Direct FTIR analysis of isolated trans fatty acids in edible oils using disposable polyethylene film

New research development on trans fatty acids in food: Biological effects, analytical methods, formation mechanism, and mitigating measures

The trans fatty acids (TFAs) in food are mainly generated from the ruminant animals (meat and milk) and processed oil or oil products. Excessive intake of TFAs (>1% of total energy intake) caused more than 500,000 deaths from coronary heart disease and increased heart disease risk by 21% and mortality by 28% around the world annually, which will be eliminated in industrially-produced trans fat from the global food supply by 2023. Herein, we aim to provide a comprehensive overview of the biological effects, analytical methods, formation and mitigation measures of TFAs in food. Especially, the research progress on the rapid, easy-to-use, and newly validated analytical methods, new formation mechanism, kinetics, possible mitigation mechanism, and new or improved mitigation measures are highlighted. We also offer perspectives on the challenges, opportunities, and new directions for future development, which will contribute to the advances in TFAs research.

Evaluation of trans fatty acids, carbonyl compounds and bioactive minor components in commercial linseed oils

Trans fatty acids (TFAs), associated with the risks of coronary heart disease and diabetes, are formed by isomerization of unsaturated fatty acids during refining of linseed oils. In this study, TFAs and the chemical characteristics (acid value, peroxide value, carbonyl compounds, bioactive minor components and fatty acids) in 32 commercial linseed oils were investigated, and the correlation among them were further analyzed. Results showed that C18:3 TFAs were predominant TFAs in linseed oils and about 9% of the samples had TFA contents above 2 g/100 g fat, as well as the average level of TFA in the refined samples was higher than that in the unrefined oils. The correlation analyses suggested C18:3 TFAs exhibited significant negative correlations with acid value, levels of acetone, trans-2-nonenal, campesterol and α-linolenic acid. These results provided a comprehensive insight of TFAs in linseed oil and had important implications for consumers and linseed oil industry.

Structure determination of conjugated linoleic and linolenic acids

Conjugated linoleic and linolenic acids (CLA and CLnA) can be found in dairy, ruminant meat and oilseeds, these types of unsaturated fatty acids consist of various positional and geometrical isomers, and have demonstrated health-promoting potential for human beings. Extensive reviews have reported the physiological effects of CLA, CLnA, while little is known regarding their isomer-specific effects. However, the isomers are difficult to identify, owing to (i) the similar retention time in common chromatographic methods; and (ii) the isomers are highly sensitive to high temperature, pH changes, and oxidation. The uncertainties in molecular structure have hindered investigations on the physiological effects of CLA and CLnA. Therefore, this review presents a summary of the currently available technologies for the structural determination of CLA and CLnA, including the presence confirmation, double bond position determination, and the potential stereo-isomer determination. Special focus has been projected to the novel techniques for structure determination of CLA and CLnA. Some possible future directions are also proposed.

Rapid Determination of Acid Value of Edible Oils via FTIR Spectroscopy Using Infrared Quartz Cuvette

A Fourier transform infrared (FTIR) spectroscopy with infrared quartz cuvette (IQC) as spectral accessory method was developed to determine acid value (AV) of edible oils. The absorption peak at 5680 cm^-1/5487 cm^-1 ascribed to the C-H stretching band was a substitute for the peak of an internal standard. Partial least square (PLS) regression was used for AV calibration, and samples were validated by titrated method. Results showed dilution calibration was feasible for randomly dilution among 6-13:1 (CCl₄: oils, v/v). PLS calibration was optimal by a spectral wavenumber (3603 cm^-1-3250 cm^-1) as the first derivative treatment. Correlation coefficient and root mean square error of calibration were 0.9967 and 0.135, respectively. Calibrated validation, blind sample validation and precision analysis presented a good correlation between IQC-FTIR and titrated methods. Based on the dilution calibration, randomly diluted oil samples can be employed by IQC-FTIR.