Antioxidants In Vegetable Oils Research Articles

The use of antioxidants in vegetable oils – A review

The shelf life of vegetable oils in food uses and their applicability in industrial situations is greatly dependent on their oxidative stabilities. Methods of improving oxidative stability values currently available include genetic modifications, compositional changes via chemical means, as well as the inhibition of oxidation by means of substances known as antioxidants. This paper reviews the properties of vegetable oils which predispose them to auto oxidation reactions, explores the nature and mechanisms of the operation of antioxidants in brief, and finally summarizes current research efforts geared towards identifying and evaluating the effectiveness and commercial promise of less toxic new antioxidants derived as natural extracts from various plant species.

The effect of nitrogen fertilization on tocopherols in rapeseed genotypes

Tocopherols (α-, β-, γ- and δ-tocopherol) are naturally occuring antioxidants in vegetable oils. In rapeseed oil, α- and γ-tocopherols are the predominant isomers, while δ-tocopherol contributes much lower amounts to the total tocopherol content. Enhanced tocopherol content in seeds appears favourable, and breeding for tocopherol content has become an increasingly important objective in winter oilseed rape. The main objectives of this research were to quantify the amount of tocopherols in a number of rapeseed varieties and to investigate the effect of nitrogen fertilization on tocopherol concentration in the seed. The field trials were carried out in 2004–2005 and 2005–2006 at Dardanos, Canakkale on the Turkish West Coast (10 km south of the city centre) with 13 varieties, three replications and three nitrogen levels (N0: 0 kg/ha, N1: 130 kg/ha and N2: 260 kg/ha). The trial used a randomized complete block design with 6 m2 plots. Tocopherol analysis was done using an HPLC system. Significant differences were found among the varieties and between the nitrogen levels. The average total tocopherol concentration was 118.7 mg kg−1 for N1, 134.1 mg kg−1 for N2 and 133.6 mg kg−1 for N3 fertilization level. MDS analysis indicated a rough grouping of line versus hybrid varieties and suggested that hybrids require more breeding effort to reach the level of tocopherols existed in line varieties.

Mapping of QTL controlling tocopherol content in winter oilseed rape

AbstractTocopherols are natural antioxidants in vegetable oils and are important dietary nutrients. Enhanced tocopherol content has become an important objective in oilseed rape breeding. A segregating DH population was tested for 2 years at two locations in replicated field trials. Genotypic differences occurred for α‐, γ‐ and total tocopherol content as well as α/γ‐tocopherol ratio, but highly significant genotype x environment interactions resulted in low heritabilities. Using a mixed‐model composite interval mapping approach between one and five QTL with additive and/or additive x environment interaction effects could be mapped for α‐, γ‐ and total tocopherol content and α/β‐tocopherol ratio. In addition, one to six locus pairs with epistatic interaction effects were identified, indicating a strong contribution of epistasis to trait variation. In total, the additive and epistatic effects explained between 28% (α‐tocopherol content) and 73% (total tocopherol content) of the genotypic variance in the population, with individual QTL and locus pairs contributing between 7.5 and 29.2% of variance. Considering the low heritabilities of the tocopherol traits, the results of this study indicate that marker‐assisted selection may be an efficient strategy in a breeding program for enhanced tocopherol content in rapeseed.

Synergistic effect of antiwear additives and antioxidants in vegetable oil

AbstractCertain vegetable oils have been recognised as promising candidates for environmentally friendly lubricants. Their lubricity can be optimised using antiwear additives. However, decomposition of the additives, accompanied by auto‐oxidation of the vegetable oils, has been found to occur. In other words, the antiwear additives may degrade in vegetable oils, and give less oxidative stability. In order to understand the mechanism, oxidation testing of a vegetable oil was performed by monitoring the peroxide value (POV). It was observed that POV increases as soon as oxidation starts. The value reached 1400–1500 ppm within 50 h of reaction time. Then it decreased to an equilibrium value of 400–500 ppm within 200 h. Antioxidants to prevent peroxide generation were examined. Phenolic antioxidants and zinc dialkyldithiocar‐bamate exhibited good results with regard to preventing peroxide generation, whereas aromatic amines gave poor results. A synergistic effect that prevents the decomposition of the antiwear additives was found.

Simultaneous determination of ascorbyl palmitate and nine phenolic antioxidants in vegetable oils and edible fats by HPLC

AbstractThis study describes an HPLC method for the simultaneous determination of ascorbyl palmitate (AP) and synthetic phenolic antioxidants (SPA) in vegetable oils and edible fats in a single run. To achieve this, citric acid was used in combination with isoascorbic acid for stabilization of AP in standard and sample solutions and for deactivation of oxidizing agents in the HPLC system. SPA and AP were directly extracted from samples with methanol containing 1 mg/mL each of citric acid and isoascorbic acid. HPLC analytical and guard columns were pretreated with 90% methanol/acetonitrile 1∶1 (vol/vol), containing 4 mg/mL each of citric acid and isoascorbic acid, and 10% water at pH 3, for 30 min. Under these conditions, AP was stable for about 7 h at room temperature. The relative SD of repeatability for AP (0.5–3.6%) was comparable to that for SPA (0.3–2.8%). Average recovery from spiked samples was 100% for AP, 98–103% for SPA, and 85% for BHT (up to 90% using double extraction with methanol).

The Phosphatides of Hevea Brasiliensis

Abstract The presence of phosphatide in Hevea latex had long been suspected, but it was not until 1931 that Rhodes and Bishop isolated phosphatidic material containing 0.59 per cent nitrogen and 1.72 per cent phosphorus from the serum of latex which had been coagulated with ethanol. The crude material of these authors represented 0.2 per cent of the latex and, on treatment with acetone, yielded an insoluble fraction containing 0.88 per cent nitrogen and 2.56 per cent phosphorus (40 per cent of the former product). This latter fraction was, according to the accepted analytical composition of phosphatide, still very impure. The work of Rhodes and Bishop was repeated by Altman and Kraay, who isolated in very small amounts a product which gave much the same analyses, and extended the findings of Rhodes and Bishop by showing that the crude phosphatide contained both choline and glycerophosphoric acid. It is very probable that the phosphatide, although present in such small amount, is one of the important nonrubber components of latex. Judging from the ease with which phosphatides emulsify in aqueous media, there seems little doubt that the phosphatidic material assists in the maintenance of latex as a stable emulsion. It has been suggested by Bollman that crude phosphatide preparations act as natural antioxidants in vegetable oils. This suggestion has been disputed by Diemair and Fox and other workers, who state that this property is not possessed by pure phosphatide, although the complex system from which the phosphatide had been separated was an active antioxidant. Diemair, Strohecker and Reuland have advanced the opinion that the active antioxidant is a protein-phosphatide complex. The present work was undertaken as part of an investigation of the non-rubber components of latex. The crude phosphatide was prepared by the method of Rhodes and Bishop, the preliminary treatment being carried out at the Rubber Research Laboratories, Ceylon, under the direction of Mr. O'Brien, to whom the author's thanks are due. The raw material was treated by the method outlined below. The crude phosphatide was fractionated by a method which was essentially that used by Channon and Foster in their work on the phosphatides of wheat germ. The fractionation resulted in the isolation of a fairly pure form of phosphatidic acid (the possible source of which is discussed later) and an impure form of lecithin. The lecithin fraction contained little or no kephalin (only about 5.5 per cent of the nitrogen in this fraction was amino-nitrogen), a finding which was unexpected.