Building and measuring the quality of fine Australian sparkling wines, through identification of the impact compounds responsible for ‘autolytic character’ in sparkling wine

Abstract

This study investigated innovative practices across the entire production process for growing and making sparkling wine. 

Viticulture – we demonstrated impacts on yield, and chemical and sensory properties in aged sparkling wine, associated with pruning (spur, cane), crop load (10 nodes, 60 nodes) and leaf removal treatments. 

Pressing – a proof-of-concept prototype was developed to ‘read’ juice phenolic fingerprint in real-time at the press and automate press fraction cut off (tank switching), based on UV-Vis reflectance at 240 nm and 290 nm.

Tirage – yeast disruption techniques (microwave, ultrasound, enzyme) were applied to yeast for tirage, and these achieved ‘aged’ aroma in wines sooner than control yeast treatment. 

Cellaring – some of these wines were aged on lees, off lees and on lees at high temperature (25°C). This demonstrated that ‘autolytic’ character in wines could be achieved through chemical aging, in the absence of yeast. High temperature aging, however, was associated with poor foam stability. 

The wide scope of this study identified several avenues for further research, particularly related to impact compounds for sparkling winemaking that might underpin objective measurement of sparkling wine quality.

Summary

This project – 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 techniques to hasten autolysis – was conducted in four parts. The first utilised research wines sur lie from a prior project to explore the impact of viticultural practices on aged sparkling wines. The second part examined mechanisms related to sparking wine quality including ‘autolytic character’ and associated mouthfeel, texture, and aromas. The third part sought key discriminant factors of phenolics in grape juice at the pressing stage and developed a proof-of-concept prototype to measure phenolics in-line and in real-time. The fourth part tested if spectral techniques could be used for regional discrimination of juices destined for sparkling wine production. 

The Tasmanian Institute of Agriculture at the University of Tasmania led this project and drew on expertise from the Australian Wine Research Institute, the University of Melbourne and Wine TQ. Several private wine companies supported the research, with major contributions by Hill-Smith Family Vineyard and Josef Chromy Wines. Hill-Smith Family Vineyard generously donated base wines and the time of their team for the autolysis component of the project. Josef Chromy wines generously provided facilities for the larger disgorging at 12 months in the autolysis component and allowed the research team to install in-line sensors in their press to prototype real-time measurement of juice phenolics. There were numerous other supporting wine companies, predominantly through winemakers’ time for sensory appraisal of wines via expert tasting panels.