Project 3.1.1

Identification and control of volatile compounds responsible for important sensory attributes

Project summary

The flavour of wine is determined to a large extent by volatile compounds that are perceived during consumption by the sense of smell. The overall flavour of a wine, as well as specific flavour notes, is provided by dozens of naturally occurring chemical compounds of widely varying potency and concentration.

Within this project, the formation of, and factors which influence aroma compounds recently found to be responsible for ‘stone fruit’ (apricot-peach), which is common in Chardonnay and other white varieties, will be investigated, with fermentation and vineyard studies and analyses of commercially produced wines.

The role of the capsicum-like methoxypyrazine compounds in Shiraz wines, previously considered not relevant to green flavour in this variety, will be explored through whole bunch fermentation studies, analysis of stalks and leaves, and determination of the genetic basis of the expression and regulation of this metabolite in grape bunches through collaborative work with CSIRO.

Jammy/raisin flavour will be studied in collaboration with Project 4.1.1 (Managing the impact of vintage advancement and compression). The identity of the compound(s) that give overripe jammy/raisin flavour of Shiraz, and more generally the effect of bunch exposure, have not been adequately established. The lack of knowledge of the compound(s) responsible for this flavour is a major gap in setting a measurable target in viticultural projects, especially given increases in growing season temperatures and vintage compression. The effect of bunch exposure on this and other flavour compounds, including TDN which contributes bottle-aged character to Riesling wines, will also be examined in this project.

The role of thiols and other sulfur compounds in red varieties will be determined. Foliar nitrogen and sulfur vineyard sprays have been shown to have the potential to positively affect thiol concentrations in wine, and will be investigated.

Working with the rotundone mapping Project 4.4.4, the compound causing ‘musk’ and (non-pepper) spice in Shiraz will be investigated. In addition, investigations of Shiraz wines sourced from the rotundone (4.4.4) and terroir projects (3.3.1, 4.4.1) will allow determination of new or less understood volatiles that are key to premium wine flavour.

The effect of blending alternative grape varieties with established varieties produced in the Riverina, Riverland and Murray Valley regions will be investigated, to provide enhanced flavour characteristics, acid, colour, and weight to these types of wines. The project will also have a component whereby off-flavours and taints will be identified and studied.

Current practice in sensory evaluation of research wines uses sensory descriptive analysis, and while considered the most powerful and sophisticated method available, requires several weeks of data generation and substantial time for data analysis. In recent years, alternative faster methods have been developed in food science applications. This project will evaluate these protocols to determine their utility in wine studies and for wider industry use. Advantages of using untrained consumers compared to trained panellists will also be assessed. The project will also investigate technology for simulating wine experiences in lifelike environments, to better capture consumer responses.