Effects of photosensitisation and autoxidation on the changes of volatile compounds and headspace oxygen in elaidic trans fatty acid and oleic cis fatty acid

Headspace volatiles and oxygen in elaidic or oleic acids under methylene blue photosensitisation at 60 °C for 60 h were analysed by solid-phase microextraction (SPME)-gas chromatography (GC) with a mass selective detector (MS) and GC with a thermal conductivity detector (TCD), respectively. Headspace oxygen was significantly depleted in photosensitised samples compared to those in the dark (p < 0.05). Oleic acid absorbed more oxygen than elaidic acid for 60 h photosensitisation at 60 °C. Total volatiles from elaidic or oleic acids under photosensitisation increased significantly than those from samples in the dark for 60 h, respectively (p < 0.05). The increasing rates of oxidised volatiles in elaidic acid under photosensitisation were higher than those in oleic acid for 60 h. Peak areas of t-2-undecenal, 1-octanol and 1-heptanol were greatly increased in both elaidic and oleic acids under photosensitisation. Photosensitisation accelerated formation of volatiles in elaidic acid more than in oleic acid while oleic acid absorbed more oxygen than elaidic acid at 60 °C for 60 h.