Raising agents

Raising agents

1. WHAT IS A RAISING AGENT?

   • Air, carbon dioxide and steam
   • Chemical, biological and mechanical gas mixtures
   • Chemical - baking powder or baking soda to produce carbon dioxide gases
   • Mechanical - whisking, beating, sieving, etc, to trap air or add moisture
   • Biological - using yeast to produce carbon dioxide gases

2. HOW DO RAISING AGENTS WORK?

   • Moisture, heat or acidity (or all three) react with the raising agents to produce carbon dioxide gases.
     • As the mixture cooks, the gas bubbles make it rise by expanding and pushing it upwards
       • The gas bubbles then set in it and provides a sponge-like texture

3. AIR

   • Air is trapped in a variety of ways
     • Creaming
       • Fat and sugar are beaten together with a wooden spoon
         • Each bubble is surrounded by a thin layer of fat
           • The mixture changes colour during creaming as the trapped air creates a foam
             • Egg is added to the mixture to coagulate and form a wall around the bubbles, so that they can expand and raise the mixture
               • The mixture sets as the egg proteins coagulate

4. CARBON DIOXIDE

   • Produced by baking soda and yeast
   • Baking soda produces carbon dioxide gas when it is heated
   • If baking soda is used on its own, they would rise well, but the taste would be very unpleasant
     • To prevent this, baking soda is mixed with an acid called 'cream of tartar'
       • Mixing acids with alkalies will neutralise the taste, so that baking soda will not be produced

5. STEAM

   • Helps mixtures rise
   • When water is a liquid, the molecules join together with hydrogen bonds
     • When it is heated, the hydrogen bonds break and the molecules start to break free and go into the air as steam
   • Steam is only suitable for mixtures that contain a lot of water

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