UV-C-induced changes in a white wine: Evaluating the protective power of hydrolysable tannins and SO<sub>2</sub>

Abstract

UV‑C treatment is a non-thermal technology that could be used for the microbiological stabilisation of must and wine. However, light - in this case UV‑C light - has an impact on wine. UV‑C is a high-energy light source and can promote photo-induced oxidation reactions. The formation of reactive oxygen species during the UV-C treatment of wine can be prevented via supplementation with antioxidants. These have the ability to neutralise reactive oxygen species or directly interact with the products of photo-induced oxidation reactions. This study investigates the impact of different UV‑C doses on the chemical and sensory characteristics of Chardonnay wine and examines the protective effect of two antioxidants: sulphur dioxide (SO2) and hydrolysable tannins. A sensory evaluation revealed that UV‑C doses higher than 1 kJ/l increased the colour intensity and the oxidised and burnt odour attributes of the wine. The peach odour attribute decreased with UV‑C treatment. On a chemical level, increasing UV‑C doses promoted the formation of compounds such as acetaldehyde and 2‑aminoacetophenone (2‑AAP), while causing the degradation of C13‑norisoprenoids, higher alcohols, monoterpenes and esters. Contrary to expectations, SO2 did not act as an antioxidant when wine was treated with UV-C. It intensified the burnt odour attribute and did not mitigate the intensity of the oxidised odour attribute, which can be explained by the formation of acetaldehyde. However, hydrolysable tannins acted as antioxidants when combined with UV‑C treatment, effectively mitigating the formation of 2‑AAP and acetaldehyde, while preventing the wine from becoming oxidised.