Objective measures of quality and provenance in Australian vineyards
This project builds on knowledge gained in Project AWR1202 which identified important chemical predictors for commercial grape quality grading. Based on this successful proof of principle study, there is interest from wine producers to further explore the potential of this approach, using commercial Shiraz vineyards.
This project will initially assess differences between two premium quality grades (Q2 and Q3) of Shiraz fruit and wine from 20 vineyards primarily within the Barossa Valley (with reference samples from other regions in SA). Fruit and wine will be sourced from industry partner, Pernod Ricard Winemakers (PRW), who have historically produced wines across a variety of quality grades, including ultra-premium. The aim is to establish chemical and spectral indicators which define Q2 and Q3 vineyards. Wines will be produced commercially from each vineyard and analysed compositionally and sensorially to determine differences in styles achievable. The primary output of the study will be the ability to determine the key chemical indicators associated with quality rating and wine style in premium Shiraz, and how they vary by quality grade and region. Secondary objectives are to identify vineyard or winery management options for shifting Q3 to Q2, and for reducing the cost of producing Q2 grapes.
From 2018, This project forms part of a new multi-agency collaboration to research Shiraz terroir across a range of scales, primarily in the Barossa Valley. At the sub-regional scale, 23 sites were monitored with fruit undergoing sampling for ripeness, yield assessment, chemical analysis and small-lot winemaking. These sub-regions were identified by the Barossa Grounds Project, and are classified as Northern Grounds, Central Grounds, Southern Grounds, Western Ridge, Eastern Ridge and the Eden Valley (Figure 15). The AWRI’s involvement in the project has been to perform multiple analyses of volatile and non-volatile compounds in the small-lot wines. In subsequent seasons, vineyard management interventions will be imposed on selected sites to determine the potential to optimise a site’s terroir. These management practices will aim to influence vine growth and development, and to establish a cause and effect for environmental impacts on fruit and
Understanding the chemical diversity of Shiraz wines from Barossa sub-regions
For the first year of the study (2018), three or four Shiraz vineyards were selected from each of the six sub-regions, and three zones were chosen within each vineyard. From the wines made from each site, multivariate models were built using chemical data to distinguish the characteristics of each sub-region. It was found that the models were not able to successfully differentiate among the Barossa sub-regions apart from the Eden Valley. The Eden Valley has a greater elevation, and is notably cooler and wetter than the rest of the Barossa Valley, with 1,390 heat degree days (vs 1,710) and 280 mm of rain (vs 160 mm) during the growing season. The Eden Valley wines were defined by high concentrations of minor grape anthocyanins (non-malvidin) as well as higher levels of flavonols. They also had higher levels of hexyl acetate, and markedly lower concentrations of β-damascenone than wines from the remaining sub-regions of the Barossa Valley. Since the important phenolic and volatile compounds identified are influenced by environmental conditions such as sun exposure, temperature and potentially elevation, additional data will be required to reveal if there are inter-seasonal trends.