Fats and oils antioxidants

E Graciani-Constante. High-speed liquid chromatography of fat and oil antioxidants. Grasas-y-Aceites 26 150-152,1975. 

The function of an antioxidant is to retard the oxidation of an organic substance, thus increasing the useful life or shelf life of that material. In fats and oils, antioxidants delay the onset of oxidation or slow the rate of oxidizing reactions. Oxidation of lipids chemically produces compounds with different odors and taste and continues to affect other molecules in the food. The main purpose of using an antioxidant as a food additive is to maintain the quality of that food and to extend its shelf life rather than improving the quality of the food. Figure 1 illustrates how antioxidants can affect the quality maintenance of food in terms of oxidative rancidity... 

Uses Antioxidant for fats and oils antioxidant, preservative in foods, cos-... 

Precaution Combustibie Hazardous Decomp. Prods. Heated to decomp., emits acrid and irritating fumes HMIS Health 1, Flammability 1, Reactivity 0 Uses Antioxidant for fats and oils antioxidant, preservative in foods, cosmetics, pharmaceuticals, plastics, food pkg., food-pkg. adhesives, pressure-sensitive adhesives defoamer in food-contact paper/paperboard in lubricants for incidental food-contact use pkg. material for irradiated foods Use Level 0.02% max. (preservation of fixed oils, fats, vitamin oil cones.)... 

Citric acid is used in carbonated beverages to provide tartness, modify and enhance flavors, and chelate trace metals. It is often added to jams and jellies to control pH and provide tartness. It is used in cured and freeze-dried meat products to protect the amino acids (qv) and improve water retention. Bakers use it to improve the flavor of fmit fillings in baked goods. Because citric acid is a good chelator for trace metals, it is used as an antioxidant synergist in fats and oils, and as a preservative in frozen fish and shellfish (7) (see Antioxidaisits). 

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). 

The effectiveness of antioxidants as preservatives for fats and oils is evaluated by determining the rate of peroxide development using the Active Oxygen Method (AOM) (29). The development of a rancid odor is used to evaluate the stabiUty of food items (Schaal Oven StabiUty test) (30). 

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. 

For the group of fats and oils the antioxidants listed in Table 12.10 are used. For fish and fish products (including prawns and shrimps), fmit and vegetable products (including raw peeled potatoes) and meat and meat products (corned, cured, pickled or salted and cooked) only ascorbic acid, eiythorbic acid and their sodium salts may be used. 

The selection of the most suitable antioxidant depends on the character of food and the targets which should be attained. Naturally occuring fats and oils contain indigenous antioxidants that protect the unsaturated lipids from free-radical destruction in their native vegetable and animal sources. On the other hand, fats and oils exist in a commingled fashion with reactive substances which cause their rapid decomposition. Intensity of oxidative alterations is also influenced by the shelf-life of products and storage conditions. All these facts should be considered when deciding whether any and if so what antioxidant will be used. 

BHA Antioxidant (0.01% w/v) Prevents oxidation of fats and oils and is frequently used in combination with BHT or citric acid. Trace quantities of metals and exposure to light cause discoloration and loss of activity... 

Hydroquinone is used as a photographic developer (with black-and-white film), a dye intermediate, a stabilizer in paints, varnishes, motor fuels and oils, an antioxidant for fats and oils, an inhibitor of polymerization and in the treatment of skin hyperpigmentation (Lewis, 1993). 

ANTIOXIDANTS. Usually an organic compound added to various types of materials, such as rubber, natural fats and oils, food products, gasoline, and lubricating oils, for the purposes of retarding oxidation and associated deterioration, rancidity, gum formation, reduction in shelf life, etc. 

A special type of polymeric antioxidant is anoxomer, which consists of 1,4-benzenediol, 2-(l,l-dimethylethyl)-polymer with diethylbenzene, 4-(l,l-dimethyl-ethyl)phenol, 4-methoxy-phenol, 4,4 -(l-methylethylidene)bis(phenol), and 4-methylphenol prepared by condensation polymerization of divinylbenzene (m- and p-) with tert-butylhydroquinone, tert-butylphenol, hy-droxyanisole, p-cresol, and 4,4 -isopropylidenediphenol. Total monomers, dimers, and trimers below 500 are not more than 1%. Anoxomer is permitted in the United States as an antioxidant in food at a level of not more than 5 ppm of fat and oil content of the food. 

Antioxidants for fats and oils function by interfering in the formation of the free radicals that initiate and propagate oxidation. Knowledge of the mechanism of antioxidant performance reinforces several important aspects of antioxidant usage. 

Antioxidants must be added to fats, oils, and food products as early as possible for maximum benefit. The addition of antioxidants to fats and oils with a substantial peroxide content will result in a loss of antioxidant performance. 

Antioxidants have to form stable low-energy free radicals that will not further propagate the oxidation of fats and oils. From this point of view, the most convenient compounds are the phenolic compounds, which structure allows them to form low-energy radicals through stable resonance hybrids, as follows ... 

J Anderson, PJ van Niekerk. High-performance liquid chromatography determination of antioxidants in fats and oils. J Chromatogr 394 400-402, 1987. 

Yamaguchi, N. Yokoo, Y. Fujimaki, M. Studies on antioxidative activities of amino compounds on fats and oils. III. Antioxidative activities of soybean protein hydrolyzates and synergistic effect of hydrolyzate on tocopherol. Nippon Shokuhin Kogyo Gakkaishi 1975, 22, 431-5. 

Increased reducing power, i.e., increased antioxidant activity or more negative redox potential, is also one of the symptoms of the Maillard reaction (see Chapter 1). This has considerable significance, because, as far as foods are concerned, one of the main ways in which they deteriorate chemically is through oxidation, particularly of unsaturated fats and oils, leading to oxidative rancidity. The topic has considerable physiological significance as well (see Chapter 8). 

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