A Headspace–SPME–MS Method for Monitoring Rapeseed Oil Autoxidation

Abstract  Headspace SPME–MS was used to analyze volatile compounds from rapeseed oil subjected to an accelerated storage test consisting of 0–12 days of storage at 60 °C. The SPME–MS data was compared with the data obtained by solid phase microextraction–gas chromatography/mass spectrometry (SPME–GC/MS). The SPME–GC/MS method allowed detection of 37 volatile compounds, of which 28 were identified. Predominant ones were hexanal, 2,4-heptadienal, 2-heptenal and 1-pentene-3-ol. Volatile compounds were not separated in SPME–MS—a single peak reflecting the total amount of volatiles was obtained. An increase in the abundance of characteristic ions in this peak could be used to detect of compounds characteristic for rapeseed oil autoxidation. These compounds (with their characteristic ions) were hexanal (m/z 56), 1-pentene-3-ol and 1-octene-3-ol (m/z 57), 2-pentenal and 2-heptenal (m/z 83 and 84), and 2,4-heptadienal (ions m/z 81 and 110). The SPME–MS peak area was correlated with peroxide value at 0.9779 and with Totox at 0.9841. Principal component analysis (PCA) of fatty acid volatile oxidation products from a model rapeseed oil indicated that SPME–MS was able to differentiate samples containing hexanal at a concentration of 0.2, 0.4, 0.6, 0.8 and 1.0 mg/L with proportional amounts of other compounds. Further, samples that were subjected to 0, 2, 4, 6, 8, 10 and 12 days of storage at 60 °C were differentiated using SPME–MS–PCA. PCA showed similarities in clustering of the data obtained by SPME–MS and sensory analysis.