Effect Of Autoxidation Research Articles

Evaluation of oxidative stability of rice oil from brown rice flour under thermal oxidation and light irradiation.

Effects of autoxidation and light irradiation on the oxidative stability were evaluated in rice oil from two brown rice flours including 'Baromi2' and 'Samkwang'. 'Baromi2' is a newly developed variety for rice flour production while 'Samkwang' is a typical rice variety as a control. Degree of oxidation and volatile profiles were evaluated in rice oil stored at 60°C or under fluorescent light at 25°C. The oil yields of 'Baromi2' and 'Samkang' were 2.63 and 1.78%, respectively whereas rice oil from'Baromi2' had lower degree of unsaturation than 'Samkang'. Rice oil from 'Samkwang' possessed higher volatile compounds and more oxidized products during autoxidation whereas rice oil from 'Baromi2' had more oxidation products under light irradiation. Hexanal and 2-heptenal were major headspace volatile from heated rice oil while 2-heptenal and 1-octene-3-ol were main volatiles from light irradiated rice oil, which implies the involvement of singlet oxygen in rice oil during photooxidation.

Engine performance, exhaust emissions and combustion characteristics of a CI engine fuelled with croton megalocarpus methyl ester with antioxidant

The use of biodiesel as a substitute for petroleum-based diesel has become of great interest for the reasons of combating the destruction of the environment, the price of petroleum-based diesel and dependency on foreign energy sources. But for practical feasibility of biodiesel, antioxidants are added to increase the oxidation stability during long term storage. It is quite possible that these additives may affect the clean burning characteristics of biodiesel. This study investigated the experimental effects of antioxidants on the oxidation stability, engine performance, exhaust emissions and combustion characteristics of a four cylinder turbocharged direct injection (TDI) diesel engine fuelled with biodiesel from croton megalocarpus oil. The three synthetic antioxidants evaluated its effectiveness on oxidation stability of croton oil methyl ester (COME) were 1, 2, 3 tri-hydroxy benzene (Pyrogallol, PY), 3, 4, 5-tri hydroxy benzoic acid (Propyl Gallate, PG) and 2-tert butyl-4-methoxy phenol (Butylated Hydroxyanisole, BHA). The fuel sample tested in TDI diesel engine include pure croton biodiesel (B100), croton biodiesel dosed with 1000ppm of an effective antioxidant (B100+PY1000), B20 (20% croton biodiesel and 80% mineral diesel) and diesel fuel which was used as base fuel. The result showed that the effectiveness of the antioxidants was in the order of PY>PG>BHA. The brake specific fuel consumption (BSFC) of biodiesel fuel with antioxidants decreased more than that of biodiesel fuel without antioxidants, but both were higher than that of diesel. Antioxidants had few effects on the exhaust emissions of a diesel engine running on biodiesel. Combustion characteristics in diesel engine were not influenced by the addition of antioxidants in biodiesel fuel. This study recommends PY and PG to be used for safeguarding biodiesel fuel from the effects of autoxidation during storage. Overall, the biodiesel derived from croton megalocarpus oil can be utilized as partial substitute for mineral diesel.

Effect of antioxidants on the oxidative stability and combustion characteristics of biodiesel fuels in an indirect-injection (IDI) diesel engine

Biodiesel fuels that consist of saturated and unsaturated long-chain fatty acid alkyl esters are an alternative diesel fuel produced from vegetable oils or animal fats. However, autoxidation of biodiesel fuels during storage is easily caused by air, reducing fuel quality by adversely affecting its properties such as kinematic viscosity and acid value. One approach to improve the resistance of biodiesel fuels to autoxidation is to mix them with antioxidants. This study investigated the effectiveness of five such antioxidants in mixtures with biodiesel fuels produced by three biodiesel manufacturers: butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ), propyl gallate (PrG) and α-tocopherol. An engine test was also performed to investigate the combustion characteristics of biodiesel fuel with antioxidants in an indirect-injection (IDI) diesel engine. Oxidation stability was determined using Rancimat equipment. The results showed that TBHQ, BHA, and BHT were the most effective and α-tocopherol was the least effective in increasing the oxidation stability of biodiesel. The combustion characteristics and exhaust emissions in diesel engine were not influenced by the addition of antioxidants in biodiesel fuel. This study recommends TBHQ and PrG to be used for safeguarding biodiesel fuel from the effects of autoxidation during storage.

