EXAM 3: Leavening Agents Flashcards
What are the three major leavening agents
Physical: yeast breads and quick breads
Biological: yeast breads
Chemical: quick breads
What are the two types of biological agents
Bacteria: basis of the “starter” culture
Yeast
How is bacteria used as a leavening agent
It is the basis of the “starter” culture
-starter: culture of microorganisms, usually bacteria and/or yeasts used in the production of certain foods such as sourdough bread, cheese, and alcoholic beverages
- lactobacillus sanfrancisco is one classic variety
- use maltose to produce lactic acid and acetic acid
- low pH produces sour dough and favors other specific yeasts
How is yeast used as a leavening agent
Yeast: saccharomyces cerevisiae
Requires sugar for fermentations
- sugars found in flour (maltose>glucose - formed from addition of enzymes activated during milling)
- added simple sugars (sucrose or honey)
Sugars fermented into CO2 and ethanol
Yeast (without oxygen) + C6H12O6 -> 2C2H5OH + 2 CO2 (gas)
Yeast + glucose -> ethanol + carbon dioxide
What are the two forms of yeast
Active and Inactive
What is active yeast
Bakers yeast
Brewers yeast
- yeast for alcoholic bevs
What is inactive yeast
Dried brewers yeast and primary-grown yeast
Used for nutritional value and flavor
What are the types of active yeasts
Dry yeast and instant yeast
What is dry yeast
Granular, low moisture
Long lie with refrigeration
Hydrate and activate by mixing in warm water (temps vary depending on the yeast type)
Dough requires 2 rising sessions
What is instant yeast
Added directly to the flour, then liquid is added to hydrate the yeast
No hydration before mixing
More active, more CO2
Shorter fermentation possible (i.e., bread machine)
One rising time, less flavor
What is the recommended temperature range of added liquid to rehydrate and activate active dry yeast dissolved in liquid
110-115 F
What is the recommended temperature range of added liquid to rehydrate and activate active dry yeast mixed with dry flour
120 to 130 F
What is the recommended temperature range of added liquid to rehydrate and activate quick rise (instant) yeast dissolved in liquid
110 to 115
What is the recommended temperature range of added liquid to rehydrate and activate quick rise (instant) yeast mixed with dry flour
120 to 130 F
What temperature kills yeast
Above 140 F
What temperature lowers yeast activity
Below 100 F
What are chemical leavening agents used for
Used to create rise in weak doughs and batters
Uses a reaction between alkaline and acidic compounds to create CO2
What are examples of chemical leavening agents
Baking soda and baking powder
What is baking soda and how does it work
Sodium bicarbonate
Reacts with an added acid and liquid in the batter to create CO2
What are examples of acid ingredients that react with baking soda
Buttermilk, yogurt, sour milk, honey, molasses, cocoa, fruit juice, cream of tartar
What happens if there is no acid present in a baked good with baking soda
Bitter, soapy flavor will result, product has a yellow color
What is the ratio of baking soda to flour
1/4 tsp baking soda per 1 cup flour
What is the reaction that occurs if there is no acid added to baking soda
What is the reaction that occurs with baking soda when there is an acid added to neutralize baking soda
What is baking powder
Baking soda plus an acid (acid in the form of solid crystals) and moisture absorbing agent
Residential formulation formulations are __________ _______ - contain two acids
What are the two acids
Double Acting
Acids:
Monocalcium phosphate (MCP)
Sodium aluminum sulfate (SAS)
Double acting baking powder has a 2-step release of CO2, what are the two steps
- When moistened at room temperature
- When heated in oven
- place the batter/soft dough in the oven as soon as it is in the baking pan
What are the affects of too much leavening agent
Product will fall, low volume
Coarse texture
Bitter taste (with sodium bicarbonate and SAS-phosphate powder)
Soapy flavor - poorly distributed baking soda
Cakes: cracked top
What are the affects of too little leavening agent
Compact, heavy product
What are examples of physical leavening agents
Air (gas bubbles) and steam
How does air (gas bubbles) work as a physical leavening agents
Gas bubbles are incorporated into almost all flour mixtures during mixing
- whipping eggs (creates foam)
- creaming fat/sugar
- sifting dry ingredients
Egg foams
- use egg protein for structure and air and steam to create the leavening
How does steam act as a leavening agent
Liquid ingredients in batter convert to steam, then dough expands
Ex: cream puffs, pastries
*most baked goods use air and steam as leavening agents
