Antioxidant natural

The unsaturated lipids in living tissue are relatively stable. Plants and animals have the necessary complement of antioxidants and of enzymes, for instance, glutathione peroxidase and superoxide dismutase, to effectively prevent lipid oxidation. 

During the isolation of oil from plants (cf. 3.8.3), tocopherols are also isolated. A sufficient level is retained in oil even after refining, thus, toco- 

Storage at low temperature in the dark. The autoxidation rate is thereby decreased substantially. However, in fruits and vegetables which contain the lipoxygenase enzyme, these precautions are not applicable. Food deterioration is prevented only after in activation of the enzyme by a blanching process (cf. 2.6.4). 

The antioxidant activity of tocopherols increases from a 5. It is the reverse of the vitamin E activity (cf. 6.2.3) and of the rate of reaction with peroxy radicals. Table 3.39 demonstrates that a-tocopherol reacts with peroxy radicals faster than the other tocopherols and the synthetic antioxidants DBHA and BHT. 

In the reaction with peroxyl radicals, the higher rate of tocopherols compared with DBHA (cf. Table 3.39) is based on the fact that the chromanoxyl radical formed on H-abstraction is more stable than the phenoxyl radical. Both types of radical are stabilized by the following resonance  

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Tocotrienols differ from tocopherols by the presence of three isolated double bonds in the branched alkyl side chain. Oxidation of tocopherol leads to ring opening and the formation of tocoquinones that show an intense red color. This species is a significant contributor to color quaUty problems in oils that have been abused. Tocopherols function as natural antioxidants (qv). An important factor in their activity is their slow reaction rate with oxygen relative to combination with other free radicals (11). 

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). 

Plasticity Retention Index. The oxidation behavior of natural mbber may affect both the processing characteristics and final vulcanizate performance, and the plasticity retention index (PRI) test can be used to give an indication of both. Natural antioxidants present in natural mbber give some protection and a measure of the efficacy of protection is given by PRI. PRI% = P q j Pq x 100, where Pq is the initial Wallace plasticity and P q is the... 

The aims of the given work ar e investigation of interaction processes of active forius of oxygen with phospholipids under action of natural antioxidant QIO development of chemical model on the basis of physical and chemical behaviour of QIO and corresponding mathematical model. 

As the above mentioned studies with high supplementation dosages exemplarily show, there is no known toxicity for phylloquinone (vitamin Kl), although allergic reactions are possible. This is NOT true for menadione (vitamin K3) that can interfere with glutathione, a natural antioxidant, resulting in oxidative stress and cell membrane damage. Injections of menadione in infants led to jaundice and hemolytic anemia and therefore should not be used for the treatment of vitamin K deficiency. 

In the last few decades, several epidemiological studies have shown that a dietary intake of foods rich in natural antioxidants correlates with reduced risk of coronary heart disease particularly, a negative association between consumption of polyphenol-rich foods and cardiovascular diseases has been demonstrated. This association has been partially explained on the basis of the fact that polyphenols interrupt lipid peroxidation induced by reactive oxygen species (ROS). A large body of studies has shown that oxidative modification of the low-density fraction of lipoprotein (LDL) is implicated... 

CHOPRA M, MCLOONE u L, o neill m, WILLIAMS N and THURNHAM DI (1996) Fruit and vegetable supplementation - effect on ex vivo LDL oxidation in hiunans , in Kumpulainen, J T and Saonen, J T (eds), Natural Antioxidants and Food Quality in Atherosclerosis and Cancer Prevention, Cambridge, Royal Society of Chemistry, 150-55. 

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. 

WANG H, CHEN R and XU X (1995) Technology of the preparation of highly active natural antioxidant from tea , JTea Sci, 15 (1), 49-56. 

YANG X Q, WANG Y F and XU F (1995) Natural antioxidant tea polyphenols application on oil and food Study on inhibiting the deterioration of salad oil and instant noodles , J UnivAgric Zhejiang, 21 (5), 513-18. 

In inner layers, changes are much the same as during boiling. Tocopherols and tocotrienols present in wheat and rye are partially destroyed during baking. In ordinary wheat bread, losses of a-tocopherol amount to about 25%, but in the case of rye bread, prepared by traditional technology, a loss of about 50% was reported (Piironen et al, 1987). Losses of natural antioxidants in coffee brews and tomato puree were also observed (Nicoli et al, 1997). 

