Tasting grapes - a remarkable aftertaste
Time for some wine science. There was an interesting aside in Denis Dubourdieu's paper at the recent Austria conference. Denis is the man responsible for identifying a group of sulfur-containing compounds called thiols as being important in the aroma of Sauvignon Blanc.
Now thiols are made by yeasts from precursors present in the grapes. In the must, these precursors are odourless. The late Emile Peynaud, another famous wine scientist, remarked that 'it is winemaking that reveals the aroma hidden in the fruit'. Denis recalled how Peynaud talked about the aftertaste of Sauvignon grapes: 30 seconds after swallowing, you suddenly get all these lovely aromatics which weren't there earlier.
This reflects the transformation of precursors to aromas by the enzymes in the mouth. I was reminded of this comment when I tasted some almost ripe Phoenix grapes in my back garden today. They didn't taste of all that much, but after a minute or so I was getting these remarkable passion fruit/gooseberry aromas in the back of my nose.