1. Dough and batter ingredients: Yeasts and chemical leavenings

2. Leavenings
Leavenings are the ingredients that fill doughs and batters with bubbles of gas
This makes the amount of solid material in a given volume less, making the product less dense

3. Yeasts
Louis Pasteur, 150 years ago, studied a particular class of fungus called yeast
Yeasts undergo fermentation – a gas producing process

4. The Fungi
Yeasts are a group of microscopic, single celled fungi, relatives to the mushroom
Some cause infection, some cause food spoilage, and some are used in brewing and baking

5. Where did they come from?
Yeasts were fist obtained from grain surface, supplied by an earlier piece of dough, or from the surface of beer brewing vats

6. Where are we now?
Strains of yeast specifically for bread making are grown on molasses in industrial fermentation tanks

7. Yeast metabolism
Yeasts metabolize sugars for energy and produce carbon dioxide and alcohol
C6H12O C2H5OH + 2CO2

8. Fermentation
In making beer and wine, the carbon dioxide escapes leaving the alcohol behind
With bread, the carbon dioxide and alcohol get trapped, then are expelled from the dough during baking

9. Using sugars in dough
Yeasts grown on glucose, fructose, and maltose which enzymes in the flour produce from broken starch granules
A small amount of sugar added will increase yeast activity, while a large amount will decrease it as does table salt

10. The importance of temperature
Cells grow and produce gas most rapidly at around 94 degrees Fahrenheit
Our challenge will be the cold temperatures in the kitchen