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FERMENTATION


To convert the sugars in the wort into alcohol, a fermentation progress is necessary and therefore yeast must be added. As yeast can’t stand hot temperatures, the wort is cooled down to about 20°C before it is married with the yeast in one of our 9 fermentation tanks (or wash backs), each of which store 15,000 litres. After yeast is added to start the fermentation process, the solution, now called wash, is left in the wash back for around 48 hours. During this time the yeast spits glucose molecules in the wash, with each glucose molecule producing two ethanol molecules (which is the alcohol we need), two carbon dioxide molecules and heat. We can experience this reaction using three senses. The alcohol can be smelled. The carbon dioxide itself cannot be seen, but the reaction it causes can - the bubbles in the mash and foam produced. And then there is the resulting heat that can be felt by putting a hand on the washback. As the lauter tun produces wort every 6 hours or so, 9 tanks are required so that fermentation in the 1st tank is ready by the time the 9th is filled. During fermentation, the yeast creates a lot of CO2 and excess heat. If wash backs are placed in a cold environment the fermentation process is slower and the whiskey is said to taste better. So, all our wash backs have cooling jackets which are computer controlled to keep the liquid at a constant temperature. We also have a system to collect the CO2 to stop it building up in the distillery, plus an automated anti-foam system to monitor and manage any excess foam production. After fermentation the wash will end up with an alcohol concentration of about 6 to 10 percent. This is adequate for a nice beer, but not enough for a whiskey, so it’s time for the next step, distillation.


 
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