WINETECH Technical Yearbook 2021

OENOLOGY RESEARCH | MARCH 2021

The effect of a reductive aroma compound on the perception of fruity volatile thiols CARIEN COETZEE 1 , SEBASTIAN VANNEVEL 2 , JEANNE BRAND 2 , ASTRID BUICA 2 & WESSEL DU TOIT 2 : 1 Basic Wine, Stellenbosch; 2 South African Grape and Wine Research Institute, Department of Viticulture and Oenology, Stellenbosch University, Stellenbosch KEYWORDS: Volatile thiols, reductive winemaking.

THE FRUITY VOLATILE THIOLS and the compounds associated with reductive aromas often occupy the same wine due to similar conditions supporting their formation and preservation. These two aroma groups contribute contrasting flavours and understanding the sensory interactive effects between the compounds can help in the management of reduction in wines. INTRODUCTION Protecting must and wine from oxygen and the generous use of antioxidants are considered to be reductive winemaking techniques. These techniques help to preserve many oxidation-sensitive wine constituents, including important aroma compounds. The fruity volatile thiols are potent aroma compounds and contribute to the sensory perception of tropical fruit flavours, such as guava, passion fruit and grapefruit. Protecting the volatile

thiols from oxidation (by maintaining a reductive environment during processing) is important to preserve the pleasant fruity aromas. However, reductive handling of wine can also result in the formation of unwanted aromas often simply referred to as “reductive” aroma. Like the volatile thiols, reductive compounds contain a sulphur atom, however, the aromatic attributes used to describe reductive aromas are usually unpleasant with descriptions such as rotten egg, vegetative and burnt rubber. The preservation of the volatile thiols (which are formed during fermentation) and the formation of reductive aromas thus occur under similar conditions: an oxygen-deprived environment usually in combinat ion wi th ant ioxidants , such as sulphur dioxide and ascorbic acid. Consequently, both aroma groups (fruity volatile thiols and reductive

WINETECH TECHNICAL YEARBOOK 2021 | 64