Natural flavours of wine: correlation between instrumental analysis and sensory perception

Summary

The aroma of wine consists of 600 to 800 aroma compounds from which especially those, typical for the variety, are already present in the grapes. The aroma extracts — received by extraction with trichlorofluoromethane — are separated by gas chromatography. There are significant varietal differences between the aromagrams (“fingerprint pattern”). Thus the amount of some flavour compounds (“key substances”) shows typical dependence on the variety. Especially monoterpene compounds play an important role in the differentiation of wine varieties.

The German white wines can be differentiated into three groups only by quantitative determination of 12 monoterpenes (“terpene profile”). These groups are: “Riesling type”, “Muscat type” and “Silvaner-Weißburgunder type”. Such “terpene profiles” are also useful for the separation of real Riesling wines from others called Riesling (e.g. Welschriesling, Kap Riesling, Emerald Riesling) but not produced from grapes of the variety Riesling. Including further components and by means of statistical methods as for example linear discriminant analysis even the different varieties within the mentioned groups (for instance the “Riesling”-group: Riesling, Kerner, Ehrenfelser, Bacchus, Müller-Thurgau) can be separated from each other.

To identify compounds causing “off-flavours” the sniffing technique is the method of choice. The off-flavour is pinpointed during gas chromatography separation of the complex aroma mixture by effluent sniffing. Once allocated, the chemical nature of the off-flavours is elucidated by spectroscopic methods. Substances contributing to the green pepper taint, the strawberry note, mousiness, corkiness etc. in wine could be found in this way.