Changes in the volatile profile, fatty acid composition and oxidative stability of flaxseed oil during heating at different temperatures

The deterioration of flaxseed oil (FSO) during heating greatly influences the quality of fried foods. FSOs heated at different temperatures (120 °C, 150 °C, 180 °C, and 210 °C) were investigated for volatile organic compound (VOC) and fatty acid compositions and physicochemical indices. In total, 84 VOCs were identified, including 20 aldehydes (37.43%–66.17%), 20 alcohols (31.19%–42.90%), 9 esters (0.28%–1.27%), 8 ketones (0.4%–1.58%), 19 alkanes (1.15%–19.96%), and 8 heterocyclics (0.68%–6.16%). Furthermore, 1-nonanal, 2,4-decadienal, hexanal, and trans,trans-2,4-heptadienal were identified as the characteristic aroma compounds to estimate the oxidation degree of heated FSO through the calculation of odor activity values. The polyunsaturated fatty acid content in FSO significantly (p < 0.05) decreased by 5.75 μg/g after heating at 210 °C. The physicochemical indices of FSO increased during heating with acid, peroxide, p-anisidine and thiobarbituric acid values ranging from 0.26 to 0.55 mg NaOH/g, 0.041–0.066 g/100 g, 0.12–0.88, and 0.025–0.088, respectively. Results of Pearson correlation analysis indicate that 2,4-decadienal and hexanal may be oxidation deterioration markers in FSO. This study provides a theoretical basis for evaluation of the suitability of FSO for household food preparation.