Yeast dough leavening

Bakers Yeast Production. Bakers yeast is grown aerobicaHy in fed-batch fermentors under conditions of carbohydrate limitation. This maximizes the yield of yeast biomass and minimizes the production of ethanol. Yeasts grown under these conditions have exceUent dough leavening capabHity and perform much better in the bakery than yeast grown under anaerobic conditions. 

Hours contain very small amounts of sugars which are metabolizable by yeast (cf. Table 15.30). Addition of sucrose or starch s)frup at 1-2% to dough is advisable to maintain favorable growth of yeast and therefore to provide CO2 needed for dough leavening. Uniform leavening over an extended time improves the quality of many baked end-products the crumb structure acquires finer and more uniform porosity, while the crust has greater elasticity. 

Yeast (Saccharomyces cerevisae, Saccharomyces minor and others), which are mainly responsible for dough leavening, and a complex bacterial flora in which lactic acid-forming organisms dominate Lactobacillus plantarum, Lactobac, San Francisco and Lactobacillus brevis) are present in sour dough. 

Eggs. Eggs are not used much in breadmaking, except for specialty egg breads. Egg whites are occasionally used on the surface of hard roUs to impart a crispy cmst. Yeast-leavened sweet doughs or danish doughs often contain egg, up to 20%, based on flour, to achieve richness and to influence color and flavor. Some bakery foods, eg, sweet goods, croissants, and puff pastry, are often washed with egg wash (a mixture of egg and water or milk)... 

Presumably, at some point in history a batch of unleavened bread dough became contaminated with wild yeast and the first leavened bread was made. The only way in which such a system can be kept going is to keep back a portion of the old dough and add more flour and water to keep the fermentation going. In such a system various side-reactions occur and fatty acids start to be produced, hence the name. The acids give the dough some protection from contamination with undesirable moulds, which would be an advantage in a primitive society. 

There are various of these products made around the world. They are yeast leavened but based on a dough that is high in fat and sugar, possibly with egg added. 

No-time doughs - [BAKERY PROCESSES AND LEAVENING AGENTS - YEAST-RAISED PRODUCTS] (Vol 3)... 

---