Meat products have to be stabilised in some cases, as meat lipids contain no natural antioxidants or only traces of tocopherols. Most muscle foods contain, however, an efficient multi-component antioxidant defence system based on enzymes, but the balance changes adversely on storage. The denaturation of muscle proteins is the main cause of the inbalance as iron may be released from its complexes, catalysing the lipid oxidation. Salting contributes to the negative effects of storage, as it enhances oxidation. Using encapsulated salt eliminates the deleterious effect of sodium chloride. 

It is not only lipids but also essential oils which are sensitive to oxidative changes on storage. Sometimes stabilised by synthetic or natural antioxidants, they usually contain substances showing moderate antioxidant activity, but these may be lost by evaporation or oxidised by air oxygen unless more powerful phenolic antioxidants are added. 

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. 

The most common natural antioxidants are tocopherols, ascorbic acid and P-carotene (more often synthetic nature-identical compounds than natural products). Their changes were studied in detail in model systems, fats and oils, but experimental evidence is mainly lacking on more complicated systems, such as natural foods and ready dishes. Still less is known on different antioxidants from spices and from essential oils. These data will probably be obtained gradually. Very little is known about synergism of antioxidants in food products other than edible fats and oils or their regeneration from the respective free radicals and quinones. In mixtures, some antioxidants are preferentially destroyed and others are saved. Some data have already been published, but these complex changes should be studied in more detail. 

PACKER I, TRABER M G and xiN w (1996) Proceedings of the International Symposium on Natural Antioxidants, Champaign, IL, AOCS Press. 

SHAHiDi F (1996) Natural Antioxidants, Champaign, IL, AOCS Press. 

SHAHiDi F and NACZK M (1993) Food Phenolics, Lancaster, P A, Technomic Publishers. YANISHLIEVA N V and MARINOVA E M (2001) Stabilisation of edible oils with natural antioxidants , Eur J Lipid Sci Technol, 103 (11) 752-67. 

Optimising the use of phenolic compounds in foods 317 16.1.2 Classifying natural antioxidants... 

Natural antioxidants may be classified according to their nutritive value or according to their solubility. The hydrophobic vitamin E and the hydrophilic vitamin C are thus important both as nutrients and as antioxidants. The nonnutritive antioxidants may similarly be divided into lipid-soluble and water-soluble antioxidants, as shown in Fig. 16.3, which will also form the basis for a discussion of exploitation of combinations of anhoxidants in order to improve protective effects. 

CHANG s s, osTRic-MATiJASEVic B, HSIEH o A L and HUANG c L (1977) Natural antioxidants from rosemary and sage, J Food Sci, 42 (4), 1102-6. 

JASWIR I, MAN Y B c and KITTS D D (2000) Use of natural antioxidants in refined pahn olein during repeated deep-fat frying, Food Res Int, 33, 501-8. 

LIN J K s, LEE F, HUANG Y T, LiN-SHiAU s Y (1995) Signal transduction and oncogene expression mediated by reactive oxygen species. In Proceedings of the International Symposium on Natural Antioxidants - Molecular Mechanisms and Health Effects. Eds Packer, L, Traber, M G, Xin, W Champaign, I L, USA AOCS Press, 303-19. 

Lafferty, J., Truscott, T.C., and Land, E.J., Electron transfer reactions involving chlorophylls a and b and carotenoids, J. Chem. Soc. Farad. Trans., lA, 2760, 1978. Burri, B.J., Clifford, A.J., and Dixon, Z.R., Beta-carotene depletion and oxidative damage in women, in Natural Antioxidants and Anticarcinogens in Nutrition, Health and Disease, Kumulainen, J.T. and Salonen, J.T., Eds., Royal Society of Chemistry, Stockholm, 1999, 231. 

Lairon, D. and Amiot, M.J., Flavonoids in food and natural antioxidants in wine, Curr. Opin. Lipidol., 10, 23, 1999. 

Many different methods have been used to evaluate the antioxidant capacities of isolated molecules, carotenoids, and other natural antioxidants and of foods and food extracts containing antioxidants. It is not the purpose of this chaper to review all the methods, but some general points can be made. First, when using only one test to evaluate the antioxidant capacities of carotenoids, one should be very careful in the interpretation of obtained data. Indeed, different results can be obtained with different tests applied to the same molecules. At least two different methods should be used to evaluate the antioxidant activity of a molecule or a food extract. " Second, lipophilicity is an important factor to consider in testing the antioxidant activities... 

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