An EPR study on tea: identification of paramagnetic species, effect of heat and sweeteners.
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 Mn(2+) and Fe(3+) 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 degrees C and the semiquinone radical lives up to 140 degrees C while Mn(2+) sextet disappears just above 100 degrees C in tea extract. Natural and synthetics sweeteners have different effects on the paramagnetic centers. White sugar (sucrose) quenches the Mn(2+) and semiquinone lines in black tea EPR spectrum, and glucose, fructose, lactose and maltose quench Fe(3+) line while synthetic sweeteners acesulfam potassium, aspartame and sodium saccharine do not have any effect on paramagnetic species in tea.
Biyik
Recep
R
Ondokuz Mayis University, Faculty of Art and Sciences, Department of Physics, 55139 Samsun, Turkey. recep.biyik@taek.gov.tr
Tapramaz
Recep
R
D028241:Camellia sinensis / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005290:Ferric Compounds / Q000737:chemistry; D006358:Hot Temperature; D017616:Magnesium Compounds / Q000737:chemistry; D013549:Sweetening Agents / Q000737:chemistry; D013662:Tea / Q000737:chemistry*
D005290:Ferric Compounds; D017616:Magnesium Compounds; D013549:Sweetening Agents; D013662:Tea