1. The impact of vintage, environmental and viticultural factors on grape and wine composition
Neil Scrimgeour 1, Catherine Kidman 2, Allen Jenkins 2, Wies Cynkar 1, Peter Godden 1, Eric Wilkes 1, Paul Smith 1 Sue Hodder 2, Paul Petrie 3
1 The Australian Wine Research Institute, PO Box 197, Glen Osmond (Adelaide) SA 5064, Australia
2 Wynns Coonawarra Estate, Memorial Drive, Coonawarra, SA 5263, Australia
3 Treasury Wine Estates, Sturt Highway, Nuriootpa, SA 5355
Corresponding author’s
Introduction
The AWRI, in conjunction with Wynns Coonawarra Estate, assessed the impact of vintage, soil type and clonal differences on the phenolic profiles of Cabernet Sauvignon grapes grown in the Coonawarra Region of South Australia over four separate vintages from 2009 to This study provided some insight into the relative importance of environmental factors, viticultural techniques and vintage variability on fruit quality.
Selection of soil and clone types
Five Cabernet Sauvignon clones: CW44, G9V3, Reynella, LC10 and SA125, grown in one Coonawarra vineyard with two soil types (Terra Rossa and Ground Water Rendzina) were chosen for the study. Comparable vineyard management practices were applied during the course of the trial.   
Method
Bunch samples (20 whole bunches per treatment) were collected during each vintage at:
Beginning of veraison (10 samples)
Pre-harvest – approx. four weeks prior (10 samples)                  
Harvest ( 10 samples)
At harvest, sub-samples of approximately 200 g berries were analysed for total anthocyanins, tannins, pH, total soluble solids (TSS), electrical conductivity, dry matter (% moisture) and macro- and micro-elements.
60kg parcels of fruit were processed using identical winemaking techniques at the Penfolds Magill Estate Winery, South Australia. The wines were analysed for total pigments, phenolics, tannins, micro- and macro elements to compare the phenolic profiles of the resultant wines. The wines were tasted at Wynns Coonawarra Estate each vintage after bottling.
Grape and wine composition
Grape tannin concentration (dm) at harvest was significantly lower in 2011 and significantly higher in 2012 (Table 1). Some differences between the same clones grown on Terra Rossa and Rendzina were observed, but there were no consistent effects due to soil type or clone on any grape parameter. Vintage effects dominated, with high moisture content and lower sugar levels, pH and tannin content in the grapes in 2011.
Wines from 2010 exhibited the highest levels of colour, phenolics and tannin, whilst levels were lowest in the 2011 wines. Comparatively high tannin levels were only achieved when high tannin levels were present in the grapes. High colour levels were only achieved when the grapes were high in anthocyanins AND tannins, due to the increased levels of pigmented tannins forming during the winemaking process. Wines made from fruit grown using Clone SA125 on Terra Rossa was consistently the most preferred across each of the four vintages.
The impact of vintage (weather)
The effects seen on grape and wine composition appear to be a direct consequence of the well above average growing season rainfall and lower average temperatures that were experienced during 2011 (Figure 2).
Figure 2: Average monthly temperatures and cumulative rainfall in the Coonawarra across
The impact of the average temperature recorded in 2010 and 2012 can be seen in the high sugar levels and high tannin levels attained at harvest. The differences between anthocyanin levels also appears to be affected by the average temperatures recorded during the growing season, but the relationship in this instance appears to be inverse.
Table1: Grape and wine colour and tannin data across vintages for SA125, LC10 and Reynella clones grown on Terra Rossa soil. Suffixes indicate significant differences between average values for treatments, based on ANOVA.
Monitoring grape maturity to achieve targeted outcomes
Tannin levels decreased at a similar rate across the four vintages (Figure 1). Lower tannin levels were recorded at veraison in 2011, corresponding to lower tannin levels at harvest. Anthocyanin levels appeared to still be increasing at harvest in 2009 and In contrast, colour levels seemed to plateau in 2010 and 2012 at around Brix and approximately 15 days and 28 days before harvest, respectively.
Figure 1: Grape tannin and anthocyanin levels (measured on a dry matter basis) across vintages for SA125, LC10 and Reynella clones grown on Terra Rossa soil (dbh indicates days before harvest)
Measurement of tannin concentration at 3-4 weeks before harvest provided a good indication of tannin concentration to be expected in the fruit at harvest time and could be used to optimise picking times to achieve a desired target tannin level in the grapes.
Conclusion
Vintage conditions, especially average temperature, have the potential to affect tannin and colour levels in grapes. In this study, warmer vintages produced fruit with higher tannin levels and lower anthocyanin levels. An awareness of this can allow viticulturists and winemakers to make the most of ideal vintages, and minimise the impact of poor vintages through proactive management techniques in both the vineyard and the winery