Yeast from most producers is used interchangeably by bakers, but there are differences among yeast plants, suppliers, and over time. Some of the variations are the result of adjustments that yeast producers and bakers have to make to use a single type of yeast for several different applications. Bakers can take advantage of the variations and tradeoffs to expand their own quality and reliability and reduce costs.
The potential characteristics of a particular baker’s yeast are determined by its strain. Large number of Saccharomyces cerevisiae strains has already been selected for baking. All Saccharomyces cerevisiae yeasts have certain similarities, including the substances they use for growth, how they reproduce, and their appearance under the microscope. But individual strains also have important differences, like how much sugar they will tolerate, how quickly they grow, and how sensitive they are to calcium propionate. The actual characteristics of baker’s yeast from a particular strain are determined by its composition. Baker’s yeast is grown on molasses by starting with a small culture of the desired strain and controlling the temperature, nutrients, and aeration so that it multiplies. The growth conditions affect how fast the yeast multiplies and how much protein and carbohydrate it accumulates. Rapid growth usually means more protein, more enzymes, and more initial activity. Slow growth usually means more carbohydrate, lower initial activity, and better stability. Baking recipes and ingredients affect yeast performance. Lean dough’s require yeasts with high maltase enzyme activity because maltose sugar from flour is the primary energy source.
Sweet, salty, and low absorption dough’s require yeasts with good osmotic tolerance because the amount of available water is limited. Recipes with sours, fruit, calcium propionate, and natural mold inhibitors also inhibit different yeasts to different degrees.
Baking processes also affect yeast performance. Straight and no-time dough’s work best with fast yeasts that adapt quickly to give good oven spring. Sponge and dough systems work best with slower yeasts to retain sufficient activity for the final proof. Frozen dough systems work best with slow yeasts that retain their activity well. Yeast producers make tradeoffs that affect performance in different applications. The strain choice determines sweet versus lean dough performance and influences suitability for different baking processes. The yeast composition optimizes for either activity or stability, and also influences suitability for different baking processes.