This project aims to define features of terroir that contribute to the distinctive pepper-like aroma derived from the potent sesquiterpene compound ‘rotundone’.
The project seeks to understand the differences in genetic and biophysical factors that may result in large differences in rotundone concentrations at harvest, and provide insights into how rotundone levels may be manipulated and managed.
Identified in 2007, rotundone is the grape-derived ‘peppery’ flavour and aroma compound that is highly sought after in certain cool climate Shiraz wine styles.
In a survey of rotundone levels in Australian wines, the highest concentrations were generally recorded in Shiraz produced from the Grampians and Pyrenees regions. The levels of rotundone recorded at the Mt Langi Old Block site were the highest recorded in Australia; this site has been termed Australia’s ‘peppicentre’.
The research has demonstrated that rotundone concentrations within this single vineyard are markedly spatially variable and that cooler veraison to harvest periods and a southerly aspect appear to favour rotundone accumulation.
More recently, the pattern of rotundone variation has been shown to be stable from year-to-year even with large variations in the mean annual rotundone concentration.
Building on collaborative research between the AWRI, CSIRO and Mount Langi Ghiran, this project will:
- Generate rotundone and α-guaiene maps for three Shiraz vineyards and characterise their variation in vine performance and the underlying land via EM38, elevation and vigour mapping
- Investigate potential genetic determinants for rotundone concentration in planting material
- Investigate the potential relationship between soil microbes and inherent spatial variation in rotundone concentration
- Investigate the kinetics of rotundone accumulation
- Investigate the influence of the light environment around a grape cluster and its role in the formation of rotundone from α-guaiene and the degradation of rotundone in berries
- Investigate relationships between entomological and vertebrate herbivore activity on the inherent spatial variation in rotundone.
Ultimately improving understanding of how provenance and terroir drive the expression of sought-after and highly valued wine styles will enhance the message of what makes Australian wines different and unique and will help elevate the status and consistency of supply for Australian fine wine in the international marketplace.