2.2.
SPME-GC-MS
analysis
Gas-chromatography
(GC)
combined
with
mass
spectrometer
detector
(Agilent
5975C
Series
GC
Inert
MSD,
Agilent
Technologies),
equipped
with
an autosampler
(Multipurpose
Sampler,
GERSTEL
GmbH
& Co.
KG)
was
used
to analyse
the
vapour
phase
of
all
the
off-flavoured
chocolate
samples
and
some
of
the
standard
samples.
Sampling
of
the
volatile
compounds
was
performed
by solid
phase
micro-extraction
(SPME).
For
each
analysis
about
5 g of
choco-
late
were
cut
in small
pieces
and
1 g was
taken
and
inserted
in a
20
ml-vial
that
was
closed
with
crimp
top
caps
and
rubber
septa.
The
sample
was
kept
for
10
min
at
40◦C and
then
exposed
to the
fiber
(StableFlexTM, 50/30UM
DVB/CARBOXEN-PD,
Sigma-Aldrich
Co.)
for
30
min
at
fixed
temperature.
The
fiber
was
inserted
in the
desorption
chamber
where
GC
analysis
was
carried
out
with
the
fol-
lowing
temperature
gradient:
the
column
was
kept
7 min
at
40◦C
then
the
temperature
was
raised
up to 220◦C at
16◦C/min
and
then
kept
at
220◦C for
8 min.
The
column
used
was
a
Stabilwax®Column
(Restek
Corporation
• 110
Benner
Circle
• Bellefonte,
PA)
(lenght
30
m;
internal
diameter
0.25
mm;
film
thickness
0.50
?m).
Chro-
matograms
obtained
were
analysed
and
compounds
were
assumed
to
be
identified
for
matching
higher
than
70%
in the
mass
spectrom-
eter
library.