Effect of antioxidants on the oxidative stability of methyl soyate (biodiesel)

Biodiesel, an alternative diesel fuel derived from transesterification of vegetable oils or animal fats, is composed of saturated and unsaturated long-chain fatty acid alkyl esters. When exposed to air during storage, autoxidation of biodiesel can cause degradation of fuel quality by adversely affecting properties such as kinematic viscosity, acid value and peroxide value. One approach for increasing resistance of fatty derivatives against autoxidation is to treat them with oxidation inhibitors (antioxidants). This study examines the effectiveness of five such antioxidants, tert-butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PrG) and α-Tocopherol in mixtures with soybean oil fatty acid methyl esters (SME). Antioxidant activity in terms of increasing oxidation onset temperature (OT) was determined by non-isothermal pressurized-differential scanning calorimetry (P-DSC). Analyses were conducted in static (zero gas flow) and dynamic (positive gas flow) mode under 2000 kPa (290 psig) pressure and 5 °C/min heating scan rate. Results showed that PrG, BHT and BHA were most effective and α-Tocopherol least effective in increasing OT. Increasing antioxidant loading (concentration) showed sharp increases in activity for loadings up to 1000 ppm followed by smaller increases in activity at higher loadings. Phase equilibrium studies were also conducted to test physical compatibility of antioxidants in SME-No. 2 diesel fuel (D2) blends. Overall, this study recommends BHA or TBHQ (loadings up to 3000 ppm) for safeguarding biodiesel from effects of autoxidation during storage. BHT is also suitable at relatively low loadings (210 ppm after blending). PrG showed some compatibility problems and may not be readily soluble in blends with larger SME ratios. Although α-Tocopherol showed very good compatibility in blends, it was significantly less effective than the synthetic antioxidants screened in this work.

Effect of Autoxidation of Hydrogenated Castor Oil Containing 60 Oxyethylene Groups on Degradation of Miconazole.

Effect of Autoxidation of Hydrogenated Castor Oil Containing 60 Oxyethylene Groups on Degradation of Miconazole.

The effect of autoxidation on the methanogenic toxicity and anaerobic biodegradability of pyrogallol

In a previous study, catechin (a condensed tannim monomer) was polymerized by autoxidation treatments. The resulting oligomeric tannins were responsible for the methanogenic toxicity observed in the autoxidized catechin solutions (Field, J. A., Kortekaas, S. & Lettinga, G. (1989). The tannin theory of methanogenic toxicity. Biol. Wastes 29(4) 241-62). In this study the autoxidation of pyrogallol (a hydrolyzable tanning monomer) did not cause extensive polymerization. Initially, some polymerization occurred, producing toxic intermediates that were later destroyed by a destructive type of oxidation caused by prolonged autoxidation treatments. The first intermediate formed, purpurogallin (a dimer), caused a high level of toxicity to both the methanogenic activity and to the anaerobic degradation of pyrogallol. Since purpurogallin is a highly toxic autoxidation product that lacks tannic features, the changes in methanogenic toxicity induced by the autoxidation of pyrogallol cannot be estimated by changes in the oligomeric tannin concentration. Regardless of the reactions that take place during the autoxidation of tannin monomeric derivatives, the initial reactions can potentially lead to colored products of increased methanogenic toxicity. These are later detoxified by prolonged autoxidation, either by polymerization to high MW compounds (with condensed tannin model compounds), or by destruction of the initially toxic intermediates to low MW compounds (with hydrolyzable tannin model compounds).

Effect of Autoxidation on the Nutritive Value of Acidulated Soybean Soapstock in Chicks

ACIDULATED soybean-oil soapstock (ASS) has recently become the main fat supplement for poultry feeds in Israel. This by-product of the edible oil industry is obtained from the alkali-neutralization of the crude oil in the form of raw soapstock (a mixture of soaps, neutral oil, water, sterols, pigments and other minor constituents). This rather unstable product is converted to acidulated soapstock by treatment with an excess of hot aqueous sulfuric acid.Most of the “impurities” which are removed from the crude oil by alkali-refining accumulate in the acidulated soapstock. Compared to crude soybean oil (CSO), ASS contains high levels of free fatty acid (over 50%), unsaponifiable matter and oxy-fatty acids (Bornstein and Lipstein, 1963), and is also rich in carotenoids (Budowski et al., 1964).Previous work of this labortory (Bornstein and Lipstein, 1961, 1963), as well as that of Sibbald et al. (1962), has shown that ASS is comparable to tallow…

Effects of Autoxidation on Antiacrodynic Potency of Fats and Linoleic Esters

Effects of Autoxidation on Antiacrodynic Potency of Fats and Linoleic Esters