New grape and wine chemistry research initiatives to bring long-term benefits to the Australian wine industry

Abstract

Significant progress has been made in a number of areas including the isolation, identification and characterisation of precursors to aroma compounds in grapes and wines, understanding the role of oxidative processes including precursors to the pepper compound, rotundone, developing non-destructive methods for the prediction of harvest date in the vineyard, understanding lees autolysis and the development of methods to synthesise phenolics, glucosides and aroma compounds.

Summary

The main objective was to facilitate the application into grape and wine research of the Project Supervisor’s more general synthetic organic chemistry background to undertake research of benefit to the wine industry attract chemistry graduates from their traditional research pathways into the wine chemistry field to complement the oenology/biochemistry graduate pool develop further research links to address Australia’s grape and wine research needs leverage further funding opportunities such as ARC LINKAGE partnerships and PhD scholarships. In terms of this latter aspect, leverage of the Wine Australia funds was successful; an LCMS instrument, GC’s, a microwave reactor, an MLCCC, HPLC and other general laboratory equipment was procured through the various university funding schemes by leveraging Wine Australia funds. The equipment is shared with other research groups conducting grape and wine research. The projects have been conducted primarily by PhD candidates with approximately 90% of the scholarships provided by the University of Adelaide or federal scholarship schemes rather than through this project. The main outcomes are: Further understanding of the role of hydrogen peroxide and ways to measure it in grape, vine tissues and wines. A non-destructive method for predicting berry harvest date in the vineyard utilising changes in peduncle colour was developed. A library of over 50 new potential biodegradable antifungals for botrytis control were synthesised and evaluated. Two new endoperoxides and one pyran compound showed promise when compared to iprodione. Further understanding of the role of reactive oxygen species in grapevine growth and wine production. A natural precursor to rotundone, (‘ pepper ‘) was tentatively identified. The role of peroxide and peroxide compounds in root development was examined with the model plant, Arabidopsis thaliana. A microwave treatment for autolysis of lees prior to back addition to wine was developed. This has the potential to shorten lees contact times from months or years to weeks. Sensory trials indicate there are differences between wines treated with normal lees and lees prepared by microwave treatment. Synthesis of ABA-like compounds and a preliminary understanding of how these compounds may influence plant responses relating to water retention and ripening. Identification of several new glycoside aroma precursors in Tempranillo and a glucoside of cinnamic acid hown to be precursor of ‘Brett’ taint. Further understanding of how the potent odorant, wine lactone (‘coconut’, ‘woody’, ‘sweet’), forms in wines and how to prepare the furanoid linalool oxides (‘floral’, ‘sweet’) for future research. Further understanding of the roles of glycoconjugated wine phenolics and the synthesis of phenolic glucosides and related structures. This facilitates their identification in wine which may aid in future research on these complex molecules in wine and how they contribute to texture, colour and mouth feel of wines.