Influence of soil geochemistry on the chemical and aroma profiles of Pinot noir wines

The aroma and flavour expression of wines has long been considered to be intimately linked to the climate, soil and further aspects of the physical environment, as reflected in the concept of terroir. The distinctive and varied aroma profiles of Pinot noir wines and their link with soil geochemistry is of particular interest in defining geographical wine styles. Three neighbouring Pinot noir sites in Bannockburn, Central Otago, were selected with similar viticultural management techniques, and with the same 10/5 Pinot noir clone, for microvinification trials. Differences in climate, slope, aspect and elevation were minimal across these sites, but detailed studies showed that the soils at these sites had substantial textural and geochemical differences. Vine trunk circumference measurements, used as an indicator of vigour, were also different at each site. Replicated grape samples were obtained across the vineyard sites, and a uniform microvinification protocol was employed to minimize variations arising from the winemaking procedure. Differences were seen in the content of wine tannins, polyphenols, colour and of aroma compounds by GC-MS. The depth of colour in wines from one of the sites was lower than for the other two sites, and the wines also exhibited lower concentrations of important aroma compounds belonging to the floral terpenes and fruit ester classes. Particular aroma and polyphenol profiles were also seen in the remaining two wines, which can be associated with differences in the soil geochemistry. The results suggest that the soil component of terroir influences vine growth and berry properties that are in turn reflected in wine flavour and aroma characteristics.