Determining the quality of wine grapes from flavour and aroma analysis
The Food Futures Flagship has developed methods to characterise and classify the flavour and aroma of wine grapes.
10 January 2012 | Updated 11 January 2012
Food Futures Flagship researchers have worked with descriptive sensory panels of lay people and senior winemakers to discriminate subtle differences between Cabernet Sauvignon grapes sourced from different vineyards and the wines made from them.
The sensory panels functioned like a scientific instrument to determine key sensory differences among grape samples. The observations of the panels were backed up by measurements made with analytical instruments.
The researchers also used a commercially available ‘electronic nose’ to classify batches of Cabernet and Riesling grape juice according to their region or ripening stage. This provided insights into the development of wine flavour and established the groundwork for using electronic noses to assist in grape harvesting and wine production.
What we did
The researchers trained a group of lay people to measure the flavour and aroma of grape juices and the wines made from them. A team of wine-making experts made a second evaluation of the same berry and wine samples to provide insights from industry professionals.
Over three vintages, there was broad agreement between the groups. In blind tastings, both panels could differentiate the samples based on:
- geographical location of the source vineyard
- quality designation
- subtle variations within single vineyards giving rise to changes in grape characteristics.
The researchers followed up with a gas chromatography mass spectrometry olfactometry (GC-MS-O) assessment, in which complex mixtures of odours are separated and a panel of trained human assessors records the strength and character of the smell of each component identified by the instrument.
The researchers pinpointed important qualitative and quantitative differences in the volatile flavour patterns among Cabernet Sauvignon grapes from different vineyards. Finally, the researchers carried out comprehensive chemical analysis on all the grapes and wine samples.
The researchers want to develop rapid, accurate methods to assess and discriminate grape and wine aromas outside the laboratory. Therefore they used an electronic nose to analyse the 'aroma' of grapes. The researchers used an e-nose to classify commercially-produced wine grapes according to their geographical origins or ripening stage.
Developing an objective measure of the properties of grapes and wine will allow winemakers to use more precise methods to grow grapes with desirable qualities.
Developing an objective measure of the properties of grapes and wine will allow winemakers to use more precise methods to grow grapes with desirable qualities. For example, an electronic nose could allow winemakers to test hundreds of grape samples in a few hours and plan their farming techniques accordingly.
This approach is also a step towards allowing winemakers to estimate the properties of the finished wine based on measurements of the grape juice. This has traditionally been difficult, as many of the flavour and aroma qualities that affect the quality of the finished wine are locked up in a non-volatile form in the grape.
Predicting the quality and other properties of wine-grape juice would allow growers to tailor their crops to wine styles that are in demand.
Who was involved
The research was lead by Dr Ciaran Forde, Dr Paul Boss, Dr Brian Loveys and Dr Rob Bramley of the Food Futures Flagship and included scientists from:
- CSIRO Food & Nutritional Sciences
- CSIRO Plant Industry
- CSIRO Ecosystem Sciences
- CSIRO Mathematical and Information Sciences.
Find out more about our work in Cracking the code for wine flavour.