Antioxidant Activity in Foods

As previously mentioned, tocopherols/tocotrienols may be added to foods for the stabilization of their polyunsaturated fatty acids. Chemical conditions and the physical state of the food to be stabilized have a major influence on lipid oxidation and antioxidant reactions. The number of possible reaction routes and stabilizing and destabilizing factors is enormous (e.g., Pokorny, 1987 Warner, 1997 Frankel, 1998). In foods, tocopherols can be regenerated from their tocopheroxyl radicals by reducing compounds such as ascorbic acid. Regeneration is possible only if the lipid-soluble tocopheroxyl radical and the water-soluble ascorbic acid are close enough to be able to react with each other, e.g., in emulsion. Thus, the interfacial region between lipid and water phases is important for the antioxidant action of tocopherols and tocotrienols (Frankel, 1998). 

Kinetic studies have confirmed that a-tocopherol is the most efficient antioxidant toward peroxyl radicals (Burton et al., 1985). The order of reaction rates is a- (1- y- 8-vitamer. Because a-tocopherol is the most reactive vitamer, it is also the unstable one and is consumed first among all vitamin E compounds. This disputes the role of a-tocopherol as the most effective antioxidant in foods, which it confidently is in vivo. There are scarce data on antioxidant activity of tocotrienols. Tocotrienols are as efficient as tocopherols in quenching peroxyl radicals in solutions (Packer, 1995), whereas in membranes, tocotrienols seem to be more active (Packer, 1995 Qureshi et al., 2000). Depending on the environment and conditions, a-tocopherol may act as a better or a worse antioxidant than the other vitamers. 

Functional Foods Biochemical and Processing Aspects, Volume 2 

Other tocopherols and tocotrienols have not been shown to act as prooxidants. For example, antioxidant activity of 8-tocopherol increased parallel to concentration up to 2000 pg/g in a simple oil model (Huang et al., 1995). Adding tocopherols as mixtures is an efficient means to improve oxidative stability of oils (Parkhurst et al., 1968 Huang et al., 1995), because in mixtures, they protect and regenerate each other (Niki et al., 1986 Lampi et al., 1999). Thus, addition of y- or other tocopherols and tocotrienols together with a-tocopherol may enhance the antioxidant activity of a-tocopherol. 

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Shahidi, F., Wanasundra, U., and Amarowicz, R. 1995. Isolation and partial characterization of oilseed phenolics and evaluation of their antioxidant activity. In Food Flavors Generation, Analysis and Process Infleunce (G. Charalambous, ed.), Elsevier Science. 

Roginsky, V. and Lissi, E. (2005) Review of methods to determine chain-breaking antioxidant activity in food. Food Chem., 92,235-254. 

TABLE 29,1 Results of Antioxidant Activity in Foods by Several Types of Measures... 

Betalains have shown strong antioxidant activities in biological environments such as membranes and LDLs," -" suggesting that the consumption of betalain-colored foods may exert protective effects against certain oxidative stress-related diseases (i.e., cancers) in humans. Beetroot has been used as a treatment for cancer in Europe for several centuries. The high content of betanin in red beetroot (300 to 600 mg/kg) may be the explanation for the purported cancer chemopreventive effects of beets. 

Netzel, M. et al., Sources of antioxidant activity in Australian native fruits. Identification and quantification of anthocyanins, J. Agric. Food Chem. 54, 9820, 2006. 

Wang, S.Y. and Lin, H.S., Antioxidant activity in fruits and leaves of blackberry, raspberry, and strawberry varies with cultivar and developmental stage, J. Agric. Food Chem., 48, 140, 2000. 

Mezadri T, Villano D, Fernandez-Pachon MS, Garcia-Parrilla MC and Troncoso AM. 2008. Antioxidant compounds and antioxidant activity in acerola (Malpighia emarginata DC.) fruits and derivatives. J Food Comp Anal 21(4) 282-290. 

The thiocyanate method involves measurement of the peroxide value using linoleic acid as substrate and has also been widely used to measure the antioxidant activity in plant-based foods such as ginger extracts (Kikuzaki and Nakatani 1993), fruit peels (Larrauri and others 1996 1997), extracts from vegetable by-products (Larrosa and others 2002 Llorach and others 2003 Abas and others 2006 Peschel and others 2006), blueberry juice, wines, and vinegars (Su and Chien 2007). 

Many methods are available for determining food antioxidant capacity, which is an important topic in food and nutrition research. However, there is a great need to standardize these methods because the frequent lack of an actual substrate in the procedure, the system composition, and the method of inducing oxidation could limit their accuracy. In fact, antioxidant activities in complex systems cannot be evaluated satisfactorily using a single test, and several test procedures may be required. The search for more specific assays that can be more directly related to oxidative deterioration of foods and biological systems should be the objective of future investigations. 

Cano A and Arnao MB. 2005. Hydrophilic and lipophilic antioxidant activity in different leaves of three lettuce varieties. In J Food Prop 8(3) 521—528. 

Cho YS, Yeum KJ, Chen CY, Beretta G, Tang G, Krinsky NI, Yoon S, Lee-Kim YC, Blumberg JB and Russell RM. 2007. Phytonutrients affecting hydrophilic and lipophilic antioxidant activities in fruits, vegetables and legumes. J Sci Food Agric 87(6) 1096-1107. 

Deepa N, Kaura C, Singh B and Kapoor, HC. 2006. Antioxidant activity in some red sweet pepper cultivars. J Food Compos Anal 19(6-7) 572-578. 

Di Majo D, Giammanco M, La Guardia M, Tripoli E, Giammanco S and Finotti E. 2005. Flavanones in citrus fruit structure-antioxidant activity relationships. Food Res Int 38(10) 1161-1166. 

Heimler D, Isolani L, Vignolini P, Tombelli S and Romani A. 2007. Polyphenol content and antioxidative activity in some species of freshly consumed salads. J Agric Food Chem 55(5) 1724—1729. 

Jayaprakasha GK, Patil BS and Bhimanagouda S. 2007. In vitro evaluation of the antioxidant activities in fruit extracts from citron and blood orange. Food Chem 101 410-418. 

Martinez-Valverde I, Periago MJ, Provan G and Chesson A. 2002. Phenolic compunds, lycopene and antioxidant activity in commercial varieties of tomato (Lycopersicum esculentum). J Sci Food Agric 82(3) 323-330. 

Stewart RJ, Askew EW, McDonald CM, Metos J, Jackson WD, Balon TW and Prior RL. 2002. Antioxidant status of young children response to an antioxidant supplement. J Am Diet Assoc 102(11) 1652—1657. Stratil P, Klejdus B and Kuban V. 2006. Determination of total content of phenolic compounds and their antioxidant activity in vegetables evaluation of spectrophotometric methods. J Agric Food Chem... 

Frankel, E.N., Waterhouse, A.L., and Teissedre, P.L., Principal phenolic phytochemicals in selected California wines and their antioxidant activity in inhibiting oxidation of human low density lipoproteins, J. Agric. Food Chem., 43, 890, 1995. 

Olive fruit has long been used as a food and as a source of edible oil for frying and salad dressings. The phenolic content in olive fruits is known to contribute to the natural bitterness and the final color of fruits (66), and to provide natural antioxidant activity in olive oil... 

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