Analysis of Volatile Compounds Changes during the Oxidation of Pressed Rapeseed Oil

Abstract

Volatile flavor components of first-grade pressed rapeseed oil (S1) and fourth-grade pressed rapeseed oil (S2) subjected to accelerated oxidation test at 60 ℃ were profiled by means of headspace solid-phase microextraction with gas chromatography-mass spectrometry (HS-SPME-GC-MS) coupled with electronic nose (E-nose) technology, followed by correlation analysis with quality indicators. The results showed that the acid value of S1 and S2 was related to acid compounds. The content of aldehyde compounds had an important correlation with the degree of oxidation deterioration. The peroxide value of S1 was generally higher than that of S2. After 20 d of accelerated oxidation, S1 had a higher anisidine value than S2. S1 had a high oxidation rate in the early stage of oxidation, and S2 had a high oxidation rate in the later stage of oxidation. It showed that the deterioration degree of S1 was higher than that of S2. The main volatile components of rapeseed oil during accelerated oxidation were mainly aldehydes. The characteristic flavor components of S1 accelerated oxidation for 20 days were nonanal, decanal, 2,4-decadienal and 2-decanone. The characteristic flavor components of S2 accelerated oxidation for 20 days were (E)-2-decenal. The E-nose radar chart could distinguish unoxidized oil and oxidized oil, as well as the difference in flavor components in the early and late stages of oxidation. The content of (E)-2-decenal, (E)-2-nonenal, octanal and 2-undecenal were related to the peroxide value, anisidine value and total oxidation value of S1. The content of nonanal, (E,E)-2-4 decenal, (E)-2-decenal, (E)-2-nonenal, decanal, octyl aldehyde and heptanal were related to the peroxide value, anisidine value and total oxidation value of S2. Volatile components can be used as indicators to monitor the oxidation degree of rapeseed oil during storage.