Objective wine grape quality measurement and benchmarking

Abstract

Objective wine grape quality measurement and benchmarking

Summary

This report outlines the 2002 Vintage Progress of the Wine Grape Quality Measurement and Benchmarking Group. The group comprises a number of vineyards in the Bendigo, Gundagai and Swan Hill regions. The focus of the group is to research objective quality measurement techniques and benchmark quality parameters. To do this we measure different aspects of 1. Vineyard, 2. Berries and 3. Wine. By measuring different stages of wine production we have found key aspects to benchmark and measure quality.

Multiple sites within a vineplot are required for quality measurement due to vineplot variability. Our results appear to have achieved this by randomly choosing three sites x 40 vines, covering 120 vines per vineplot (management unit, usually 5-10Ha). A reduction in sampling sites within a vineplot will provide misleading information on the quality of fruit within that area. One bunch per vine, i.e. 120 bunches per block provided data that produced good quality correlations; therefore large sample sizes are essential for accuracy.

Assessing vineyards over the Bendigo, Gundagai and Swan Hill regions, our results show that the two most important objective measures are Shoot Periderm Development and Berry Size. These were the two most important factors relating to wine quality. Shiraz vines with good Lignification of Shoots and Small Berries were also those producing the highest quality of wine. These measures are likely to provide a great deal of information on the management of the vines over the season, including water management and the application of stress at appropriate times.

In our attempt to relate an objective berry measurement with wine quality we discovered some pleasing relationships. In particular the concentration of phenolic compounds and percentage of skin to berry weight was able to explain approximately 70% of the variation in our predictive model. We are very pleased with these results and feel that they are attributed to good sampling and analysis procedures used in the experiment.

Results and progress amongst the group has been very pleasing. Further research is required to follow up indications form this vintage. We are looking forward to consolidating our techniques and obtaining a data set that will enable an accurate objective assessment of wine grapes.