CHEMICAL DRIVERS OF POSITIVE REDUCTION IN NEW ZEALAND CHARDONNAY WINES

Abstract

According to winemakers, wine experts and sommeliers, aromas of wet stone, mineral, struck match and flint in white wines styles, such as those produced from Vitis vinifera L. cv. Chardonnay, are considered to be hallmarks of positive reduction.1,2 In recent years, the production of Chardonnay styles defined by aroma characteristics related to positive reduction has become more desirable among wine experts and consumers. The chemical basis of positive reduction is thought to originate from the concentration of specific volatile sulfur compounds (VSCs), including methanethiol (MeSH) imparting mineral and chalk notes,3 and benzenemethanethiol (BMT) responsible for struck match and flint.1,4 However, the role of other aroma compounds, including esters, higher alcohols, and other VSCs, and their contribution to the sensory perception of positive reduction in New Zealand (NZ) Chardonnay wines has not been fully investigated. We selected 12 commercial NZ Chardonnay wines to represent a range of styles from low to high intensities of mineral and flint. Wine aroma profiles were analysed using headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Quantitative descriptive analysis (QDA) was performed on the same wines using a trained panel. Wines varied greatly in both their chemical and sensorial characteristics. Multivariate analysis showed that there were several key VSCs found to be explanatory variables driving the perception of attributes related to positive reduction in the NZ Chardonnay wines. These results will be presented in the context of winemaking techniques that can be applied by the industry to achieve Chardonnay styles with positive reduction, if desired by the winemaker.