Wednesday, 17th June was a very exciting day at Rathfinny Estate as we bottled roughly 5,600 bottles of our first sparkling wine! We’re not bottling one million bottles a year yet, but that will come faster than we think.
The base wine already had about 11% v/v alcohol, and we added sugar for the second fermentation, which will increase alcohol by 1,5% v/v. A critical factor for this bottling was the preparation of a good yeast culture.
The first fermentation is relatively easy for yeasts because the environment is particularly favourable; there is plenty of sugar, no alcohol yet, and low levels of SO2 in the must. One can rehydrate dry yeasts and add them directly to the must, and it should ferment nicely.
For the second fermentation, however, the environment is notably difficult for yeasts: There are higher levels of SO2 and a high alcohol concentration. Alcohol is toxic to yeasts! If you tried to add the yeasts directly to that wine, well, they would die very fast and the wine would not re-ferment. Instead, one needs to slowly adapt the yeasts to this harsh environment by progressively adding some of the base wine into the culture. That way, yeasts have time to multiply and get used to the change of environment.
Temperature is another critical point: while yeasts need to be rehydrated at 30 to 35 Celsius, they inoculate a wine at 13 Celsius (cellar temperature). Yeasts would thrive in a 20 to 25 Celsius environment and 13 Celsius is a low temperature for them. The temperature of the culture needs to be dropped down gradually as well. Usually after about a week, the culture is healthy, with a good amount of viable yeasts ready to be added to the base wine just minutes before bottling.
It will now take a few weeks for the second fermentation to come to an end, and the wine will officially be sparkling! Ageing approximately three years on the lees (after the yeasts have nothing to consume and die in the bottle) will work “magic”, adding subtle flavours and complexity to the wine. So the keyword for now is: Patience!
A happy owner…