1. Leavening Agents
Gases expand greatly when they are heated, unlike gases and liquids. There are many different types of leavening agents.

2. Leavening is the production or incorporation of gases in a baked product to increase volume and to produce shape, and texture.
The three main gases that leaven baked goods. Two of these gases, steam and air, are present in all baked goods.
Air
Carbon Dioxide
Steam
Formation of air cells is important during mixing.
Leavening gases are trapped in these air cells.
Walls are formed of gluten proteins and egg proteins, holding gases in and forming structure.
Exact measurement of leavening agents are important because small changes can produce major defects in a baked product.

3. Yeast Yeast Fermentation:
It is the process by which yeast acts on sugars and changes them into carbon dioxide gas and alcohol. The release of this gas produces the leavening action in yeast products. The alcohol evaporates completely during and immediately after baking. Yeast is a microscopic plant that accomplishes this fermentation process by producing enzymes.
Yeast
Yeast is the leavening agent in breads, dinner rolls, Danish pastries and similar products.

4. Because Yeast is alive, it is Sensitive to Temperatures!!!!!!!
34*F Inactive (storage temp.)
60-70*F Slow Action
70-90*F Best Growth (fermentation & Proofing for bread dough)
Above 100*F Reaction Slows
140*F Yeast is Killed
Yeast also contributes to flavor. The longer the fermentation, the stronger the flavor.

5. Types of Yeast Fresh Yeast Active Dried Yeast
Moist and perishable
Preferred by professional bakers
Purchased in 1# cakes lasting 2 weeks
Can be frozen 4 months
Avoid using if discolored or moldy
Dry, Granular Form of Yeast
Must be rehydrated 4 times its weight in warm water before use
25% of yeast cells are dead due to harsh drying process
Presence of the dead cells can have a negative effect on dough quality
Not popular with baking professionals

6. Another Type of Yeast…Instant Dry Yeast!!!
New product invented in 1970”s
A dry, granular form of yeast, but does not have to be dissolved in water before use.
It contains very little dead yeast, so less is needed.
The preferred method of use is mixing it into the flour.
It produces more gas and quickly.
Sometimes called rapid rise or quick rise yeast.

7. Chemical Leaveners Baking Soda Baking Powder Baking Ammonia
If moisture and an acid are present, soda releases carbon dioxide gas, which leavens product.
Heat is not necessary for this reaction. Product must be baked at once.
Baking Powder
Are mixtures of baking soda plus one or more acids to react with it.
They also contain starch to prevent lumping.
Do not use more than needed because undesirable flavors may be created.
Baking Ammonia
Only heat and moisture are necessary for it to work.
No acids are needed and no residue can affect flavor.

8. Other Leaveners….. Air Steam Creaming Foaming
Beating of fat & sugar to incorporate air.
Some pound cakes and cookies are leavened entirely by this process.
Foaming
Process of beating eggs, with or w/o sugar, to incorporate air.
Foams made with eggs are used to leaven sponge cakes, angel food cakes and meringues.
When water turns to steam, it expands 1100 times its original volume.
Because all baked products contain some moisture, steam is an important leavening agent.
Examples: Cream puffs, popovers, pie crusts.
If the starting temperature is high, leavening is at its greatest.