Project 4.1.1

Managing the impact of vintage advancement and compression

Project summary

Vintage compression places significant stress on harvest and processing logistics and capacity. However, the contribution to this phenomenon of management practices (e.g. improved irrigation or pruning), has not been separated from the effect of higher temperatures. In addition, trends in fruit maturity parameters other than sugar accumulation need to be investigated, as does the balance between titratable acidity (TA) and pH with sugar concentration. A better understanding of these trends will corroborate their likely relevance in future vintages, and inform both winery and vineyard management decisions.

Another important symptom of vintage compression, is delays in harvesting fruit and resulting high sugar/alcohol concentrations. Increases in grape sugar concentrations can be driven by the import of sugar from the vine, or by berry dehydration. Dehydration also results in a loss in yield, with a significant impact on vineyard profitability. A better understanding of the dynamics of sugar accumulation and aroma-relevant grape compositional changes, may aid harvest decisions and inform appropriate compensation for delays in picking fruit.

Another option to manage vintage compression is to increase the speed at which fruit can be processed. For red wines the major processing bottleneck is red fermenter capacity. Faster extraction techniques (including thermovinification and flash détente) can reduce the time that red ferments need to be in contact with skins. Unfortunately, these techniques can produce undesirable or non-traditional flavour profiles, which may make their adoption less attractive to industry. A range of extraction processing options will be investigated for red grapes on a commercial scale, to target more desirable and familiar colour, texture, and flavour outcomes.

The research plan includes:
• an extension of the analysis of the maturity dataset from Treasury Wine Estates for TA and pH, in order to track changes in these parameters (and their balance with sugar) from the late 1990s
• an evaluation of models for assessing the likely impact of climate change on TA and pH (and their balance with sugar)
• data analysis across a range of research data sets (already collected) of sugar accumulation and berry weight, to separate the impact of sugar importation vs berry dehydration
• characterisation of the impact of the amount, timing and methods of water addition on wine composition and style.

Additional chemistry and sensory support will be provided from Projects 3.1.1 (volatile aroma compounds) and 3.1.4 (managing wine extraction).