Oil Quality Control of Culinary Oils Subjected to Deep-Fat Frying Based on NMR and EPR Spectroscopy

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Oil Quality Control of Culinary Oils Subjected to Deep-Fat Frying Based on NMR and EPR Spectroscopy David Castejón 1 & Antonio Herrera 2 & Ángeles Heras 3 & Isabel Cambero 4 & Inmaculada Mateos-Aparicio 5

Received: 14 July 2016 / Accepted: 20 December 2016 # Springer Science+Business Media New York 2017

Abstract The culinary oils, sunflower and olive, and the oil from the cultivated cardoon (Cynara cardunculus L.) were submitted to deep-fat frying during 36 h. The heterospectroscopy analysis by nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) allowed to control oil quality through the monitor of (1) the percentage of fatty acid types (increase of saturated and decrease of polyunsaturated fatty acids), (2) the new compounds formed (aldehydes and peroxides), and (3) the oil oxidative stability during the deep-fat frying. The aldehyde content was much higher in sunflower and cynara oils than in olive; however, the epoxides increased more in this oil. Oxidative stability measured by EPR was correlated (p < 0.05) with the aldehyde formation measured by NMR. The multivariate analysis of the NMR data allowed Electronic supplementary material The online version of this article (doi:10.1007/s12161-016-0778-x) contains supplementary material, which is available to authorized users. * Inmaculada Mateos-Aparicio [email protected] 1

Centro de Asistencia a la Investigación de Resonancia Magnética Nuclear y de Espín Electrónico, Universidad Complutense de Madrid, 28040 Madrid, Spain

2

Departamento de Química Orgánica, Facultad de Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain

3

Instituto de Estudios Biofuncionales, Departamento de Química-Física II, Universidad Complutense de Madrid, Paseo de Juan XXIII, 1, 28040 Madrid, Spain

4

Departamento de Nutrición, Bromatología y Tecnología de los Alimentos, Facultad de Veterinaria, Universidad Complutense de Madrid, 28040 Madrid, Spain

5

Departamento de Nutrición y Bromatología II, Facultad de Farmacia, Universidad Complutense de Madrid, 28040 Madrid, Spain

classifying the oils depending on (a) the oxidation degree (PC1) and (b) the fatty acid composition (PC2). Moreover, the favorable behavior of cynara oil suggests the potential use as frying edible oil. Keywords Edible oils . Cardoon . Deep-fat frying . NMR . EPR

Introduction Deep-fat frying is one of the oldest and popular food preparations because fried foods have desirable organoleptic properties such as flavor or color. Frying consists of immersing food in hot oil at a high temperature (160 to 190 °C). The frying oil suffers common chemical reactions such as hydrolysis, oxidation, and polymerization (Choe and Min 2007). Lipid oxidation is the most important cause of oil and fat deterioration, reducing shelf-life and nutritional value, which can lead to rejection by consumers and losses for the target industries. During lipid oxidation, hydroperoxides are formed as primary products that are easily decomposed to secondary products such as aldehydes, ketones, alcohols, and acids (