Antioxidants synthetic

The commonest synthetic antioxidants are butylated hydroxyanisole (BHA) and butylated hydroxy toluene (BHT). Other synthetic antioxidants are w-propyl gallate and n-octyl gallate. Any substance that can act as a radical trap will have antioxidant properties. There are strict rules governing the use of antioxidants in foods. Only those substances that are on the permitted list can be used. 

In order to be used as an antioxidant, a synthetic compound has to meet the following requirements it should not be toxic it has to be highly active at low concentrations (0.01-0.02%) it has to concentrate on the surface of the fat or oil phase. Therefore, strongly lipophilic antioxidants are particularly suitable (with low HLB values, e. g. BHA, BHT or tocopherols, dodecylgallate) for o/w emulsions. On the other hand, the more polar antioxidants, such as TBHQ and propyl gallate, are very active in fats and oils since they are enriched at the surface of fat and come in contact with air. Antioxidants should be stable under the usual food processing conditions. This stability is denoted as the carry through effect. Some of the synthetic antioxidants used worldwide are  

Commercial BHA is a mixture of two isomers, 2- and 3-tert-butyl-4-hydroxyanisole 

ESR spectroscopy has demonstrated that a large portion of ethoxyquin is present in oil as a free radical 

The efficiency of an antioxidant can be evaluated by a comparative assay, making use of an antiox-idative factor (AF)  

the efficiency of an antioxidant increases with an increase in the AF value. As illustrated by the data in Table 3.41, BHA in comparison with BHT shows a higher efficiency in a lard sample. This result is understandable since in BHT both tertiary butyl substituents sterically hinder the reaction with radicals to a certain extent (reaction 1 in Fig. 3.35). The effect on antioxidants depends not only on the origin of fat or oil but, also, on the processing steps used in the isolation and refining procedures. Hence, data in Table 3.41 serve only as an illustration. 

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Antioxidants (qv) have a positive effect on oils when present in the proper concentration. Sterols and tocopherols, which are natural antioxidants, may be analy2ed by gas-Hquid chromatography (glc), high performance Hquid chromatography (hplc), or thin-layer chromatography (tic). Synthetic antioxidants maybe added by processors to improve the performance or shelf life of products. These compounds include butylatedhydroxyanisole (BHA), butylated hydroxytoluene (BHT), / fZ-butyUiydroquinone (TBHQ), and propyl gallate. These materials may likewise be analy2ed by glc, hplc, or tic. Citric acid (qv), which functions as a metal chelator, may also be deterrnined by glc. 

Both synthetic and natural antioxidants exist. The most commonly used synthetic antioxidants include butylatedhydroxyanisole [25013-16-5]... 

The most popular natural antioxidants on the market are rosemary extracts and tocopherols. Natural antioxidants have several drawbacks which limit use. Tocopherols are not as effective ia vegetable fats and oils as they are ia animal fats. Herb extracts often impart undesirable colors or flavors ia the products where used. In addition, natural antioxidants cost considerably more than synthetic ones. Despite this, the pubHc s uncertainty of the safety of synthetic antioxidants continues to fuel the demand for natural ones (21). 

Pharmacology, chemistry, and technology of medicines on the basis of synthetic antioxidants, derivatives of 3-hydroxypyridine and 5-hydroxynicotinic acid 98MI59. 

The effectiveness of tea polyphenols as antioxidants in elastomeric mixes was evaluated and comparison was made with standard styrenated phenol-based antioxidant [45]. The data showed that thermal and oxidative aging resistance was comparable for both natural and synthetic antioxidants. 

No unequivocal unique function for vitamin E has been defined. However, it does act as a hpid-soluble antioxidant in cell membranes, where many of its functions can be provided by synthetic antioxidants. Vitamin E is the generic descriptor for two famihes of compounds, the tocopherols and the tocotrienols (Figure 45—5). The different vitamers (compounds having similar vitamin activity) have different biologic potencies the most active is D-a-tocopherol, and it is usual to express vitamin E intake in milhgrams of D-a-tocoph-erol equivalents. Synthetic DL-a-tocopherol does not have the same biologic potency as the namrally occurring compound. 

