Yeast and Other Leaveners

Leavening, the main function of yeast, occurs when yeast produces carbon dioxide (CO₂). Alcohol, acids, and energy (heat), the other by-products of yeast fermentation, biochemically condition the flour by mellowing and softening the protein and contribute to the flavor of the finished product. The average (fresh) yeast content of most bread doughs is 2 to 5 percent based on flour weight. In the bakery, yeast is principally controlled through the regulation of times and temperatures, but food supply, water, and the pH of the dough will also affect the rate of yeast activity. Understanding what influences yeast activity gives the baker added control over the fermentation process.