An EPR study on tea: Identification of paramagnetic species, effect of heat and sweeteners

作者：Biyik Recep^*; Tapramaz Recep

来源：Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy , 2009, 74(3): 767-770.

DOI：10.1016/j.saa.2009.08.014

• Tea
• EPR
• Catechin
• Metal complex
• Semiquinone
• Sweetener
• Antioxidant

Tea (Camellia Siensis) 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 semiquirione 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.

• 出版日期2009-10-15