Comparison of antioxidant capacities of different types of tea using the spectroscopy methods and semi-empirical mathematical model

The antioxidant properties of different types of tea—green, black and earl grey—were investigated using the EPR spectroscopy method based on a new semi-empirical mathematical model and on a single EPR spectroscopy measurement. The obtained values of the antioxidant capacity were correlated with the bioactive ingredient content identified through the NMR spectroscopy. Moreover, an attempt was made to determine what impact on the antioxidant properties of tea does adding sugar, milk, lemon and honey have. All studied teas exhibited antioxidant properties. The best DPPH free radical scavengers were green teas. Adding sugar, milk and lemon juice to tea did not significantly impact the antioxidant properties of the infusion; adding honey, however, caused an increase in the total antioxidant capacity of the infusion. The aromatic proton content correlates positively with the antioxidant capacity value.