Natural antioxidants as food and beverage ingredients - Natural Food Additives, Ingredients and Flavourings - page 111

Fig. 5.6 Polar compounds isolated from oregano.

et al. 2002), lamb (Simitzis et al. 2008) and turkey (Govaris et al. 2004), post
mortem.

Tea ( Thea sinensis L. )
Tea is one of the most consumed beverages across the globe and many ancient and
modern cultures tout its health benefi ts. There is much research going on regarding
the biological potential of tea and tea ingredients. Tea extracts have shown good
potential for stabilizing foods against lipid oxidation, resulting in an increase in
commercial interest. The antioxidant power of tea is highly correlated to its
phenolic content (Benzie and Szeto 1999). It is commonly recognized that the main
active phenolics in fresh tea leaves are polyphenols, known as catechins, which
become enzymatically oxidized during fermentation to yield the dark compounds
in tea: theafl avins and thearubigens. Epicatechin (EC), epicatechin gallate (ECG),
epigallocatechin (EGC), epigallocatechin gallate (EGCG - the predominant
catechin in green tea), theafl avin (TF), theafl avin monogallate A (TH-1A),
theafl avin monogallate B (TH-1B) and theafl avin digallate (TH-2) are the major
catechins and theafl avins. Thearubigens are not yet fully characterized and studied
(Ho et al. 1997) (Fig. 5.7 and Fig. 5.8). Just like most phenolics, the main mode
action results from oxygen-centered free radical scavenging (Yen et al. 1997).
It has also been suggested that metal chelation (Gramza and Korczak 2005)
and lipoxygenase enzyme inhibition (Xie et al. 1993) may play a role. In food
applications, tea catechins were found to reduce the thiobarbituric acid reactive
substance (TBARS) values in various meats and tissues (chicken meat, liver and
heart) if the chickens were supplemented with tea catechins (40% EGCG, 24%

￿ ￿ ￿ ￿ ￿