Wine profiling with GC/MS
The world wine industry is currently going through a very innovative phase at virtually all stages, from the grape to the consumer, using different fermentation techniques, different yeast strains, ageing, and wood treatment, amongst others. There are also options regarding final treatments prior to bottling, filtration package closure, storage in cellar, transport and storage at point of sale. All impact on the flavour and quality of the wine, and Gas Chromatography Mass Spectrometry (GC/MS) is being increasingly used to profile products.
We frequently help our clients in the wine industry to identify why a problem has arisen, such as a taint, a flavour or aroma defect, a sediment or haze or simply capping of aroma or flavour. Sensory assessments are a valuable tool, but we are frequently involved in disputes between companies, and sensory analysis may have restricted use in these situations. Answering questions such as who is responsible for an issue and identifying whether the problem lies with the producer, transporter/ shipper or importer requires state–of–the–art science.
GC/MS is a powerful technique which separates and identifies key components within the wine down to nanogram per litre levels. Both aroma and flavour compounds are separated and identified. Then, by overlaying chromatographic profiles, changes within a wine can be monitored. There is also the option of a second mass spectrometer, which splits the individual molecules in order to achieve even greater sensitivity and specificity. We also use the very latest technique, time of flight (ToF/GC/MS), which enables us to detect and identify unknown or unexpected compounds within wine without the need to know in advance what we are looking for.
As an example, some pleasant primary aroma compounds can be shown to increase; others, possibly unpleasant, increase while some compounds denature and others may appear. Utilising the overlaying technique by graphical representation, differences can relatively easily be visually demonstrated.
Examples: variety, vintage, heat damage
- In a Sauvignon Blanc blended with a cheaper variety, one batch was much less aromatic and shown to have less Sauvignon Blanc in the blend.
- An imported wine was tasted on receipt and found to taste tired/old. GC/MS profiles were compared (buying sample verses imported stock) and different compounds, which were markers of heat damage, were detected in the suspect stock. This highlights how important it is to store wines correctly and care should be taken when exporting. Excessive heat can dramatically reduce wine quality and shelf life.
- A major branded variety was compared against its competitors in order to try and identify points of difference. Variables were minimised by using freshly bottled wines from the same vintage at the same time point. Differences were noted.
The potential of profiling wines using GC/MS is significant and used correctly it should be a considerable asset to the developing UK industry.