Commonly Used Antioxidants in Foods

There are numerous synthetic and natural compounds called antioxidants which regulate or block oxidative reactions by quenching free radicals or by preventing free-radical formation. Vitamins A, C, and E and the mineral selenium are common antioxidants occurring naturally in foods (104,105). A broad range of flavonoid or phenoHc compounds have been found to be functional antioxidants in numerous test systems (106—108). The antioxidant properties of tea flavonoids have been characterized using models of chemical and biological oxidation reactions. 

Di-/ l -butyl-4-methylphenol /2j5 i77-2/-i72,6-Di-/ l -butyl-4-methylphenol (di-/ l -butyl-/)-cresolDi-/ l -butyl-j )-cresol or butylated hydroxytoluene (BHT)) is most commonly used as an antioxidant in plastics and mbber. Use in food is decreasing because of legislation and it is being replaced by butylated hydroxy anisole (BHA) (see Antioxidants Eood additives). 

Table 12.1 presents the most common antioxidants permitted for use in food products. 

Butylatedhydroxyamsole (BHA) was first used in food products in 1940. This continues as one of the commonly used antioxidants, sometimes in combination with butylated hydroxytoluene (BHT), propyl gallate, citric, or phosphoric acids, to obtain a synergistic effect. In foodcontact surfaces. BHT has been used by itself or in combination with thiodipropionates and/or phosphoric acids, to obtain a synergistic effect. Well over 50 million of antioxidants are produced per year commercially in the United Slates alone. 

Enzyme Preparations used in food processing are derived from animal, plant, or microbial sources (see Classification, below). They may consist of whole cells, parts of cells, or cell-free extracts of the source used, and they may contain one active component or, more commonly, a mixture of several, as well as food-grade diluents, preservatives, antioxidants, and other substances consistent with good manufacturing practices. 

Another class of secondary antioxidants used in food contact plastics is thioether. The most common examples used in polypropylene, polystyrene and PVC are thiodipropanoic acid, didodecyl ester (DLTDP) and thiodipropanoic acid, dioctadecyl ester (DSTDP). Thioethers react with hydroperoxides to form sulphoxides as shown in Fig. 10.8. 

The most common antioxidants permitted for use in foods in most countries are shown in Table 8. Table 9 presents the ADI of some antioxidants allocated by the Joint FAOAVHO Expert Committee on Food Additives (JECFA). The food producer has full responsibility for the choice of suitable antioxidants according to the corresponding guidelines governed by regulatory laws of the individual country or the international bodies that declare their safety (64). 

Autoxidation can be inhibited or retarded by adding low concentrations of chainbreaking antioxidants that interfere with either chain propagation or initiation (286). Chain-breaking antioxidants include phenolic and aromatic compounds hindered with bulky alkyl substituents. Common synthetic chain-breaking antioxidants used in food lipids include butylated hydroxyanisole (BHA), butylated hydroxyto-luene (BHT), ferf-butyUiydroquinone (TBHQ), and propyl gallate (PG). This class of antioxidants react with peroxy free radicals to terminate reaction chains. The antioxidant radical (A ) formed in Equation 5 should be relatively stable and unable to initiate or propagate the oxidation chain reaction. 

Products and Uses Both are antioxidants commonly added in small amounts to food, particularly to oils and fats, as preservatives. Also used as preservative in rubber and plastics. Recent claims have been made that they inhibit cancers in lab animals, prevent herpes and other viruses, and increase life spans. There has been no scientific research to prove these theories. 

Fish oils contain a wide range of fatty acids from C14 to C26 in chain length with 0-6 double bonds. The major acids include saturated (14 0, 16 0, and 18 0), monounsaturated (16 1, 18 1, 20 1, and 22 1) and n-3 polyene members (18 4,20 5,22 5, and 22 6). Fish oils are easily oxidized and are commonly used in fat spreads only after partial hydrogenation. However, they are the most readily available sources of n-3 polyene acids, especially, EPA and DHA, and with appropriate refining procedures and antioxidant addition these acids can be conserved and made available for use in food. The long-chain polyene acids are valuable dietary materials and there is a growing demand for high quality oil rich in EPA and DHA. °... 

Phosphoric acid INS No 338, FW 98 other chemical name orthophosphoric acid. Phosphoric acid is an inorganic acid, the second most common acidifier (after citric acid—60%) used iu the food industry—around 25% with its salts. All other acidifiers together account for 15% [9]. Phosphoric acid can be used in foods as an acidulant, sequestrant, and antioxidant synergist. The quantity used varies in a broad range of 1-20 g/kg (up to 2g/L in beverages). No ADI has been established for phosphoric acid, however the maximum tolerable daily intake (MTDI) from all sources is limited to 70mg/kg dw. 

Details A solid in flake, crystal or dust form. Used in production of epoxy-phenolic resins, monomer of polycarbonates (PC), an antioxidant for PVC, and as an inhibitor used during PVC polymerisation. PC are widely used in many consumer products, from sunglasses and CD to water and food containers and shatter-resistant baby bottles. Some polymers can also contain bisphenol A, and epoxy resins containing bisphenol A are common coatings used in food cans. 

The most common simple phenolic is butylated hydroxytoluene (BHT) or 2,6-di-t-butyl-4-methylphenol. BHT possesses broad FDA approval and is widely used as an antioxidant in a variety of polymers. It is commonly called the workhorse of the industry but is losing ground to the higher molecular weight antioxidants which resist migration. The disadvantage of BHT is that it is highly volatile and can cause discoloration. Other simple phenolics include BHA (2- and 3-t-butyl-4-hydroxyanisole) which is frequently used in food applications. 

Amperometry is probably one of the most common electroanalytical techniques used in food analysis and there are numerous examples in the literature. Among others, it is worth mentioning analysis of cholesterol [72], vitamins [73, 74], carbohydrates [75, 76], antioxidants [4, 77-79], pesticides [80, 81], and toxins [82]. It is also important to point out that, although not discussed in this chapter, the same instrumental configuration used in amperometry can be used for the development of amperometric biosensors [83-86], electrochemical ELISA assays [87-89], and electrochemical tongues [90,91]. 

Polyphenols are commonly present in fruits, vegetables, nuts, seeds, and flowers. Moreover, polyphenols can be found in such products as cocoa, tea, coffee, wine, jam, and chocolate. Polyphenolic compounds are also often applied in cosmetics, medicines, pharmaceuticals, dietary supplements, and in recent years, for the production of functional foods. The food industry offers a variety of new functional products in which the polyphenol content is usually higher than in products of natural origin. Milk enriched with soy isoflavones, chocolate enriched in procyanidins, drinks with higher amounts of anthocyanins, functional drinks enriched with extracts of tea—these are just a few products that are the result of functional foods revolution. On the other hand, the use of synthetic antioxidants in the food industry is of great concern among consumers who seek to limit their intake. Toxicological and nutritional research indicates adverse effect of some synthetic antioxidants used in food. The use of additives in food products, mainly in edible fats, means that more attention should be paid to antioxidants that are derived from natural plant extracts and used as food additives. 

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