UNDERSTANDING YEAST

Yeast helps bread to rise and gives it flavor and smell. Two types of yeast are used in baking:

• A wild pre-ferment or sourdough starter: This is yeast made of microorganisms that grow naturally when a mass of flour, water, and salt is left for several days. Flour and water are occasionally added to feed the yeast.

• Pressed yeast or baker's yeast: This is industrially cultivated Saccharomyces cerevisae yeast, pressed into a mass in which the number of microorganisms present is much higher than in sourdough starter.

Pressed yeast allows for a quicker fermentation process, but results in bread with less flavor. In order to facilitate mechanization and substitute changes that occur in dough during a slower fermentation, baker's yeast also has industrially synthesized supplements and additives.