Characterisation of Asturian cider apples on the basis of their aromatic profile by high-speed gas chromatography and solid-phase microextraction

Abstract

Headspace solid-phase microextraction (SPME) coupled to high-speed gas chromatography with FID detector (HSGC-FID) and with quadrupole mass spectrometric detector (GC–MS) was employed to study the volatile compounds in Asturian cider apples. The optimised conditions used for characterisation of cider apple were: sample equilibration at 25 °C for 12 h, followed by PDMS–DVB fibre exposure to the headspace above the sample for 5 min and finally thermal desorption of the adsorbed substances in the injector port for GC analysis. The use of high-speed gas chromatography allowed the separation of 27 compounds in less than 8 min, reducing the analysis time in 80% compared to conventional gas chromatography. A simple, rapid and reliable method to analyze volatile compounds in cider apples has been developed. The aromatic profile of 59 apple samples included in eight apple varieties was analysed. The different apples were obtained from two consecutive harvests (2005 and 2006). The apples volatile compounds together with chemometric techniques such as principal components analysis (PCA), Bayesian analysis and linear discriminant analysis (LDA), allowed us to differentiate apples on the basis of the sweet or sharp category to which the cider apple variety belongs. Volatile compounds such as ethyl heptanoate, E-farnesene, ethyl butyrate and hexyl caprylate are closely related to cider apple cultivars of the sweet category, while propyl butyrate and butyl acetate are related to the sharp class.