Monitoring the oxidation of almond oils by HS-SPME–GC–MS and ATR-FTIR: Application of volatile compounds determination to cultivar authenticity

In this study, the oxidative process of Spanish and American almond oils was monitored by using headspace solid-phase microextraction/gas chromatography–mass spectrometry (HS-SPME/GC–MS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Oxidative stability of samples was evaluated after thermal treatment at 100 °C for 1, 3, 5, 7, 10, 15 and 20 days, in order to accelerate the lipid oxidation process. Variations observed in bands of infrared spectra were used to monitor the progress of the oxidation process of almond oils. HS-SPME–GC–MS was used for isolation and determination of volatile compounds in oxidised almond oils. The following aldehydes were identified in all samples: hexanal, (E)-2-heptenal, (E)-2-octenal, nonanal, (E)-2-nonenal, (E,E)-2,4-nonadienal and (E,E)-2,4-decadienal. Determination of volatile compounds resulting from lipid oxidation from three different almond cultivars (Spanish Guara and Marcona and Butte from USA) was performed to obtain a set of parameters for discrimination between Spanish and American cultivars. Successful discrimination was obtained in samples kept under thermal treatment for 7 days, by using HS-SPME/GC–MS combined with multivariate stepwise linear discriminant analysis (LDA).