt-
β
DEXsm
™
andRt-
β
DEXse
™
Columns
The fruitmarket has been estimated at over $12billionper year
in theU.S., and the incidence of adulterated/mislabeled juices is
at least 10%, costingover $1billionper year.
1
This small
percentagemeans that sugar, color, organic acids,minerals, and
flavors are being sold either partiallyorwholly inplace of the
juice.
2
Manynatural flavoringmaterials aremuchmore expen-
sive toproduce than the corresponding artificialmaterials and
they commandmuchhigher prices.
3
Many flavor constituents are chiral compounds that usually exist
as onepredominant enantiomer innature;whereas those from a
synthetic originoftenoccur as a racemicmixture. Chiral gas
chromatography (GC),whichdetermines enantiomer ratio, is a
goodmethod todetect synthetic adulterants. Ethyl-2-
methylbutyrateand2-methylbutyrateare important constituents
Figure1
Enantiomeric resolution of racemic ethyl-2-methylbutyrate and 2-methylbutyrate is achieved on
Rt-
β
DEXsm
™
andRt-
β
DEXse
™
columns.
30m, 0.32mm ID, 0.25µm a) Rt-
β
DEXsm
™
and b) Rt-
β
DEXse
™
columns (cat.#’s 13104 and 13106). 10µL direct injection;
Oven temp.:
40°C (hold 1min.) to 220°C@ 2°C/min.;
Inj. & det. temp.:
220°C;
Carrier gas:
hydrogen@ 80cm/sec.
min. 6
8
10
12
contributing to apple flavor, andboth arenaturallypredominant
as the (S) isomer in apple juices.
3
Analysis of apple essence on
modified cyclodextrin chiral columns candetect additions of
syntheticethyl-2-methylbutyrate.
4
TheRt-
β
DEXsm
™
column
(2,3-di-
O
-methyl-6-
O
-
tert
-butyldimethylsilyl-
β
-cyclodextrin)
and theRt-
β
DEXse
™
column (2,3-di-
O
-ethyl-6-
O
-
tert
-
butyldimethylsilyl-
β
-cyclodextrin) can separate theenantiomers
of 2-methylbutyrateandethyl-2-methylbutyrate (Figure1). In
addition, theRt-
β
DEXsm
™
column also can resolve theoptical
isomers of 2-methylbutyric acid, a chiral acid that is used in
significant quantities as a flavor substance.
5
The enantiomers are
notwell resolvedon theRt-
β
DEXse
™
column (Figure2). Natural
2-methylbutyricacidhasbeen investigated inmany fruits suchas
apples, apricots, pineapples, and strawberries, and inall caseswas
found tobepresent in thealmost enantiopure (S) form.
5
min. 6
8
Figure2
Enantiomeric resolution of racemic 2-methylbutyric acid is provided by theRt-
β
DEXsm
™
column,
but not by theRt-
β
DEXse
™
column.
30m, 0.32mm ID, 0.25µm a) Rt-
β
DEXsm
™
and b) Rt-
β
DEXse
™
columns (cat.#’s 13104 and 13106). 10µL direct injection;
Oven temp.:
40°C (hold 1min.) to 220°C@ 2°C/min.;
Inj. & det. temp.:
220°C;
Carrier gas:
hydrogen@ 80cm/sec.
min.
18
20
22
min.
18
20
22
24
26
Rt-
β
DEXsm
™
Rt-
β
DEXse
™
Rt-
β
DEXsm
™
Rt-
β
DEXse
™
1 2
3
4
1 2
3 4
5
6
5
6
1. (R)-EMB
2. (S)-EMB
3. (R)-MB
4. (S)-MB
5. (S)-2-methylbutyric acid
6. (R)-2-methylbutyric acid
