Yeast Preparation

Yeast usually require preparation. The form of yeast typically used in winery production comes in a dried state, sold in vacuum packed containers, and must be hydrated and acclimatized to the juice that it will inoculate. To do so, one must mix the yeast into warm water then slowly add a portion of the juice it will inoculate into the yeast medium. First, the winemaker must measure the volume of juice being fermented. The corresponding amount of yeast is then weighed out for preparation. The standard recommended rate of addition for yeast to juice is 200 mg of yeast per liter of juice. An amount of water weighing 10 times the weight of the yeast is then prepared. The water’s temperature should ideally be 40°C (104°F). If the water is too cold, the yeast will not properly dissolve and hydrate, if it’s too hot, it will kill the yeast. The dried yeast is mixed into the warm water until dissolved, then allowed to stand for 20 minutes. After that time, a portion of juice equal to half the yeast slurry volume is added to the yeast preparation. This will provide it with sugar and begin to move the temperature of the yeast preparation towards that of the juice it will inoculate. Let the yeast rest another 20 minutes after each juice addition. Continue to add juice that the yeast will inoculate in the half volume fashion until the yeast preparation is within 5°F to 10°F of the temperature of the juice. The yeast is ready for inoculation once the temperature range has been reached.