Project 5.3.1

Tracking trends in Australian wine composition and vineyard and winery practices

Project summary

This project will track trends in Australian wine composition and vineyard and winery practices. Compositional trends will principally be monitored by collating analytical data from wines submitted to the AWRI’s analytical laboratories for commercial analysis; thereby extracting substantial value from an existing sample set consisting of more than 25,000 samples analysed annually, at a cost of considerably more than a million dollars. If necessary, that existing data set will be augmented with supplementary samples and analyses to address identified gaps (for example, in relation to specific regions, wine types or analytes), or through the addition of other data sets (such as Wine Australia’s export certificate data).

Trends in production practices will principally be monitored via a web-based survey of vineyard and winery practices performed at approximately five-yearly intervals, supplemented by visits to a range of producers and industry bodies, to consult and gain additional perspectives on the compiled data. These surveys will be equivalent to the AWRI Vineyard and Winery Practices Survey performed in 2016, which is to be published in 2018.

Latest information

The compositional and practices information, together with interpretative commentary, will be collated in a report to be distributed to levy payers on an approximately five-yearly cycle (aligning with the conduct of each practices survey), via a range of extension mechanisms such as industry and academic journals, AWRI roadshows, and presentations in various other industry forums. This will be complemented by annual reports featuring only compositional data and likely to focus upon specific parameters of interest from year to year, primarily to be published in industry journals. This compositional information will further inform and feature in the AWRI’s extension activities and provide additional context to information generated by other sources, such as vintage trends identified by the AWRI helpdesk.

AWRI Vineyard and Winery Practices Survey
In late 2016, the AWRI performed a large survey (691 responses) of Australian vineyard and winery practices. A presentation was made to the 2017 ASVO viticulture seminar, where it formed the basis for a panel discussion on topics including the use of destemming harvesters, recycle sprayers and precision viticulture. Presentations were also made to the 2017 Crush Symposium, to the 2018 Winery Engineering Association conference and as part of regional tasting sessions on red wine production techniques. Among many other findings, the survey emphasised the importance of cross-flow filtration and the increased adoption of flotation for juice clarification in the Australian wine industry. It also showed that carboxymethyl cellulose has only been adopted to a limited extent for cold stabilisation, with chilling being by far the dominant technique. Slides from the presentations given are available for download and the full survey report will be issued by the end of 2018.

Brettanomyces survey
The AWRI helpdesk has observed an increase in the number of queries about Brettanomyces yeast every year for the last five years. There was interest in finding out if this trend was translating to an increase in 4-ethylphenol (4EP, the main aroma marker compound for this spoilage yeast) in Australian wines and if it might be linked to increased SO2 tolerance of strains currently being investigated in the research group. As such, a decision was made to revisit the Brettanomyces survey conducted by the AWRI in the 2000s. The original survey included commercially available bottled Cabernet Sauvignon wines from five regions across Australia over seven vintages, finishing with the 2005 vintage. That survey isolated and characterised any Brettanomyces sp. yeast present in the bottled wine and measured marker compounds including 4EP. The current update to the survey examined 91 wines from the 2015 vintage, from the same regions, providing a snapshot of the situation ten years later.

The mean concentration of 4EP in the 2015 wines tested was just 29 µg/L, even lower than levels reported in 2005 (Figure 18). The highest 4EP observed was 327 µg/L, which is below the sensory aroma threshold. Approximately 60% of the Australian wines tested contained ‘not detectable’ levels of 4EP. No viable Brettanomyces yeasts were isolated from any of the wines. These results suggest that the increased helpdesk queries regarding Brettanomyces are not correlated with a higher mean 4EP concentration in bottled Australian wine. The increased query numbers could be linked to enquiries about new monitoring techniques or treatment options that have been adopted over the last five years, rather than any increased incidence of spoilage. While current research on Brettanomyces (presented elsewhere in this report) has provided some evidence of increased SO2 tolerance of strains in some wineries, the survey results suggest that these strains are not yet having a widespread impact in Australian wineries, or that cases of viable Brettanomyces yeast are being treated more quickly and effectively during winemaking before production of 4EP, or that any badly affected wine is being identified earlier and not reaching the marketplace.

Project Contacts

Simon Nordestgaard
Eric Wilkes

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