Autoxidation oil

Deep fat frying, oil autoxidation, 623, 662 Deflagration, peroxides, 617 Degradation... 

Another potential area of application of FTIR spectroscopy is in the determination of the oxidative status or stability of an oil. Autoxidation is a major deteriorative reaction affecting edible fats and oils, and it is of major concern to processors and consumers from the standpoint of oil quality, as the oxidative breakdown products cause marked off flavours in an oil. A wide range of end products are associated with the autoxidative deterioration of fats and oils, the most important being hydroperoxides, alcohols, and aldehydes. Moisture, hydrocarbons, free fatty acids and esters, ketones, lactones, furans, and other minor products may also be produced, with the free fatty acids becoming more important in thermally stressed oils. In addition, there is significant cis to trans isomerisation and conjugation of double bonds in the hydroperoxides formed as an oil oxidises. 

Corrosion control by pigments relies on well-known principles of corrosion inhibition. Iron and steel exposed to air are quickly covered by an oxide film aqueous electrolytes tend to break down this film, and further oxidation of the metal surface ensues. The role of anodic corrosion inhibitors is to supplement or to aid in the repair of the surface oxide film. Basic pigments may form soaps, for example, with linseed oil autoxidation of these soaps may yield soluble inhibitors in the film. Some other pigments of limited solubility act directly as inhibitors. Active metal pigments supply electrons to the iron substrate and thus lower its potential and prevent metal dissolution. 

S. Mildner-Szkudlarz, H.H. Jelen, R. Zawirska-Wojtasiak, The use of electronic and human nose for monitoring rapeseed oil autoxidation. Eur. J. Lipid Sd. Technol. 110, 61-72 (2008) L.J. Dugan, Lipids, in Principles of Food Science, Parti, Food Chemistry, ed. by O.W. Fenema (Marcel Dekker Inc., New York, 1976), p. 183... 

Chemical Antioxidant Systems. The antioxidant activity of tea extracts and tea polyphenols have been determined using in vitro model systems which are based on hydroxyl-, peroxyl-, superoxide-, hydrogen peroxide-, and oxygen-induced oxidation reactions (109—113). The effectiveness of purified tea polyphenols and cmde tea extracts as antioxidants against the autoxidation of fats has been studied using the standard Rancimat system, an assay based on air oxidation of fats or oils. A direct correlation between the antioxidant index of a tea extract and the concentration of epigallocatechin gallate in the extract was found (107). 

Viscosity of drying oils also can be increased by passing air through the oil at relatively moderate temperatures, 140 to 150°C, to produce blown oils. Presumably, reactions similar to those involved in cross-linking cause autoxidative oligomeri2ation of the oil. 

Takahashi, A., Shibasaki-Kitakawa, N., and Yonemoto, T., Kinetic model for autoxidation of beta-carotene in organic solutions, J. Am. Oil Chem. ScL, 76, 897, 1999. 

Control skin formation as a result of autoxidation of alkyd or oil paint exposed to air. Representative classes of compounds are oximes and antioxidants. 

Are used to accelerate autoxidation and hardening of oxidisable coatings. Metal soaps, used as paint driers, can be made from a variety of carboxylic acids, including the commercially important naphthenic and 2-ethyl hexanoic acids, tall oil, fatty acids, neodecanoic and isononanoic acid. Cobalt is unquestionably the most active drier metal available. Metallic driers such as cobalt naphthenate or octoate and zinc salts can interact with UVAs, HALS, or AOs. 

The formation of peroxides and formaldehyde in the high-purity polyoxyethylene surfactants in toiletries has been shown to lead to contact dermatitis [31], Peroxides in hydrogenated castor oil can cause autoxidation of miconazole [32], Oxidative decomposition of the polyoxyethylene chains occurs at elevated temperature, leading to the formation of ethylene glycol, which may then be oxidized to formaldehyde. When polyethylene glycol and poloxamer were used to prepare solid dispersions of bendroflumethiazide, a potent, lipophilic diuretic drug, the drug reacted with the formaldehyde to produce hydroflumethiazide [33],... 

Autoxidation is responsible for the development of the rancidity that occurs when fats and oils spoil and for the spontaneous combustion of oily rags left open to the air. 

Oxidative rancidity is not necessarily a problem unless a polyunsaturated fat such as sunflower oil has been used. Where such a fat is used oxidative rancidity can occur and, as autoxidation occurs where the reaction becomes self-catalysing as oxygen free radicals react, some very unpleasant tastes can appear very quickly. In general, the effect of oxidation on biscuits at the end of their shelf life is that a cardboard taste starts to appear. 

In abroad sense, the model developed for the cobaloxime(II)-catalyzed reactions seems to be valid also for the autoxidation of the alkyl mercaptan to disulfides in the presence of cobalt(II) phthalocyanine tetra-sodium sulfonate in reverse micelles (142). It was assumed that the rate-determining electron transfer within the catalyst-substrate-dioxygen complex leads to the formation of the final products via the RS and O - radicals. The yield of the disulfide product was higher in water-oil microemulsions prepared from a cationic surfactant than in the presence of an anionic surfactant. This difference is probably due to the stabilization of the monomeric form of the catalyst in the former environment. 

This is used in manufacture of brake linings and is a polymer based on cashew nutshell liquid admixed with formaldehyde or furfuraldehyde and other ingredients. The polymerised resin mixture is cast into 8 cm thick slabs and then ground finely to produce the friction dust. Several fires have been experienced during bulk storage of the dust, attributed to autoxidation of the still partially unsaturated resin compound. Previously, linseed oil was used in place of the nutshell liquid, but fires were then more frequent. 

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