The effect of viticultural treatment on grape juice chemical composition

AIM: Viticultural management regimes influence the soil elemental profile of a vineyard, determining the microbial community distribution, insect life, and plant biochemistry and physiology [1]. The interactions among these grapevines, pests and microbes can influence the chemical composition of grapes and, therefore, the metabolites of the wines [2,3]. The wine industry is becoming more aware of the importance that the vineyard ecosystem plays in grape and wine production; in addition, there is a growing desire to use fewer synthetic chemicals to promote natural and diverse vineyard ecosystems. This study investigates the effect of two different viticultural management approaches on grape juice composition. Key metabolites in juice samples originating from grapes subjected to different viticultural treatments (Contemporary – use of synthetic herbicides and Future – no use of synthetic herbicides) were measured prior to alcoholic fermentation. METHODS: Key metabolites, including amino acids, C6 compounds, and thiol precursors, were quantified in this study using a combination of GC-MS and LC-MS/MS [4]. SPE was used to extract volatile C6-compounds from the juices before analysis [5,6]. Basic oenological parameters of the juice samples were also determined. Data analysis was carried out using the software R and MetaboAnalyst. RESULTS: Twenty-wight important metabolites in New Zealand Sauvignon blanc, Pinot noir and Merlot juice samples were detected and measured. From the results, PERMANOVA factors (Variety, Vintage, Region and Treatment) were found to be significant (p-value < 0.05). Although the factor Treatment was less than the role of the intrinsic factors Variety and Vintage, it is essential to highlight that approximately 4.1% of the variation found within the data set can be attributed to the implementation of the viticultural management regimes. CONCLUSIONS: In this study, the chemical profile of New Zealand grape juice from grapes grown under different vineyard management regimes was explored. The results confirmed that the difference in metabolite profiles between vineyard management regimes was small but detectable. This information is noteworthy and valuable for grape growers because of increasing concerns regarding the use of synthetic chemicals in agriculture and the shift towards improved sustainable horticultural practices. ACKNOWLEDGEMENTS: The authors wish to thank the Bragato Research Institute, New Zealand Winegrowers, and the Ministry of Business, Industry, and Employment (MBIE), for funding this work.

Authors: Jin Wang – University of Auckland, New Zealand,Bruno FEDRIZZI, University of Auckland Rebecca E. JELLEY, University of Auckland Farhana PINU, New Zealand Institute for Plant and Food Research Limited Emma SHERMAN, New Zealand Institute for Plant and Food Research Limited Damian MARTIN, New Zealand Institute for Plant and Food Research Limited Claire GROSE, New Zealand Institute for Plant and Food Research Limited

Email: jwan910@aucklanduni.ac.nz

Keywords: grape juice, viticultural treatments, amino acids, c6 compounds, thiol precursors

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