Antioxidants in Food

Toluenesulfonic Acid. Toluene reacts readily with fuming sulfuric acid to yield toluene—sulfonic acid. By proper control of conditions, /)i7n7-toluenesulfonic acid is obtained. The primary use is for conversion, by fusion with NaOH, to i ra-cresol. The resulting high purity i7n -cresol is then alkylated with isobutylene to produce 2 (i-dii-tert-huty -para-cmso (BHT), which is used as an antioxidant in foods, gasoline, and mbber. Mixed cresols can be obtained by alkylation of phenol and by isolation from certain petroleum and coal-tar process streams. 

The activity of antioxidants in food [ 1 ] emulsions and in some biological systems [2] is depends on a multitude of factors including the localisation of the antioxidant in the different phases of the system. The aim of this study is determining antioxidant distributions in model food emulsions. For the purpose, we measured electrochemically the rate constant of hexadecylbenzenediazonium tetrafluorborate (16-ArN,BF ) with the antioxidant, and applied the pseudophase kinetic model to interpret the results. 

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. 

POKORNY J, YANISHLIEVA N and GORDON M (2001) Antioxidants in Food, Cambridge, Woodhead Publishing. 

Knowledge of the identity of phenolic compounds in food facilitates the analysis and discussion of potential antioxidant effects. Thus studies of phenolic compounds as antioxidants in food should usually by accompanied by the identification and quantification of the phenols. Reversed-phase HPLC combined with UV-VIS or electrochemical detection is the most common method for quantification of individual flavonoids and phenolic acids in foods (Merken and Beecher, 2000 Mattila and Kumpulainen, 2002), whereas HPLC combined with mass spectrometry has been used for identification of phenolic compounds (Justesen et al, 1998). Normal-phase HPLC combined with mass spectrometry has been used to identify monomeric and dimeric proanthocyanidins (Lazarus et al, 1999). Flavonoids are usually quantified as aglycones by HPLC, and samples containing flavonoid glycosides are therefore hydrolysed before analysis (Nuutila et al, 2002). 

LOLIGER J (1991) The use of antioxidants in foods, in Aruoma Ol, HalliweU B Free Radicals and Food Additives, Traylor Francis, London, 121-50. 

PORTER w L (1993) Paradoxical behaviour of antioxidants in food and biological systems, in Williams GM Antioxidants Chemical, Physiological, Nutritional and Toxicological A. ipects, Princeton Scientific, Princeton, N J, 93-122. 

Vinson, J.A. et al., Determination of quantity and quality of polyphenol antioxidants in foods and beverages, Meth. EnzymoL, 335, 103, 2001. 

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. 

The use of antioxidants in food products is governed by regulatory laws of the individual country or by internal standards. Even though many natural and synthetic compounds have antioxidant properties, only a few of them have been accepted as generally recognised as safe (GRAS) substances for use in food products by international bodies such as the Joint FAOAVHO Expert Committee on Food Additives (JECFA) and the European Community s Scientific Committee for Food (SCF). 

The substances which can be used generally as antioxidants in food processing are listed in Table 12.4. 

The application of antioxidants in foods for infants and young children and for particular nutritional needs is regulated by Directive 89/398/EEC. Antioxidants permitted in weaning foods for infants and young children in good health are listed in Table 12.8. 

Sodium, potassium, and calcium salts of ascorbic acids are called ascorbates and are used as food preservatives. These salts are also used as vitamin supplements. Ascorbic acid is water-soluble and sensitive to light, heat, and air. It passes out of the body readily. To make ascorbic acid fat-soluble, it can be esterified. Esters of ascorbic acid and acids, such as palmitic acid to form ascorbyl palmitate and stearic acid to form ascorbic stearate, are used as antioxidants in food, pharmaceuticals, and cosmetics. 

The use of antioxidants in foods, pharmaceuticals, and animal feeds (direct feed additives), as well as their use in food-contact surfaces (indirect additives) is closely regulated by the governments of several countries. Antioxidants are approved only after extensive extraction, toxicological, and feeding studies. The list is relatively limited. Although antioxidants have been used for several decades and some occur naturally in food substances, intensive lesearch in continuing, pardy accelerated by the growing use of unsaturated oils in numerous food products. 

BH Chen, SC Fu. Simultaneous determination of preservatives, sweeteners and antioxidants in foods by paired-ion liquid chromatography. Chromatogr 41(1/2) 43-50, 1995. 

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. 

DR McCabe, IN Acworth. Determination of synthetic phenolic antioxidants in food using gradient HPLC with electrochemical array detection. Am Lab News 30(13) 18B, 18D, 16, 1998. 

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