1. LEAVENING AGENTS

2. DEFINED Aerates mixture  increases volume and lightens it Leavening action may be produced by physical, chemical, or biological means Common leavening agents: air, steam, carbon dioxide

3. AIR Introduced by sifting dry ingredients, creaming and mixing batters, and incorporating beaten egg whites All flour mixtures depend on air, but it is not sufficient Creaming fat and sugar for aeration traps carbon dioxide from chemical leavening Kneading incorporates air in yeast breads – carbon dioxide expands air cells Air importat for fine, even grain of baked products

4. STEAM Used because volume of water increases more than 1600 times as it vaporizes and expands Steam alone not sufficient-combine with air or carbon dioxide Recipes are liquid batter (popovers)-volume of flour=volume of liquid Must use high temperatures so boiling point reached quickly

5. CARBON DIOXIDE Generated by chemical leaveners or produced from sugar by yeast Time of release important: some during mixing so fine bubbles will be dispersed Fine dispersion=fine crumb and thin cell walls Emulsions maintain gas emulsion in batter Major portion of carbon dioxide released in oven before crumb is set

6. BAKING SODA Sodium bicarbonate heated  sodium carbonate (washing soda), water, carbon dioxide 2NaHCO 3  Na 2 CO 3 + H 2 0 + CO 2 Reaction is slow Produces alkaline salt (disagreeable flavor)

7. ALKALINE SALT In excess  alkalinity changes flavonoid pigments in flour to yellow color Increases browning by Maillard reaction Product slightly yellow with brown spots If sodium combines with fatty acid  bitter soapy taste

8. BAKING SODA + ACID Avoid problems Produces neutral salt residue + carbonic acid NaHCO 3 + Hx  NaX + H 2 CO 3 Carbonic acid readily  H 2 O + CO 2 Carbonic acid unstable

9. COMMON ACIDS Lactic acid in sour milk, buttermilk, yogurt Aconitic acid in molasses and brown sugar Gluconic acid in honey Malic acid in apples and pears Tartaric acid in grapes Succininc, citrus and benzoic acids in fruits and vegetables Acetic acid in vinegar Usually: buttermilk, lemon juice, vinegar, molasses

10. PROPORTIONS 1 C Milk – replace 1 T with vinegar or lemon juice = sour milk 1 C Milk – add 1 ¾ tsp cream of tartar Baking soda – ½ tsp neutralizes 1 cup fully soured milk ½ tsp baking soda needs 1 ¼ tsp cream of tartar for complete reaction Reaction takes place ONLY in water

11. BAKING POWDER Mixture of baking soda + acids or acid salts separated by inert filler Federal Standards – must yield >12% carbon dioxide Inert filler = buffer, standardizes strength of powder Acids and baking soda must ionize

12. IDEAL BAKING POWDER Releases some carbon dioxide at room temperature Releases most in earlier part of baking No aftertaste

13. SUBSTITUTE ½ teaspoon baking soda equivalent to 2 teaspoons baking powder

14. CLASSIFICATION OF BAKING POWDERS

15. ACID CONTENT Tartrate powder Phosphate powder Combination powder – sodium aluminum sulfate and monocalcium phosphate

16. REACTIONS Single acting – fast, produces CO 2 as soon as moistened, acid soluble in cold water Double acting – slow, reacts twice: once when moistened and then when heated Contains two acids: SAPP – Phosphate powder reacts to moisture; sodium aluminum powder (SAS) reacts to heat

17. BIOLOGICAL LEAVENING

18. YEAST Needs food, warmth, moisture Fermentation – enzymes (zymase) convert sugars to alcohol and carbon dioxide Carbon dioxide retained in gluten structure Alcohol evaporates CANNOT use lactose for fermentation

19. BACTERIA Need controlled conditions: temperature, moisture Grow and act on sugar  CO 2 and hydrogen Occur naturally in cornmeal  create a sponge to leaven salt-rising bread Sourdough bread