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Foods, Flavours and Fragrances Applications 223

Figure 10.2 MDGC–MS differentiation between the enantiomers of theaspiranes in an
aglycone fraction from purple passion fruit: DB5 pre-column (25 m 0.25 mm i.d., 0.25 m
film thickness; carrier gas He, 0.66 ml/min; oven temperature, 60–300 °C at 10 °C/min with
a final hold of 25 min); permethylated -cyclodextrin column (25 m 0.25 mm i.d., 0.25 m
film thickness; carrier gas He, 1.96 ml/min; 80 °C isothermal for 20 min and then pro-
grammed to 220 °C at 2 °C/min). Reprinted from Journal of High Resolution Chromato-
graphy, 16, G. Full et al., ‘MDGC–MS: a powerful tool for enantioselective flavor analysis’,
pp. 642–644, 1993, with permission from Wiley-VCH.

automated multiple transfers, because retention times on the pre-column were repro-
ducible even for those components eluted after numerous transfers. Moreover, when
the MDGC system was not used, the two chromatographs can be operated indepen-
dently without any hardware modification. Figure 10.3 shows chromatograms of a
cold pressed lemon oil obtained with an SE-52 pre-column and the system in the
stand-by position, the same oil obtained with the SE-52 column and the system in
the cut position, and that obtained with the chiral column (modified -cyclodextrin)
for the fractions transferred from the pre-column.
Table 10.2 reports some results obtained for cold-pressed and distilled citrus oils.
As can be seen, the values obtained are characteristic of the different oils, and can be
used as references for the authenticity and quality of the oil.
In recent years, together with enantioselective analysis, the determination of the
natural abundance of stable isotopes by means of stable isotope ratio mass spectrom-
etry (IRMS) can be very useful for the assignment of the origin of foods and food
ingredients, and of authenticity evaluation (24).