Solvent effects on total antioxidant capacity of foods measured by direct QUENCHER procedure

This study aimed to investigate the effects of solvent composition of different radicals (ABTS, DPPH) on measured total antioxidant capacity (TAC) of foods determined by the QUENCHER procedure. The working solutions of ABTS radical were prepared in the mixture of water–ethanol with different volume ratios (0:100, 25:75, 50:50, 75:25, 100:0). The solvent composition had a significant effect on the measured antioxidant capacity of various food matrices including cereals, fruits and vegetables, pulses and nuts (p < 0.05). The use of ethanol alone gave the lowest values during measurement while introducing water to ethanol significantly improved the levels of antioxidant capacity. These results suggested that the mixture of water–ethanol (50:50, v/v) may be the most appropriate solution for standardizing the TAC database of foods tested by the QUENCHER procedure. The need of water is due to its ability to open the structure enabling better access of radicals to functional ends of the food matrices.