Correlation of volatiles and fatty acids in thermally oxidized fatty acid model systems using statistical approaches

Distributions of volatiles and fatty acids from thermally oxidized free fatty acids (FFA) at 93°C for 200 min were analyzed and results were statistically compared using principal component analysis (PCA) and multiple factor analysis (MFA). Mixtures of FFA were composed of linoleic (57.54%), oleic (29.99%), linolenic (5.10%), palmitic (2.95%), stearic (0.26%), and arachadic (1.68%) acids. As thermal oxidation increased for 200 min, peak areas of total volatiles increased from 0.497 to 1.619 (1×10⁷ ion counts), the ratio of unsaturated to saturated fatty acids decreased from 21.65 to 17.65, 3 kinds of pattern changes of fatty acids, and 5 types of pattern changes of volatiles were observed. First principal component (PC1) and second principal component (PC2) expressed 77.34 and 10.02% of the data variability for the fatty acids during oxidation, respectively and 73.09 and 15.66% for the headspace volatiles, respectively. PCA and MFA analyses on fatty acids and volatiles showed that 2-heptenal had the highest correlation with the changes of linoleic acid compared to other volatiles under current oxidation conditions.