Antioxidant activity assessment in fruit liquors and spirits: methods comparison

During the last few years, Portugal has seen an increasing trend in the development of new fruit-based products, such as liquors and spirits. The antioxidant capacity of fruit liquors and spirits, sourced commercially or produced on a pilot-scale, was assessed using two simple spectrophotometric methods: the 2,2’-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays. The major goal of this work was to find which of the two methods is the most suitable and accurate in determining antioxidant capacity for fruit liquors and spirits. In addition, the total phenolic compounds of both kinds of alcoholic beverages were determined by Folin-Ciocalteau method. Despite the widespread use of DPPH assay for distilled drinks, a weak Spearman correlation coefficient (r = 0.023) between ABTS and DPPH methods in spirits were found, as well as, between DPPH values and total phenolic compounds content (r = 0.239). This work highlights the limitations of DPPH assay when used for analysis of samples with very low antioxidant capacity, as distilled spirits.