Elucidating the effects of environmental volatile compounds on red wine aroma and flavour, and evaluating the potential for novel cover crops in viticulture

Summary

Objective

The aims of this project are to determine the effects of surrounding vegetation on vineyards, and how they may affect grapes and wine through volatile compound adsorption. This can be achieved with the following objectives:

1. Conduct grapevine exposure experiments, using different nearby plants, to evaluate volatile impact.
2. Analyse the chemical profile (terpenoids, thiols and other compounds) of wines made after exposure testing, to determine the effects of volatile transfer.
3. Conduct sensory analysis of experimental wines, to evaluate consumer response. 
4. Assess suitability of novel cover crops (including industrial hemp and/or agave) in viticulture by:
   • Investigating agronomic factors e.g. soil chemical/structure, water use of crops, and/or pest/disease effects on vines.
   • Analysing vine yield, costs of novel cover crop implementation and benefits to environmental sustainability or vineyard income.

Background

Vegetation surrounding vineyards has been to affect wine aroma through the transmission of volatile compounds onto grapevines. This is exemplified by the effect Eucalyptus trees have on vineyards, where the transmission of 1,8-cineole (a volatile monoterprene) from the trees becomes adsorbed onto grapevines and gives resulting wines a distinct ‘eucalypt’ aroma at distances up to 50-100m. The environmental vegetation around vineyards is changing, for two main reasons.

Firstly, the emphasis on sustainable agricultural practices is increasing, leading to the planting of different crops that can provide various benefits to the health of an ecosystem, or exploration of mixed-use agriculture. For example, industrial hemp is gaining popularity, owing to its benefits to soil structure and chemistry, and biodiversity, while providing high rates of carbon sequestration, and generating a high value crop. These benefits are attractive to viticulturalists looking to improve vineyard health or as a potential second income source, if it could be used as a novel vineyard cover crop. These benefits are attractive to viticulturalists looking to improve vineyard health or as a potential second income source, if it could be used as a novel vineyard cover crop. In addition, other plantings for environmental protection (e.g. windbreaks or biodiversity improvements) are also becoming more common.

The second change in vegetation is a result of the changing climate, which is causing farmers to plant different crops to cope, and accelerates the spread of invasive weeds. These changes to vegetation could impact wine aroma, through the transfer of volatiles in the same manner as Eucalyptus trees, and affect grapevines – particularly if novel cover-crops are being explored, given their proximity to vines. A 2023 study in New Zealand investigating industrial hemp as a cover-crop with Sauvignon Blanc showed promising results in terms of soil chemistry/structure and grape yield, but did not consider wine quality. As with 1,8-cineole, the potential impact on wine aroma as a result of volatile compound transfer is of much more relevance to red wine, which is a distinct research gap.