Volatile Oxidation Compounds and Stability of Safflower, Sesame and Canola Cold-Pressed Oils as Affected by Thermal and Microwave Treatments

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The goal of this study was to investigate the effect of heating and microwave treatment on the levels of volatile oxidation products and the stability of safflower (Carthamus tinctorius L.), sesame (Sesamum indicum) and canola (Brassica napus L.) cold-pressed oils. Cold-pressed oils were subjected to conventional heating (oven test) using air-forced oven at 60°C and microwave heating for 2 and 4 min. The changes in conjugated diene (CD) and conjugated triene (CT) values were monitored during treatments. As expected, heating generates an increase in CD and CT values. The volatile compounds in treated oils were determined using solid phase micro-extraction-gas chromatography/mass spectrometry (SPME-GC/MS). The obtained GC/MS data were used to characterize volatile compounds of cold-pressed oils during heating and microeave treatments. Under oven conditions, 2-heptenal and 2,4-heptadienal isomers were identified as major components in canola oil, while hexanal and 2-heptenal were found in high levels in safflower and sesame oils. Among volatiles, p-cymene was the dominant compound found in microwave-treated canola oil. In addition, hexanal and 2-hexenal were found at high amounts upon microwave treatment especially after 4 min of application.