Wine and beer makers have been using yeast, a single-celled fungal organism, to help make their alcoholic drinks for centuries. If sealed in a container into which no air can enter, yeast cells digest sugar and produce carbon dioxide gas and alcohol. This process is called fermentation. If you are dabbling with fermenting your own drinks, using the right amount of yeast in the fermentation process is critical. Knowing how much yeast to use involves one simple calculation.
Determine the volume of the container in which you will be fermenting your drink. Write the volume in liters. If you are using a container measured in gallons, you can convert it to liters using the following the formula:
N gallons x 3.785 = N liters
For example, if you are using a 5 gallon barrel:
5 gallons x 3.785 = 18.9 liters
Multiply the number of liters by 1.5, which is the recommended amount, in grams, of yeast necessary to ferment 1 liter of fluid (reference 1). An 18.9 liter barrel would therefore require:
18.9 x 1.5 = 28.4 grams of yeast
Ferment your measured amount of yeast in the liquid at a constant temperature. Tony Ackland of Home Distiller.org recommends fermenting your mash or wash at a constant temperature of 25 degrees C (45 degrees F).