Investigating the phenolic composition of orange wines: studying the effects of oxidation and skin contact on white wine tannin

Abstract

An in-depth analysis of orange wines was conducted to assess factors affecting the phenolic composition. Orange wines were produced from Pinot Gris juice and table grape skins from September 2017 to March 2018. Factors included in this experiment were different ratios of skin contact to juice, additions of sulfur dioxide and aging. Basic wine data was analysed along with methylcellulose precipitable tannin, fractionation by solid-phase extraction and mean degree of polymerisation via acid catalysis in the presence of excess phloroglucinol. Increasing rates of skin addition resulted in a higher tannin composition in wine, along with an increase in pH and a decrease in TA and alcohol percentage. The use of SO2 limited tannin development, mean degree of polymerisation and affected the proportions observed in fractions two and three, but protected total phenolics from oxidation over time, especially those present in fraction one. The use of SO2 also resulted in orange wines with a lesser degree of browning. Orange wine phenolics develop in a similar way to red wine phenolics and are affected by similar winemaking conditions, however further study is required to confirm results.