Synthetic phenolic antioxidants

Among the plant phenols, the flavonoids and the anthocyanidins, belonging to the 1,3-diphenylpropans, have been studied in most detail, mainly because of their potential health benefits. With more than 4,000 different flavonoids known, systematic studies of the effects of variation in molecular structure on physico-chemical properties of importance for antioxidative effects have also been possible (Jovanovic et al, 1994 Seeram and Nair, 2002). Flavonoids were originally found not to behave as efficiently as the classic phenolic antioxidants like a-tocopherol and synthetic phenolic antioxidants in donating... 

BisHov s J, MASUOKA Y and KAPSALis J G (1977) Antioxidant effect of spices, herbs and protein Hydrolyzates in freeze-dried model systems Synergistic action with synthetic phenolic antioxidants, J Foot/ Processing Preservation, 1, 153-66. 

Microcoulometric titration is used as the detection mode in some commercial sulfur-specific analysers. Sulfur in PP and waxes (range from 0.6 to 6 ppm S) were determined by means of an oxidative coulometric procedure [537]. The coulometric electrochemical array detector was used for determining a variety of synthetic phenolic antioxidants (PG, THBP, TBHQ, NDGA, BHA, OG, Ionox 100, BHT, DG) in food and oils [538],... 

In general, antioxidants are divided into natural and synthetic groups. Because natural antioxidants are discussed in other chapters ( The Fat-soluble Vitamins, Analysis of Phenolic Compounds, and Analysis of Organic Acids ), we deal here only with the determination of synthetic phenolic antioxidants (SPA). 

Table 6 Physical Properties of Synthetic Phenolic Antioxidants... 

Table 7 Synthetic Phenolic Antioxidants Approved for Food Use in Various Countries/Communities...

Table 8 Individual Synthetic Phenolic Antioxidants, in Decreasing Order of Polarity...

Andrikopoulos et al. (124) separated triglycerides, together with nine synthetic phenolic antioxidants most commonly used to prevent oxidation of edible oils and fats, as well as the natural antioxidants tocopherol and alpha-tocopherol acetate by HPLC using a reversed-phase Cl8 column and gradient elution with water/acetonitrile/methanol/isopropanol. Except for dilution of the oil with isopropanol/hexane, no further sample preparation was required. Ultraviolet detection was applied. The synthetic antioxidants PG, OG, DG, BHA, TBHQ, BHT, Ionox 100, THBP, and NDGA, as well as alpha- and delta-tocopherol and alpha-tocopherol acetate were separated. 

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. 

Schober and Mittelbach (2004) also investigated the impact of concentration of eleven synthetic phenolic antioxidants on oxidative stability of RME, UCOME and TME) by EN 14112 (Anon., 2003c) and on other relevant fuel... 

Figure 4. Chemical structures of synthetic phenolic antioxidants commonly used in fats and oils.

Natural phenolic antioxidative activity is an additional benefit in the use of these smoke flavourings. The higher boiling point phenolics, in particular, possess antioxidative functionality similar to that of commercially used synthetic phenolic antioxidants. 

Karovicova J and Simko P (2000) Determination of synthetic phenolic antioxidants in food by high performance liquid chromatography. Journal of Chromatography A 882 271-281. 

Despite the great number of antioxidant compounds available, only a few are used in the food industry and their use (especially of synthetic ones) is regulated by national or international authorities, with upper limits for daily intake levels (Takemoto et al., 2009 Andre et al., 2010). The most commonly used are the naturally occurring tocopherols and synthetic phenolic antioxidants, including propyl gallate (PG), butylhydroxyanisole (BHA), butylhydroxytoluene (BHT), and tert-butylhydroquinone (TBHQ). 

FIGURE 13.2 Structures of the synthetic phenolic antioxidants BHA, BHT, and TBHQ. 

Delgado-Zamarreno, M. M., I. Gonzalez-Maza, A. Sanchez-Perez, and R. Carabias Martinez. 2007. Analysis of synthetic phenolic antioxidants in edible oils by micellar electrokinetic capillary chromatography. Food Chem. 100(4) 1722-1727. 

Propyl (PG, E 310), octyl (OG, E 311), and dodecyl (or lauryl) (DG, E 312) esters of gallic acid, usually named alkyl gallates, form a part of the synthetic phenolic antioxidants, mainly used as food additives, with PG being the most frequently used alkyl gallate. The molecular structure of these compounds is composed of a hydrophilic head (phenolic ring) and a hydrophobic alkyl chain (Figure 14.1). PG is slightly soluble in water but OG and DG are insoluble in water. The three compounds are soluble in ethanol, ethyl ether, and oils. 

Gutierrez-Larrainzar, M., J. Rua, D. de Arriaga, P. del Valle, and M. R. Garcia-Armesto. 2013. In vitro assessment of synthetic phenolic antioxidants for inhibition of foodborne Staphylococcus aureus. Bacillus cereus and Pseudomonas fluores-cens. Food Control 30 393-399. 

Synthetic phenolic antioxidants used in food products to prevent or delay lipid oxidation during processing and storage of fats, oils, and lipid-containing foods are propyl gallate (PG), tertiary butyl hydroquinone (TBHQ), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) (Saad et ah, 2007). 

K. M. Talib, and K. Ahmad. 2007. Determination of synthetic phenolic antioxidants in food items using reversed-phase HPLC. Food Chemistry 105(l) 389-394. 

A.W. Kirleis, C.M. Stine, Retention of synthetic phenolic antioxidants in model ffeeze-dried food systems. J. Food Sci. 43(5), 1457-1460 (1978)... 

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