Profiling of apple volatile compounds by solid phase microextraction and comprehensive two dimensional gas chromatography with quadrupole mass spectrometry

A previous optimized SPME-GC-MS method, developed to study apple headspace (Aprea et al., 2012), was adapted for a two-dimensional gas chromatograph based on a differential flow modulator (Agilent’s Capillary Flow Technology) coupled to a quadrupole mass spectrometer (GCxGC-MS). Two combinations of column set were tested (1: apolar–polar; 2: polar-apolar). Volatile compounds were sampled by solid phase micro-extraction in the headspace of homogenated apple. Three varieties of apple (Fujion, Dalinette, Crimson Crisp) characterized by a trained sensory were used (Corollaro et al., 2013). The combination of both column sets, allowed the tentative identification, based on mass spectra and literature linear retention index, of about 90 volatile compounds. Each column set brought to the identification of about 60 compounds. The polar-apolar combination favored the identification of more alcohols while the apolar-polar combination was more efficient in separating terpenes, acids and aldehydes. The multivariate data analysis of the data showed a sample separation according the variety and characteristic volatile compounds within each variety were highlighted. The results are in agreement with sensory descriptive analysis, provided by a trined panel, of the same apples. For example Crimson Crisp, described by the panel as the most aromatic (with highest score for banana and pear descriptors) between the 3 cultivars, is characterized by higher amount of butyl and hexyl esters generally associated to fruity flavors.