Investigating Soil, Juice and Wine Chemical Differences in Sauvignon blanc from Hawke’s Bay and Marlborough

Abstract

This study assessed whether there are variations at different stages of the winemaking process of Sauvignon blanc between two New Zealand wine regions. The evolution of soil, juice and wine was assessed between Hawke’s Bay and Marlborough vineyards. A Vineyard Ecosystem (VE) data set of 144 soil samples provided a model over multiple years of soil elemental composition. Observations from this model were applied to study differences seen in a smaller scale study of the four vineyard sites from the two regions. Principal Component Analysis (PCA) was constructed from the soil compositions of 55 elements measured via ICP-MS. This showed correlations between soil samples and the regions of origin. The PCA plots showed evidence of clusters formed within the Hawke’s Bay samples, separated by geographical location. This clustering was not clear within the Marlborough samples. The four vineyard sites were also assessed for elemental composition. Marlborough V Block showed the most abundance of soil elements, resulting from rich alluvial soils. The four sites were superimposed onto the PCA plots, to explore which VE data set samples were similar when projected onto the same principal components. Similar clustering was found between the data sets due to the sites originating from the same geographical sub-regions. Pearson’s bivariate correlations were constructed to assess relationships between soil elements and wine aroma compounds. Few significant correlations were seen, where benzaldehyde and α-terpineol correlated often. Grape juices were analysed for maturity data, and thiol precursors analysed by LC-MS. Severe weather events diluted Brix levels. S-3-(hexan-1-ol)-glutathione (Glut-3MH) concentrations were higher than S-3-(hexan-1-ol)-L-cysteine (Cys-3MH), increased levels could be explained by Botrytis incidence. Juices were inoculated with Saccharomyces cerevisiae EC-1118 and control samples were treated with DMDC. GC-MS analysis quantified wine aroma compounds, where concentrations were mostly influenced by yeast inoculation or grape geographical origin. Varietal thiols 3MH and 3MHA were below detection limits for both Te Tua wines and the control wines for Kikowhero. Marlborough wines indicated the highest concentrations of thiols. Thiol results showed the most significant difference between the two regions, indicating a potential influence of geographical origin on the wines. Both Hawke’s Bay and Marlborough produced different styles of Sauvignon blanc.