Sulphite‐corrected, non‐phenolic and phenolic antioxidant capacities of fruit wines profiled by differential Folin‐Ciocalteu assay

Abstract

SummaryThe Folin‐Ciocalteu reagent (FCR) assay is a reliable and robust, in vitro measure of antioxidant capacity (AOC) of foods but in winemaking its use has generally been confined to measuring total phenolics. However, the contributions of non‐phenolics and sulphites, and total AOC are also of interest for winemaking process control and human health functionality. Accordingly, we adapted the FCR assay and evaluated it with a range of wines made from grapes and other fruits, viz. peach, Chinese quince, blueberry, bayberry and red dragon fruit. The novel protocol avoided recognised interferences and revealed a wide variation among the wines in the contributions of phenolics, non‐phenolics and sulphites to their total AOC. Of the fruit‐derived antioxidants, phenolics accounted for 67.7–98.9% and non‐phenolics, 1.0–26.0% of the AOC, respectively. Direct reaction of sulphites with FCR accounted for 0.1–10.6% of the AOC.