This project aims to assess differences between two premium quality grades of Shiraz fruit and establish chemical and spectral indicators which define premium quality in vineyards.
Secondary objectives are to identify vineyard or winery management options for changing grades and for reducing the cost of producing higher quality grapes.
The consistent production of premium grapes is often hindered by the inability to predict variability between and within vineyards, on both a regional and seasonal basis.
In order to accurately grade grapes destined for winemaking within the premium category, a greater understanding of the relationship between grape composition and wine style is needed.
The AWR 1202 project Assessment of relationships between grape chemical composition and grape allocation grade has identified a suite of analytical parameters for Shiraz grapes that are useful for predicting commercial grade, identifying non volatiles (phenolics, amino acids) as the most important factors for Shiraz.
This study will determine whether a significant difference exists between quality grades and seeks to understand the viticultural factors that underpin any identified differences.
Guidelines will be provided for the evaluation of grape quality, and will highlight vineyard and winery management strategies to increase the value of grapes, or reduce the costs of production.
Vineyards will be identified for each quality grade, primarily in the premium Barossa region, but also including the Limestone Coast, Langhorne Creek and McLaren Vale.
Samples will be taken to provide an assessment of vineyard heterogeneity and allow representative samples to be obtained for grading.
Fruit will be fermented according to commercial procedures and oak treatment will be applied to the wines in a standard format.
A range of chemical analyses will be performed on the grapes as well as a comprehensive phenolic profile using targeted analysis. The wines will be assessed sensorially to determine differences in quality and style.
A more accurate assessment of grape quality (objective measures) and understanding its spatial, viticultural and regional limitations will guide understanding of how vineyards can be better managed.
This will assist in the definition of new viticultural projects which emphasise sustainable practices and inform current management practices to produce grapes to specification.