21 February 2008 Does less mean more when it comes to wine quality?

Removal of leaves from grapevines during fruit ripening is a common management practice in New Zealand vineyards.

Aimed to increase light exposure on the grapes and reduce the incidence of disease, removing leaves is also thought to have a positive effect on the quality of wine from these grapes by increasing anthocyanins, the sugar: acid ratio, and tannin, as well as changing aroma compounds.

Pinot noir is an increasingly popular grape grown throughout New Zealand, and particularly in Canterbury.  Over the years viticulturists have worked with winemakers to improve the quality of Pinot noir and the increasing sales reflect the growing acceptance by consumers.

Scientists from the Food and Wine Group at Lincoln University have joined forces with Pegasus Bay Vineyard at Waipara to study the effects of leaf removal on the quality of Pinot noir wines.

“Pinot noir is now the second most widely planted grape in New Zealand so it is important that we do this research in order to design management techniques which are specific for the actual growing conditions here,” said Dr Roland Harrison who leads the project.

Belinda Kemp, who was previously a winemaker from the prestigious Nyetimber Vineyard in the UK, has come to New Zealand to answer this and other questions, as part of her PhD project into the effect of leaf removal on the quality of Pinot noir wines.

“A very exciting part of my work is the opportunity to characterise the composition of the wine tannins and identify the key ‘fruity’ and ‘green’ tannins of Pinot noir wines,” said Belinda.

This project involves her carrying out three leaf removal treatments and a control (no leaves removed) at different times after flowering in order to study the effect on tannin levels and composition in the resulting wines – using the microvinification techniques of small-scale winemaking.

The wine will be analysed chemically as well as by sensory evaluation (wine tasting) to ascertain whether there is a relationship between the timing of leaf removal and the composition and levels of tannins and aroma compounds.

Marie Debeauchesne, an exchange student from France, has been assisting with part of the project. She measured the levels of total tannins in a number of different red wines. Students from the Bachelor of Viticulture and Oenology degree were also able to familiarise themselves with the method as part of their laboratory classes.

This is a very hands-on project where Belinda is responsible for taking all the vineyard measurements on a structured time schedule that sees her regularly driving up to Pegasus Bay Winery during  the summer, before she even starts on making the wine after harvest. 

“This is a huge project and I am grateful for the help of the Pegasus Bay staff and my fellow students in taking the masses of measurements in the vineyard.”

Belinda’s research is funded by Pegasus Bay Winery, Nyetimber Ltd and New Zealand Winegrowers.

The project will run over three years and the first results will be available later this year.

FOR FURTHER INFORMATION CONTACT

Janette Busch
Lincoln University
Tel: +64 3 325 2811 
Email: buschj@lincoln.ac.nz