Multi-block analysis coupled with GC-FID and ATR-MIR for the evaluation of thermal degradation in vegetable oils.

The effect of heating in twenty-four different oil samples was evaluated via iodine value (IV), gas chromatography (GC) and mid-infrared (MIR) analyses. Common components and specific weights analysis (CCSWA) was applied to distribute the samples according to their most relevant characteristics, thereby revealing the influence of heating on composition. Instrumental analysis indicated a high amount of beneficial fatty acids, such as alpha-linolenic acid, in less exploited oils such as chia oil. This oil can present nutritional damage when subjected to high temperatures and is thus less recommended for frying. Conversely, oils containing high amounts of linoleic acid, such as almond and nut oils, as well as those containing equivalent amounts of alpha-linolenic and linoleic acids, such as golden flaxseed and flaxseed oils, displayed greater resistance to temperature. The 3008/cm band exhibited greater intensity in oils with a higher degree of unsaturation, such as chia and linseed oils, a phenomenon mainly influenced by the presence of linoleic and alpha-linolenic fatty acids. After heating, there was a decrease in the intensity of this band. The main parameter discriminating the tested oil samples based on CCSWA was the degree of unsaturation. Overall, the employed statistical method was effective in analyzing the data obtained via the applied techniques, revealing the influence of each assessed parameter.