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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Agroecosystems Management Research » Research » Publications at this Location » Publication #329210
Title: Kinetics of forming aldehydes in frying oils and their distribution in French fries revealed by LC-MS-based chemometrics

Author
item WANG, LEI - University Of Minnesota
item CSALLANY, AGNES - University Of Minnesota
item Kerr, Brian
item SHURSON, GERALD - University Of Minnesota
item CHEN, CHI - University Of Minnesota

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2016
Publication Date: 4/29/2016
Citation: Wang, L., Csallany, A., Kerr, B.J., Shurson, G., Chen, C. 2016. Kinetics of forming aldehydes in frying oils and their distribution in French fries revealed by LC-MS-based chemometrics. Journal of Agricultural and Food Chemistry. 64:3881-3889.

Interpretive Summary: During deep frying of foods, thermal stress can extensively transform the chemical composition of frying oils, especially polyunsaturated fatty acids-enriched vegetable oils, and alter their nutritional value and toxicological profile. Among the many lipid oxidation products, aldehydes react with proteins and DNA and have been defined as major contributors to the adverse effects induced by the consumption of heated frying oils in animal and cell-based toxicity studies. At present, the kinetics of aldehyde production in frying oils, as well as the correlations between their levels in frying oils and fried foods, is generally undefined. The current study was designed to combine chemical derivatization, high-resolution LC-MS analysis, and multivariate chemometric analysis to characterize the kinetics of aldehyde formation in frying oils and their presence in French fries. The data from these experiments show that individual aldehydes and aldehyde clusters have distinctive kinetic profiles in frying oils, but a different distribution in French fries. In addition, correlations between individual aldehydes or aldehyde clusters with the duration of thermal stress were conducted, and suggests that these clusters may serve as the foundation for developing better analytical markers of lipid oxidation in frying oils and fried foods. This information provides scientists an improved understanding of corn oil peroxidation kinetics which will assist in the development of new analytical markers from which to evaluate the quality of frying oils and fried foods.

Technical Abstract: Aldehydes are major secondary lipid oxidation products (LOPs) from heating vegetable oils and deep frying. The routes and reactions that generate aldehydes have been extensively investigated, but the sequences and kinetics of their formation in oils are poorly defined. In this study, a platform combining 2-hydrazinoquinoline derivatization, high-resolution liquid chromatography-mass spectrometry (LC-MS) analysis, principal component analysis (PCA), and hierarchical cluster analysis (HCA), was adopted to characterize the kinetics of aldehydes produced during heating of frying oils. The PCA model of heated soybean oil (HSO) revealed a chemical profile that underwent a dramatic transition between 165°C to 185°C, and continued to change over time when held at 185°C. As major contributors to these changes in the model, aldehydes (I-XII) were grouped by HCA, based on their kinetics, into three clusters (A1, A2, and B) that corresponded to their fatty acid precursors (oleic acid, linoleic acid, and a-linolenic acid, respectively). Among these aldehydes and their clusters, 4-hydroxynonenal (4-HNE, V) and the A2:B ratio in HSO had strong linear correlations with the duration of thermal stress. A chemometric comparison of HSO, heated corn oil (HCO), and heated canola oil (HCAO) revealed different aldehyde profiles among the three frying oils, and further supported the associations between aldehyde profiles and fatty acid precursors. Furthermore, quantitative analysis of aldehydes showed that the concentrations of unsaturated aldehydes in French fry extracts were far below their concentrations in frying oils. The exceptions were the concentrations of pentanal, hexanal, acrolein, and the A2/B ratio in French fry extracts, which were of the same magnitude as their counterparts in the frying oils. In summary, individual aldehydes and aldehyde clusters have distinctive kinetic profiles in frying oils and a different distribution in French fries. The correlations between individual aldehydes or aldehyde clusters with the duration of thermal stress may serve as the foundation for developing better analytical markers of lipid oxidation in frying oils and fried foods.