Mechanisms and Factors for Edible Oil Oxidation

Abstract

Edible oil is oxidized during processing and storage via autoxidation and photosensitized oxidation, in which triplet oxygen ( 3 O 2 ) and singlet oxygen ( 1 O 2 ) react with the oil, respectively. Autoxidation of oils requires radical forms of acylglycerols, whereas photosensitized oxidation does not require lipid radicals since 1 O 2 reacts directly with double bonds. Lipid hydroperoxides formed by 3 O 2 are conjugated dienes, whereas 1 O 2 produces both conjugated and nonconjugated dienes. The hydroperoxides are decomposed to produce off-flavor compounds and the oil quality decreases. Autoxidation of oil is accelerated by the presence of free fatty acids, mono-and diacylglycerols, metals such as iron, and thermally oxidized compounds. Chlorophylls and phenolic compounds decrease the autoxidation of oil in the dark, and carotenoids, tocopherols, and phospholipids demonstrate both antioxidant and prooxidant activity depending on the oil system. In photosensitized oxidation chlorophyll acts as a photosensitizer for the formation of 1 O 2 ; however, carotenoids and tocopherols decrease the oxidation through 1 O 2 quenching. Temperature, light, oxygen concentration, oil processing, and fatty acid composition also affect the oxidative stability of edible oil.

Effect of pretreatment on the proximate composition, physicochemical characteristics and stability of <em>Moringa peregrina</em> oil

“…With reference to the peroxide value, most studies (Anjum et al, 2006;Vujasinovic et al, 2012) reported a noticeable increase in the peroxide value with increasing roasting temperature and time whereas a few others (Abou-Gharbia et al, 2000) observed only a marginal decrease compared to unroasted samples. Generally, peroxide value does not correspond to the absolute state of oxidation of oil because hydroperoxides become unstable upon heating and decompose to secondary products (Choe and Min, 2006). Furthermore, roasting decreased the acid value (AV) from 0.68 mg KOH/g for the raw sample to 0.25 mg KOH/g for the roasted one (p < 0.05).…”

Effect of added herb extracts on oxidative stability of ghee (butter oil) during accelerated oxidation condition

“…Ghee undergoes oxidative degradation during storage, resulting in alteration of major quality parameters such as colour, flavour, aroma and nutritive value affecting suitability for consumption. The primary autoxidation products are hydroperoxides, which have no taste and flavour, while their degradation products, called secondary oxidation products have detectable taste and flavor (Choe and Min 2006).…”

Photoinduced Electron Transfer Reaction of 2-Thiobarbituric Acid and Methylene Blue: Mechanism and Kinetics

“…This singlet oxygen is a highly reactive species which gives the photo oxygenation reaction. Methylene blue is reportedly efficient sensitizers for the conversion of triplet oxygen to singlet oxygen in the presence of light [15][16][17][18][19] . The first-order kinetic constant was calculated for the exposed solutions of the different concentration of the substrate [2TBA] and the sensitizer MB in the aerobic as well as in the anaerobic condition.…”