Comparative 1H NMR-Based Chemometric Evaluations of the Time-Dependent Generation of Aldehydic Lipid Oxidation Products in Culinary Oils Exposed to Laboratory-Simulated Shallow Frying Episodes: Differential Patterns Observed for Omega-3 Fatty Acid-Containing Soybean Oils.

Angela I Wann,Benita C Percival,Miles Gibson,Katy Woodason,Siâny Vincent,Martin Grootveld

doi:10.3390/foods10102481

Angela I Wann, Benita C Percival + Show 4 more

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https://doi.org/10.3390/foods10102481

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Abstract

Soybean oil is the second most exported oil from the United States and South America, and is widely marketed as a cooking oil product containing numerous health benefits for human consumers. However, culinary oils with high polyunsaturated fatty acid (PUFA) contents, are known to produce high quantities of lipid oxidation products (LOPs), including toxic aldehydes upon exposure to high-temperature frying episodes. Previous studies have demonstrated causal links between aldehyde ingestion and inhalation with deleterious health perturbations, including mutagenic and carcinogenic effects, along with cardiovascular and teratogenic actions. In this study, aldehydic LOPs were detected and quantified in commercially available samples of soybean, avocado, corn and extra-virgin olive oil products before and after their exposure to laboratory-simulated laboratory frying episodes (LSSFEs) using high-resolution 1H nuclear magnetic resonance (NMR) analysis. Results acquired demonstrated that PUFA-rich soybean and corn oils gave rise to the highest concentrations of oil aldehydes from the thermo-oxidation of unsaturated fatty acids, whereas monounsaturated fatty acid (MUFA)-laden avocado and olive oils were much more resistant to this peroxidation process, as expected. Multivariate chemometrics analyses provided evidence that an orthogonal component pattern of aldehydic LOPs featuring low-molecular-mass n-alkanals such as propanal, and 4-oxo-alkanals, arises from thermo-oxidation of the ω-3 fatty acid (FA) linolenic acid (present in soybean oils at levels of ca. 7% (w/w)), was able to at least partially distinguish this oil from corresponding samples of thermally-stressed corn oil. Despite having a similar total PUFA level, corn oil has only a negligible ω-3 FA content, and therefore generated significantly lower levels of these two aldehyde classes. In view of the adverse health effects associated with dietary LOP ingestion, alternative methodologies for the incorporation of soybean oils within high-temperature frying practices are proposed.

Highlights

Culinary frying oils which contain high contents of unsaturated fatty acids (UFAs), polyunsaturated fatty acids (PUFAs), oxidatively deteriorate when exposed to high-temperature frying practices at ca. 180 ◦ C, most especially when reused for this purpose [1]
For the investigation of distinctive patterns of aldehydic lipid oxidation products (LOPs) thermo-oxidatively generated in differing culinary oils during their exposure to laboratorysimulated shallow frying episodes (LSSFEs), including that arising from the distinctively higher ω-3 FA content of soybean oils, from those mainly derived from linoleoylglycerol and/or oleoylglycerol peroxidation in linolenoylglycerol-depelete oils, we employed a combination of both UV and MV statistical analysis techniques
Evidence presented in the current study suggests that the employment of genetically engineered, high oleoylglycerol content soybean oils would be more suitable for high-temperature culinary frying or cooking purposes, in view of substantial reductions in PUFA content and those of toxic aldehydes formed during such frying episodes

Summary

Introduction

Culinary frying oils which contain high contents of unsaturated fatty acids (UFAs), polyunsaturated fatty acids (PUFAs), oxidatively deteriorate when exposed to high-temperature frying practices at ca. 180 ◦ C, most especially when reused for this purpose [1]. The production of primary LOPs, lipid hydroperoxides, including hydroperoxymonoenes (HPMs) and conjugated hydroperoxydienes (CHPDs), is critically dependent on the fatty acid (FA) contents of culinary oils employed for frying practices, the former being derived from oleoylglycerols, and the latter from linoleoyl- and more highly unsaturated linolenoylglycerols [1,3,6]. Since these primary products are chemically unstable at high frying temperatures, they fragment to a wide range of secondary LOPs, including alcohols, ketones, oxoacids, alkenes and alkanes; aldehydes, both saturated and unsaturated, represent the most important of these secondary LOPs in view of their high levels of generation and adverse toxicological properties potentially exertable in humans consuming fried foods, or those inhaling such toxins during frying practices [1,5]. Further LOPs include a series of toxic epoxy-fatty acids [1,2]

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