Total Antioxidant Capacity of Food and Beverages

Another important field of application concerns food and beverages, especially wine, juices, and tea (A2, A11, A17, B4, K12, V7, Yl). The antioxidant components of food include vitamin E (a-tocopherol), vitamin A (retinoids), vitamin C (ascorbic acid), and also fi-carotene (provitamin A), other carotenoids (of which more than 600 compounds have been identified), flavonoids, simple phenols, and glucobrasicins (H3). Unfortunately, the TAC value of a food is not informative on the bioavailability of its antioxidants. It has been estimated that polyphenols are normally present in blood plasma at concentrations of 0.2-2 //M (PI). However, it has been demonstrated that feeding rats a quercetin-augmented diet can increase their plasma levels of quercetin and its metabolites up to 10-100 //M (M27), and transient increases in the concentration of plant-derived phenolic compounds can take place after ingestion of food and beverages, which may affect blood plasma TAC (see later). 

Red wines have higher TAC than white wines. Red Chilean wines were found to have TAC of 25.1-33.3 mM, whereas TAC of white wines was 2.9-52 mM Trolox equivalents (C3). Other studies found TAC of 12-14 mM for Californian Pinot Noir, Rioja, and Bouzy Rouge, 16 mM for Australian Shiraz, and 23 mM 

Comparison of antioxidant activities of several seasonings used in Asian cooking revealed exceptionally high TAC activities of dark soy sauces (47-147 mM) (L21). TAC of 1 ml of the most effective dark soy sauce was equivalent to 10 ml of red wine. It was pointed out that when evaluating the TAC of commercial products, attention should be paid to the addition of preservatives by manufacturers to the seasonings tested. Sodium benzoate (a preservative added to several seasonings) does not react significantly with ABTS +, but the sulfite content of certain white wines may lead to an overestimation of their TAC (L21). 

Comparison of various oat fractions showed the following potency of TAC pearlings (2.89-8.58 TE/g) flour (1.00-3.54 TE/g) trichome (1.74 TE/g) = bran (1.02-1.62 TE/g) (H7). The antioxidant activity of rye extracts was significantly correlated with their total content of monomeric and dimeric hydroxycin-namates. These data suggest that rye products may be a source of dietary phenolic antioxidants that may have potential health effects (A13, E3). 

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