An easy and fast test to compare total free radical scavenger capacity of foodstuffs

An easy and fast test has been designed to compare the total free radical s cavenging capacity (RSC) of various food samples. Black and green teas from different countries, and wines of different brands were studied and compar ed as examples of coloured liquids (water- and methanol-soluble); oils from different sources were used as examples of lipidic foodstuffs; apples of d ifferent varieties and spinach were analysed as solid foods. Dilutions of e xtracts of the described foodstuffs were prepared and aliquots of each dilu tion were spotted onto TLC silica gel layers in the form of a dot-blot test : layers were stained with a methanolic solution of the 2,2-diphenyl-1-picr ylhydrazyl radical. Dots of extracts of foodstuffs with RSC turned yellow, with a colour intensity depending on the RSC compounds present in the dilut ions. After Ih staining, the intensity of the yellow colour was measured wi th a chromameter (b* parameter) at one of the dilutions at which the colour value was linearly correlated to the concentration of the sample, Accordin g to these readings the different samples were organised in decreasing orde r of b* values, an order which corresponded to the decreasing order of RSC as determined by spectrophotometric methods. The dot-blot test was sensitiv e enough to detect differences of RSC between varieties and brands of water - or methanol-soluble products, but was not adequate for lipid-based compou nds. The test was also able to follow the variation of RSC during food proc essing as in, for example, the heat-treatment of spinach. Copyright (C) 200 0 John Wiley & Sons, Ltd.