Antioxidant, carotene synthetic

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. 

The structures of four of the synthetic carotenoids (beta-carotene, canthaxanthin, beta-apo-8 -carotenol, beta-apo-8 -carotenoic acid) are shown in Fig. 8.2. By virtue of their conjugated double bond structure, they are susceptible to oxidation but formulations with antioxidants were developed to minimize oxidation. Carotenoids are classified as oil soluble but most foods require water soluble colorants thus three approaches were used to provide water dispersible preparations. These included formulation of colloidal suspensions, emulsification of oily solutions, and dispersion in suitable colloids. The Hoffman-LaRoche firm pioneered the development of synthetic carotenoid colorants and they obviously chose candidates with better technological properties. For example, the red canthaxanthin is similar in color to lycopene but much more stable. Carotenoid colorants are appropriate for a wide variety of foods.10 Regulations differ in other countries but the only synthetic carotenoids allowed in foods in the US are beta-carotene, canthaxanthin, and beta-8-carotenol. 

Liang et al. (2006) investigated the effect of natural and synthetic antioxidants on oxidative stability of crude and distilled palm oil FAME (PME). Crude palm oil contains minor components such as carotenes and a-toco-pherols that upon transesterification, yields crude PME that exhibit superior oxidative stability (OSI > 25h) compared to distilled PME (OSI - 3.5h), which does not contain minor components. Liang and colleagues therefore endeavored to improve the oxidative stability of distilled PME so that it meets the minimum OSI = 6h as specified in EN 14214 (Anon., 2003b). Natural (a-tocopherol) and synthetic (BHT and TBHQ) antioxidants were investigated in distilled PME. It was discovered that both natural and synthetic antioxidants exhibited beneficial effects on the oxidative stability of distilled PME... 

The most widely used antioxidants are free radical scavengers that remove reactive radicals formed in the initiation and propagation steps of autoxidation. A number of natural or synthetic phenols can compete, even at low concentrations, with lipid molecules as hydrogen donors to hydroperoxy and alkoxy radicals, producing hydroperoxides and alcohols and an unreactive radical. (3-carotene reacts with per-oxy radicals, producing a less-reactive radical. These stabilized radicals do not initiate or propagate the chain reaction. 

The lipidic vitamins (ref.84) include vitamin A (32), a substance intrinsic to the physiology of vision, vitamin E (83), a natural protective antioxidant, and vitamins K, (84) with Kj (85), antihemorrhagic compounds, each of which is derivable from an initial natural product intermediate. Although traditionally a -ionone obtained from citral (a major constituent of lemon grass oil) was used for the synthesis of vitamin A, a synthetic source has now replaced this in a process which also gives /g-carotene. In one method the Cl4 aldehyde in that process is reacted with a C6 eneyne component and selective hydrogenation followed by dehydration and isomerisation affords the final product (ref.85). 

Well-known naturally occurring antioxidants are vitamin C (ascorbic acid), which are contained in many citrus fruits, or on the other hand manbers of vitamin E family, which appear for example in nnts and snnflower seeds. Also P-carotene and lycopine, which also belong to the family of caro-tenoides, are further examples of natural antioxidants. On the other hand, there are many synthetic... 

The lipid peroxidation inhibitory activities of EOs are assessed by the P-carotene bleaching tests (Yadegarinia et al., 2006). In this method, the ability to minimize the coupled oxidation of P -carotene and linoleic acid is measured with a photospectrometer. The reaction with radicals shows a change in this orange color. The P-carotene bleaching test shows better results than the DPPH assay because it is more specialized in lipophilic compounds. The test is important in the food industry because the test medium is an emulsion, which is near to the situation in food, therefore allowable alternatives to synthetic antioxidants can be found. An only qualitative assertion uses the TLC procedure. A sample of the EOs is applied onto a TLC plate and is sprayed with P-carotene and linoleic acid. Afterwards, the plate is abandoned to the daylight for 45 min. Zones with constant yellow colors show an antioxidative activity of the component (Guerrini et al., 2006). 

Amarowicz et al. (2000) and Matthaus (2002) investigated the effect of rapeseed phenolics on radical scavenging. The antioxidant activity of ethanolic (95%) extract of rapeseed meal towards the oxidation of rapeseed oil was better than that of some widely used synthetic antioxidants (Wanasundara and Shahidi, 1994). Phenolic compounds present in crude rapeseed oil have also shown antioxidant properties (Koski et al., 2003) in bulk and emulsified methyl linoleate and lecithin-liposome systems. Amarowics et al. (2003) investigated the antioxidant activity of phenolic fractions of rapeseed (total three fractions) using a P-carotene-linoleate model system and enhanced chemiluminescence and photochemiluminescence methods. A measure... 

The nature of the supplements used It has been suggested that the synthetic forms used in most trials may have different biological activity or potency from natural forms of these vitamins, although trials using the natural forms have not found different clinical effects. The type of isomer used has also been questioned (e.g., /3-carotene versus other carotenoids such as lycopene or lutein or a-tocopherol versus 7-tocopherol). Trials have not investigated other potentially beneficial antioxidants in foods, such as flavonoids and lycopenes. 

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