4 Chapter 4-Types of leavening gases

You remember from our previous chapter that there are three categories of leavening:

1. Physical
2. Biological
3. Chemical

From these three types of leavening, three gasses are produced to create the volume and puff needed in baked goods.

Physical Leavening produces:

• Air–
  • Air is created during the mixing of your product.  Air pockets are formed during the creaming of solid fat and sugar.  Air pockets are also created during the whipping of egg whites or heavy cream.  In smaller amounts, air is even trapped during the sifting of dry ingredients.
• Steam–
  • Steam is created when a liquid evaporates with the heat of the oven.  For example, when pate a choux batter is baked, the liquid from the eggs evaporates causing the choux paste to puff into a ball.  Meanwhile, the oven’s heat is drying out the shell of the choux, creating structure.  At the end of the baking process, the choux pastry is crispy on the outside and hollow in the middle due to the evaporation of liquid.
  • Similarly, in pie crust, the butter pieces melt in the oven and the liquid in the butter (remember that butter is about 80% fat and 20% liquid) evaporates creating the traditional flaky pie crust texture.

All baked goods rely on physical leavening to some extent since all baked goods contain some amount of water (which turns to steam) and have some air incorporation (from mixing).  The air created during mixing AND steam from evaporating liquid expands with the oven’s heat, creating volume.

Biological and Chemical Leavening produce:

• Carbon Dioxide
  • Carbon Dioxide is the only one of the three main leavening gases not present in all baked goods.
  • It is formed through yeast fermentation or through the addition of a chemical leavening agent.  
    • As noted previously, we will focus on chemical leavening in this module, biological leavening will be reinforced at a different time.