Raising Agents. Flashcards
What is a raising agent?
A raising agent is a substance that is added to flour mixtures which can be chemical, physical or biological which will produce carbon dioxide and cause the mixture to rise and have a light, pleasant texture.
What are raising agents used for?
Raising agent are used to introduce a gas into the mixture.
What do gases do when heated?
Gases expand when heated, and can raise a mixture in the process.
What are the 3 gases used as raising agents?
- Carbon dioxide.
- Air (a mixture of gases).
- Steam (water in a gaseous state).
What are three categories raising agents fall into?
- Mechanical raising agent (physically incorporated).
- Chemical raising agent (commercially made).
- Biological (living organism e.g. yeast).
What are the 5 methods of mechanical raising agent?
- Sieving.
- Creaming.
- Whisking.
- Folding and rolling.
- Rubbing in.
How is sieving a form of incorporating air and give an example?
Air becomes trapped between its many fine particles e.g. flour for chocolate biscuits.
How is creaming a form of incorporating air?
Air becomes trapped in the form of tiny bubbles e.g. fat and sugar (Victoria sponge).
How is whisking a form of incorporating air and give an example?
Eggs and sugar trap large volumes of air e.g. eggs (swiss roll).
How is folding and rolling a form of incorporating air and give an example?
Air is trapped between layer, and sealed in e.g. rough puff pastry.
How is rubbing in a form of incorporating air and give an example?
Air is trapped as the fat is rubbed into the flour e.g. scones.
How is carbon dioxide incorporated into mixtures using chemical raising agent (3 ways)?
Bicarbonate of soda - alone.
Bicarbonate of soda plus an acid.
Baking powder (contains bicarbonate of soda and acid).
What are the 3 objectives of using bicarbonate of soda (an alkali)?
Has an unpleasant taste.
Has a yellow discoloration.
Usually used for strong-flavored mixtures such as gingerbread.
What does the acid in the bicarbonate of soda plus an acid do?
The acid helps prevent the unpleasant washing soda taste and color.
What are the four acids you can use with bicarbonate of soda?
- Cream of tartar.
- Tartaric acid.
- Lactic acid (in sour milk).
- Citric acid (lemon juice).
What are 2 benefits and disadvantages of using cream of tartar with bicarbonate of soda?
- Often used.
- Produces a colorless residue and is almost tasteless.
What are 3 benefits and disadvantages of using tartaric acid with bicarbonate of soda?
- Not used often.
- Very effective.
- Resulting residue is slightly bitter.
What are 3 benefits and disadvantages of using lactic acid (in sour milk) with bicarbonate of soda?
- Produced by lactic acid bacteria.
- Not very accurate.
- Often used in scone making.
What is benefit and disadvantage of using citric acid (lemon juice) with bicarbonate of soda?
- Not very accurate - hard to gauge strength of the acid.
What 3 things does baking powder consist of?
- Bicarbonate of soda.
- Acids.
- Starch.
What would happen to bicarbonate of soda and acid if any moisture was absorbed from the atmosphere from the starch in it?
This would cause a reaction between the bicarbonate of soda and acid releasing carbon dioxide, making the baking powder ineffective.
How is self-raising flour prepared?
Self-raising flour is prepared from soft cake flour and a standard strength raising agent.
What is self-raising flour useful for?
It is useful for plain cake mixtures (fruit cake and rock cakes).
What 5 things are self-raising flour not suitable for and why?
- Scones - too weak on its own.
- Rich cakes - too much raising agent.
- Bread, pastries, biscuits - chemical raising agent not required.
