Developing objective measures of quality for sparkling wine

Building and measuring the quality of fine Australian sparkling wines, through identification of the impact compounds responsible for 'autolytic character' in sparkling wine, and novel winemaking technologies to hasten autolysis

Funding: Wine Australia

In-kind support: TIA, Central Science Laboratory, Hill-Smith Family Vineyards, Apogee Wines Tasmania and Josef Chromy Wines

Collaborators: WineTQ, University of Adelaide and the Australian Wine Research Institute

Total funding: $1.43 million

The compounds that impact upon quality in white and sparkling wines are poorly defined, if at all.

Dr Fiona Kerslake is leading a four-year research project to analyse impact compounds that contribute to the flavour, mouthfeel and textural properties of premium sparkling wine character.

As part of the process for making sparkling wine, the wine is left in contact with the lees (the sediment of dead yeast cells) after fermentation to age.

This process, called autolysis, is believed to be a vital component in shaping the flavours and mouth feel of premium wines by imparting a creaminess and reducing astringency.

The practice dates back to Roman times and in France, there are strict regulations for how long Champagne must remain in the autolysis stage from 15 months to three years, with some wineries leaving wine in autolysis for seven years.

However, an expert tasting of sparkling wines in 2010 revealed that sensory cues for 'autolytic character' were not clearly distinguishable nor agreed upon from 'aged wine' and industry is now questioning whether this 'autolytic character' is entirely attributable to yeast lysis or if some of this character is simply aged wine character.

Long ageing on lees delays the release of sparkling wines, adding significant cost to the producer.

Dr Kerslake's research will look at whether the long ageing in lees is responsible for producing the 'autolytic character' in aged wines.

If autolysis is not the mechanism for this character, then alternative processes may be available to streamline winery efficiency.

Novel methods that have been developed and applied by TIA in red wine maceration include ultrasound, microwave and endogenous enzymes and these methods are proposed to hasten yeast lysis.

The lengthy aging on lees period for premium sparkling wines makes research into this product a long-term investment, however this project will have the significant advantage of being able to access a set of research wines that have been en tirage for five years.

Analysis of volatiles and non-volatiles, in conjunction with objective measures of quality (BevScan, UV-vis spectral phenolic fingerprinting) and an expert tasting panel will not only contribute to initial impact compound identification of aged sparkling wines, but also provide final information as to the effect of the viticultural practices trial from which these wines were derived (Phase 1).

Phase 2 will investigate whether it is the ageing in lees that produces the autolytic character or simply the ageing of the wine itself that is responsible for the development of aged wine character and also whether novel technologies could hasten yeast lysis and contribute to the identification of impact compounds.

A UV-Vis spectral phenolic fingerprint (SPF) measure has been shown to discriminate juice and base wines based on viticultural practices and this will be validated for sparkling wines (Phase 1), used as a basis for in-line sensing of juice quality and will be compared to currently available conductivity meters (Phase 3) and for discriminating the provenance of juice (Phase 4).

The project also has strong industry support from Hill-Smith Family Vineyards, Apogee Wines Tasmania and Josef Chromy Wines.