Synthesis and analysis of tocopheryl quinone and tocopherol esters with fatty acids in heated sunflower oil

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The paper describes laboratory deodorization of rapeseed oil (Ro), model sunflower (SoM), and model rapeseed (RoM) oils, its effect on the tocopherol content and the kinetics of tocopherol degradation. We now present a novel approach to analysis of alpha‐tocopherol degradation product as well as kinetic study esters of alpha‐tocopherol with fatty acids and alpha‐tocopheryl quinones. Alpha‐tocopherol esters were found to be the principal products of tocopherols degradation in high temperature experiment. A laboratory deodorization, lasting 2 h caused formation of 70–128 mg/kg of alpha‐tocopherol esters in model oils and 25 mg/kg of alpha‐tocopherol esters in rapeseed oil without modification. The commercially available sunflower and rapeseed oils contained 3–12 mg/kg of alpha‐tocopherol esters. The alpha‐tocopherol esters are formed at higher rate than alpha‐tocopheryl quinone, which was unstable at high deodorization temperature. Tocopherols took no part in non‐radical thermal reactions, taking place in second high‐temperature experiments with oxygen‐free atmosphere. We proved by DART TOF‐MS the formation of polymeric fatty acids via Diels–Alder reaction taking place in heated oils. Practical applications: Although an extensive research have been conducted in the area of high‐temperature degradation of tocopherols, this is the first report on formation of fatty acids esters of tocopherols during oil deodorization. The proof of their presence in deodorized oils, deodorization condensates, deep‐fried foods, and oils constitutes a breakthrough. We ingested them as yet unknowingly. Their degradation is not nearly as fast as that of tocopherol itself or its oxidation products. In the course of their hydrolysis in stomach tocopheryls of fatty acids could thus become the source of unoxidized tocopoherols. We found out that during laboratory deodorization of vegetable oils were formed esters of tocopherols with fatty acids. During heating of oils are free fatty acids the acid catalyst of esterification.

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of deodorization temperature on formation of tocopherol esters and fatty acids polymers in vegetable oil

Kreps

Kyselka

Burčová

et al. 2016

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“…Figure shows, for both deep‐ (Figure 2A) and pan‐frying (Figure 2B), the amount of total tocochromanols in the frying oil (dots joined by a dashed line) and in the oil extracted from fried potatoes (dots only). According to Kreps, Burcovà, & Schmidt, [ 18 ] during frying, there is a progressive decrease of tocochromanols with the heating time. Among tocochromanols, α ‐TOC has the highest degradation rate being the less stable towards oxidation, followed, in increasing order of stability, by β‐TOC, γ‐TOC, and PC‐8 (data not shown).…”

Section: Resultsmentioning

confidence: 99%

“…[ 15 ] Among these, TOC are considered the best natural chain‐breaking antioxidants [ 16 ] and their key role on the protection against oil deterioration during frying is well established. [ 17,18 ]…”

Section: Introductionmentioning

confidence: 99%

Formation of Alkylbenzenes and Tocochromanols Degradation in Sunflower Oil and in Fried Potatoes during Deep‐Frying and Pan‐Frying

Padovan

Moret

Bortolomeazzi

et al. 2020

Formation of toxic alkylbenzenes, total polar compounds (%TPC) and degradation of tocochromanol are monitored. Analyses of the oil extracted from fried potatoes confirm the trend observed in the frying oil. The fresh oil has a TPC content of 3%, which increases with the frying time, exceeding the acceptable value (25%) after about 25 h for deep-frying and 1.5 h for pan-frying. During deep-frying, total tocochromanol decreases to about half (25 mg per 100 g) of the initial value, pan-frying shows faster, degradation (complete after 1.5 h). Toluene concentration increases with the frying time reaching a maximum, and afterwards gradually decreases. Except for butylbenzene during pan-frying, pentylbenzene and butylbenzene concentration, increase with the frying time, but remain much lower than toluene. Practical Applications: This is the first systematic work comparing alkylbenzenes evolution under different frying conditions. Different from previous works, frying experiments are carried out following the indication of many European countries that recommend using temperature lower than 180°C. The amount of alkylbenzenes assumed through a standard portion of fried potatoes (200 g) is assessed, which is relevant for evaluating dietary exposure to these contaminants.

Degradation of fatty acids and tocopherols to form tocopheryl quinone as risk factor during microwave heating, pan‐frying and deep‐fat frying

Kreps

Burčová

Schmidt

2016

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We investigated degradation of tocopherols to form tocopheryl quinones (TQ) and cytotoxic γ‐tocopheryl quinone in oils and French fries during microwave heating, pan‐frying and deep‐fat frying. We proved that the microwave oven caused rapid increase of oil temperature, with the consequence of two to three times greater degradation of fatty acids and tocopherols than pan‐frying and deep‐fat frying. Pan‐frying with sunflower oil caused three‐time greater formation of fatty acids polymers, compare with rapeseed oil. The gentlest one was deep‐fat frying, which caused two times slower formation of fatty acid hydroperoxides and tocopheryl quinones in 900 g of oil. We found that not only the quantity but also the type of oil had critical effect on the formation of cytotoxic γ‐tocopheryl quinone. During 50 min of pan‐frying in rapeseed oil, 22 mg/kg of γ‐tocopheryl quinones was formed, of which 5–7 mg/kg penetrated into the homemade French fries. While the deep‐fat frying technique generated only 6 mg/kg of γ‐tocopheryl quinones in rapeseed oil. The rapid microwave heating caused formation of 8 mg/kg of γ‐tocopheryl quinones within 10 min. The emergence of γ‐tocopheryl quinones during culinary preparation of food has not yet been explored. Practical applications: Although an extensive research have been conducted in the area of microwave heating of foods, this is the first report about formation of cytotoxic γ‐tocopheryl quinone in microwave‐heated rapeseed oil. Formation of this reactive compound was also confirmed during frying process. The most γ‐tocopheryl quinone was formed during pan‐frying and subsequently entered into fried food. It was observed that the amount of oil used for frying has a major impact on slowing formation of cytotoxic γ‐tocopheryl quinone and other tocopherols and fatty acids degradation product. Formation of health‐promoting α‐tocopheryl quinone and cytotoxic γ‐tocopheryl quinone during pan‐frying.