Determination of thresholds for bunch rot contamination of grapes and techniques to ameliorate associated fungal taints

Summary

Objectives

This project aims to

  • develop spectral methods to discriminate bunch rots on grapes and estimate their levels
  • determine thresholds for acceptable levels of bunch rot in grapes, in terms of wine quality
  • explore the use of fining agents to reduce the quality impacts of making wine with bunch rot infected grapes.

Background

Wine made from bunch rot affected grapes can taste mouldy, earthy and musty. Because of this, fruit loads containing bunch rot affected grapes can be downgraded or even rejected at the winery. The amount of a particular bunch rot type that can be tolerated before there is a noticeable impact on wine quality is poorly defined and quantifying and differentiating bunch rot type in grape loads is difficult.

Research approach

This project will build on previous promising results showing that bunch rot type on grapes could be differentiated by spectral methods, specifically by ATR-FT-IR. These methods will be compared with others, using naturally and artificially infected whole bunches. Bunches infected with different amounts of rot will be made into wine and the level of taints will be followed during the winemaking process and after treatment with fining agents. Sensory testing will be performed and the data correlated with the analytical measurements and the different infection rates to determine thresholds for bunch rot tolerance.

Industry benefit

The knowledge and tools generated in this project will help grapegrowers and winemakers objectively assess the extent of bunch rot infection and support decision making regarding use of bunch rot infected grapes.