Chemical Elemental Composition from Vineyard Soil to Wine in Hawke’s Bay and Marlborough, New Zealand
The main aim of this study was to determine the elemental composition of matrices comprising the soil to wine journey. Two different viticultural management practices, herbicide-applied ‘contemporary’ and non-herbicide-applied ‘future’, were compared. All samples originated from Marlborough and Hawke’s Bay, and regional differences were explored. This study involved samples from 2015 – 2021 and included within-season time points (bud-burst, véraison, and harvest). Sauvignon blanc, Pinot noir, and Merlot grape varieties were analysed for elemental composition, and a survey of 100 commercial Sauvignon blanc and Pinot noir wines was carried out. Inductively coupled plasma mass spectrometry (ICP-MS) analysis for all samples explored concentrations of 54 elements. Statistical analyses showed that region was the most significant factor influencing elemental composition differences in soils. Management regime was driving some differences, and seasonal differences in soil elemental composition were considered non-significant. An analytical method measuring the elemental composition of grapevine bark was optimised and validated. A digestion method of HNO₃ (1.5 mL), H₂O₂ (1.5 mL), and HCl (4.5 mL) with 15 minutes of microwave digestion proved to be the optimal conditions for ICP-MS sample preparation. The elemental composition, as determined by ICP-MS of soil, bark, leaves, juice, and wine, confirmed regional differences. Chemometrics analyses were performed on the correlations of the different stages in the soil-to-wine system. Elements Na, Ti, Ba, and Sr, were the most significant drivers in the matrix and regional separations. This research is an important study in exploring possible chemical fingerprints to identify potential indicators of geographical origin. Machine learning techniques produced a classification model to distinguish Pinot noir and Sauvignon blanc based on elemental composition. Research scale and commercial wines were used, and the commercial wines were considered the most accurate model. This information is valuable to the New Zealand wine industry as it provides meaningful patterns connecting the vineyard environment to the wine in the glass.
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