Quantification and monitoring the heat-induced formation of trans fatty acids in edible oils by Raman Spectroscopy

Trans fatty acids (TFAs), a type of unsaturated fatty acids, has been linked to increased risks of coronary heart disease and other health problems. Thus, efficient and reliable detection methods for TFAs are of great importance for both industrial applications and research purposes. In this study, a rapid and pretreatment-free quantification approach was developed for TFAs in 13 edible oils (including 2 soybean oils, 2 peanut oils, 2 rapeseed oils, blend oil, oleum camelliae, sunflower oil, rice oil, sesame oil, olive oil and corn oil) with Raman spectroscopy and chemometric methods. The commercial oils contained 0-0.397% (w/w) of trielaidin and each of the oils were further added with 0.1-5% of trielaidin, resulting in a total of 130 samples. Results show that the concentration of TFAs in various oils can be well-predicted based on the Raman spectral features in the region of 1640-1680 cm(-1) (characteristic to C=C stretching modes), yielding a residual predictive deviation (RPD) of 4.639. This approach exhibits high sensitivity in quantification, and TFAs added in different kinds of edible oils combined with their initial levels can be successfully quantified with good descriptive statistics (R-c = 0.9657, R-cv = 0.9598, R-p = 0.9634, RMSEC = 0.351, RMSECV = 0.391 and RMSEP = 0.302). Furthermore, in order to understand the heat-induced formation of TFAs during food preparation, the TFA concentrations of the oil heated under different temperatures was investigated based on the above predication model. The results indicate that the concentration of TFAs increased sharply when the oils were heated at 169-250 degrees C for 10 min.