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LEAVENING AGENTS

LEAVENING AGENTS. 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. AIR.

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LEAVENING AGENTS

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  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 • 2NaHCO3Na2CO3 + H20 + CO2 • 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 • NaHCO3 + Hx  NaX + H2CO3 • Carbonic acid readily  H2O + CO2 • 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 CO2 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  CO2 and hydrogen • Occur naturally in cornmeal  create a sponge to leaven salt-rising bread • Sourdough bread

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