Use this ratio – 2 to 4 grams of dried yeast for every gallon of mash. The foamy, rocky head of yeast called kraeusen, should form during the first four hours of fermentation. It could lag up to 24 hours which should be fine. You have to pitch in some more yeast if it takes longer than a day to form.
The “100 grams of dry yeast per 5 gallons” rule only applies to a pure sugar mash where you aim to turn it into vodka or as a base spirit for liquors. Fermenting a wort with more than 4 grams of yeast per gallon will effect undesirable sulfur flavors that can be difficult to get rid of.
However, take note that over pitching would be preferable than under pitching yeast. Over pitching can get you some off flavors but they can be eliminated with a lot of copper exposure and secondary ferment. While, under pitching results to a long lag time that makes the mash at risk of contamination.
During the fermentation, we want to keep the yeast happy so it can make the most out of our sugar. So we keep them fed and provided with proper nutrition. By saying that, nitrogen must be present! DAP (Diammonium phosphate) is usually used as yeast nutrient. Ammonium salts or ammonia are also great sources of nitrogen. A sugar wash typically needs 2 ml. of ammonia per liter of mash.
Also, do not supply the yeast with excessive nutrients, it won’t push them to work faster anyway. It might even kill them.
Your yeast requires a slightly acidic environment to survive and multiply, which also helps restrain bacterial contaminants. It is advisable to maintain the mash a pH of about 4.0-4.5 before fermentation. Citric or lactic acids will help you do that. Lemon juice can be a great and cheap alternative! You can always double-check the pH using pH papers.
Temperature is another key to successful alcohol yield. At some point, the temperature the yeast is submitted can degrade the flavor of the final distillate. When using ale yeast to make whiskey, the temperature should be between 60 to 70 F. Lower than this range will hold back the yeast from converting sugar which makes the mash at risk of infection. Higher temperature will effect stress reactions on the yeast that causes higher alcohol formation and ester. The result is an undesirable solvent-like flavor that can sting the taste of the final alcohol.
Regulating the temperature in cooler environments can be quite difficult to do. A few tricks you can do:
- Using a water bed heating pad, wrap the fermenter around and attach the thermostat to the side of it. Wrap them all up with a blanket.
- Keep the mash vessel inside a hot water cupboard.
Submerged the fermenter in a drum filled with warm water and then secure an immersion heater to keep the water warm.
Posted by Jason Stone on