An EPR study on tea: Identification of paramagnetic species, effect of heat and sweeteners
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Date
2009-10
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Publisher
Elsevier
Abstract
Tea (Camellia Sinensis) is the most widely consumed beverage in the world, and is known to be having
therapeutic, antioxidant and nutritional effects. Electron paramagnetic resonance (EPR) spectral studies
made on the tea cultivated along the shore of Black Sea, Turkey, show Mn2+ and Fe3+ centers in green tea
leaves and in black tea extract. Dry black tea flakes and dry extract show additional sharp line attributed
to semiquinone radical. The origins of the paramagnetic species in black tea are defined and discussed.
Effect of humidity and heat are investigated. It is observed that dry extract of black tea melts at 100 ◦C
and the semiquinone radical lives up to 140 ◦C while Mn2+ sextet disappears just above 100 ◦C in tea
extract. Natural and synthetics sweeteners have different effects on the paramagnetic centers. White
sugar (sucrose) quenches the Mn2+ and semiquinone lines in black tea EPR spectrum, and glucose, fructose,
lactose and maltose quench Fe3+ line while synthetic sweeteners acesulfam potassium, aspartame
and sodium saccharine do not have any effect on paramagnetic species in tea.
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Keywords
Tea, Çay, Catechin, Katekin, Sweetener, Tatlandırıcı, Antioxidant, Antioksidan, Semiquinone, Semikuinon, Metal complex, Metal kompleksi, EPR
Citation
Recep, B. ve Recep T. (2009). An EPR study on tea: Identification of paramagnetic species, effect
of heat and sweeteners. Spectrochimica Acta Part A : Molecular and Biomolecular Spectroscopy, 74 (2009), 767–770.