Cactus pear (Opuntia ficus indica) flavour constituents—chiral evaluation (MDGC–MS) and isotope ratio (HRGC–IRMS) analysis

Among the volatiles isolated by solvent extraction from cactus pear fruit ( Opuntia ficus indica ) and identified by HRGC–MS, selected chiral and achiral constituents were characterized by enantiodifferentiation and 13 C/ 12 C isotope ratio analysis, using multidimensional gas chromatography–mass spectrometry (MDGC–MS) and on‐line gas chromatography–combustion isotope ratio mass spectrometry (HRGC‐C‐IRMS), respectively. While the enantiodistributions determined for methyl 2‐methylbutanoate (98 : 2%, S : R ), methyl 3‐hydroxybutanoate (73 : 27%, R : S ), 1‐phenyl‐ethanol (74 : 26%, R : S ), linalool (68 : 32%, R : S ), γ‐nonalactone (65 : 35%, S : R ), γ‐deca‐lactone (79 : 21%, R : S ) and γ‐dodecalactone (>99% R ) can be discussed in relation to data previously provided for these compounds from various plant origins, the δ 13 C values of −22.0‰, −21.8‰, −19.1‰ and −20.9‰, measured for 1‐hexanol, E ‐2‐hexenol, E ‐2‐nonenol and E , Z ‐2,6‐nonadienol, respectively, are clear‐cut indicators for their origin from plants with Crassulaceae acid metabolism (CAM), and thus may helpful for authenticity evaluations.