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1. 1. Yeast

   • Temperature
     • 1. 34°F (1°C) – inactive, storage temperature
       • 2. 60° to 70°F (15° to 20°C) – slow action
         • 3. 70° to 90°F (20° to 32°C) – best growth; proofing temperature for bread doughs
           • 4. Above 100°F (38°C) – reactions slow
             • 5. 140°F (60°C) – yeast is killed
   • Forms of yeast
     • 1. Fresh yeast (compressed yeast) - moist and perishable and preferred by professional bakers.
       • 2. Active dry yeast - must be rehydrated in 4 times its weight of warm water- about 110°F(43°C)- before use.
         • 3. Instant dry yeast - does not have to be dissolved in water before use.
   • Meaning
     • - By fermentation process
       • - Acts on carbohydrates and change into carbon dioxide gas and alcohol.
         • - The alcohol evaporated completely during and immediately after baking.

2. 2. Chemical Leaveners

   • i. Baking soda – is the chemical sodium bicarbonate. If moisture and acid present, soda release carbon dioxide gas which leavens the product. Acids that react with soda include honey, molasses, buttermilk, fruits, cocoa and chocolate.
   • ii. Baking powder – is the mixture of baking soda plus an acid to react with it and more versatile because do not depend on acid ingredients.
     • Single-acting baking powder - require only moisture to be able to release gas. Can be used only if the product is to be baked immediately after mixing.
     • Double-acting baking powder- require heat for complete reaction. Can stand for some time before being baked.
   • iii. Baking ammonia – Is the chemical ammonium carbonate. Need heat and moisture for it to work. Can be used only in small products, like cookies that can allowed the ammonia gas to be completely driven off.

3. 3. Air – incorporate into 2 method. Air is expand during baking and leavens the product.

   • i. Creaming – process of beating fat and sugar together. An important technique in cake and cookies making. Also, some pound cakes and cookies are leavened by this method.
   • ii. Foaming – process of beating eggs, with or without sugar. This technique are used to leaven sponge cake, while angel food cakes, meringue and souffles are leavened with egg white foams.

4. 4. Steam - puff pastry, cream puffs, popovers and pie crust use steam as their major or only leavening agent.