Well we started to harvest this year. The first grapes to be picked is some Sauvignon Blanc. This is very early (it is not yet February), but it is not a sign of global warming. In fact the harvest seems to be slightly later than normal.
The reason for the early harvest is that we are chasing that elusive compound that Sauvignon Blanc contains called methoxy pyrazine, or just called pyrazines in the industry. Pyrazines are the chemicals that give Sauvignon Banc that herbaceous, grassy flavour. Other descriptors include green pepper, asparagus, and green fig. Cabernet Sauvignon also contains this chemical, although it is generally undesirable, as it gives a green dusty flavour.
The problem with pyrazines is that they are sensitive to heat, and decrease with ripeness. That is why we harvest some of the Sauvignon Blanc early. The grapes have not been exposed to many hot days, so still contain high levels of the chemical. The grapes have a very low sugar (so low alcohol), and a very high acidity. The resulting wine will not be very pleasant, as it will taste thin, and hard from all the acid. But this is what we call building block.
We will use this wine at a rate of about 30% in the larger blend. The remaining wine will be more tropical flavoured, and taste fuller due to the higher alcohol. The early picked Sauvignon will just add that typically grassy character of the Sauvignon Blanc. Think of it as salt in your food. Salt on its own is inedible, but a little bit in your food makes a huge difference.