Antioxidants are not important only to the health conscious food manufacturers also rely on these chemicals to maintain the shelf life of their products. Synthetic antioxidants such as butylated hydroxyanisole, butylated hydroxytoluene, propyl gallate and tert-butyl hydroquinone were widely used in food processing to control oxidation and maintain food quality. However, as these synthetic antioxidants are suspected to be carcinogenic they now have restricted use in food (Madahavi and Salunkhe, 1995). Therefore, natural antioxidant sources, especially of plant origin, are of great interest to the food industry. 

Synthetic antioxidants are safer, cheaper and purer than natural antioxidants but, nevertheless, the majority of consumers still prefer natural antioxidants. This trend will surely persist in the near future. The mechanisms for the changes of synthetic antioxidants are well known, but the same cannot be stated in the case of natural phenolic antioxidants. They are usually pyrocatechol or pyrogallol derivatives, where the changes during oxidation could be different from those of synthetic antioxidants, which are mostly 1,4-substituted. 

MEDINA I, SATUE-GRACIA M T, GERMAN J B and FRANKEL E N (1999) Comparison of natural polyphenol antioxidants from extra virgin olive oil with synthetic antioxidants in tuna lipids during thermal oxidation, JAgric Food Chem, 47, 4873-9. 

Administration of synthetic antioxidants and/or chelating agents that suppress iron ion-dependent free-radical reactions. Some enzyme inhibitors may be appropriate here, for example, xanthine oxidase inhibitors. 

Direct liquid injection (DLI) has been used even less. Hirter et al. [579] have reported the early analysis of a synthetic antioxidant mixture (Irganox 1010/1076/1098) by means of iRPLC-DLI-QMS with Cl. In early studies, the HPLC effluent was vaporised by laser radiation [593] both El and solvent-mediated Cl spectra were obtained in the on-line mode from analytically difficult molecules. However, the instrumentation was complex the sensitivity was not as good as that obtained by GC-MS and thermal decomposition was observed with other compounds. This direct introduction approach with enrichment was used for the analysis of phthalates. 

Figure 10 presents the results of assay of VE and ACL in blood plasma of rabbits treated with probucol and two other synthetic antioxidants (S-l, S-2) for 4 weeks. In addition to an improvement in antioxidative blood plasma protection, in the case of compound S-2 a statistically significant (p < 0.01) decrease in vitamin E content was detected, a finding considered physiologically unfavorable. 

Tocopherols are not as effective as antioxidants as the synthetic antioxidants, e.g. BHA or BHT. The antioxidant effect of tocopherols is increased by mixing them with ascorbyl palmitate, ascorbic acid, lecithin or citric acid. Typical confectionery applications are the use of tocopherols with ascorbyl palmitate or lecithin or citric acid in the fat phase of toffees or caramels. Chewing gum base can be treated with a- and y-tocopherol to extend the shelf life. 

Synthetic antioxidants, 12 60, 10 828 Synthetic-based fluids (SBF), 9 6 Synthetic-based muds, 9 6 Synthetic-based oil soluble sulfonates,... 

Since food additives are subjected to the most stringent toxicological testing procedures, only a few synthetic antioxidants have been used in foods for any length of time. Antioxidants are extensively tested for the absence of carcinogenity and other toxic effects in themselves, in their oxidised forms, and in their reaction products with food constituents, for their effectiveness at low concentrations, and for the absence of the ability to impart an unpleasant flavour to the food in which they are used. 

New toxicological data on some of the synthetic antioxidants cautioned against their use. In the recent past, natural antioxidants attracted the attention of many food manufacturers as a result of the necessity to produce healthy foods. Numerous antioxidative efficacious compounds that are found in animal or plant tissues and that are also available as synthetic molecules are used in several food applications. Herbs and spices occupy a special position in foods as traditional food ingredients and hence are appropriately used directly for their antioxidant characteristics. If they are applied to foods, they do not need to be declared as antioxidants. 

There are some differences in the regulation of US and EU antioxidants. The restrictions on synthetic antioxidants are more strict in the EU, e.g. TBHQ, THBP, anoxomer, ethoxyquin, guaiac resin and derivates of thiodipropionic acid are not permitted there. On the other hand, sulphur dioxide and sulphites, citric and tartaric acids and their salts and salts of EDTA are not listed as permitted antioxidants in the US. 

Naturally occurring antioxidants are present in many plants and trees such as hevea rubber. The first synthetic antioxidants were synthesized independently by Caldwell and by Winkelman and Gray by the condensation of aromatic amines with aliphatic aldehydes. 

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