Raising-Agents

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Exam code:8585

Cooking with raising agents

The role of a raising agent is to cause a mixture to rise; this is achieved as follows:
1. bubbles of gas are introduced into a mixture
2. heating causes the gas to expand and the mixture rises
3. the resulting air pockets within the cooked mixture produce a light, airy texture

Examples include:
- chemical raising agents
- mechanical raising agents
- steam
- biological raising agents

Chemical raising agents react to produce the gas carbon dioxide; it is this gas that causes the mixture to rise
Chemical raising agents include:
- bicarbonate of soda
  - Bicarbonate of soda releases carbon dioxide when it is heated in the presence of liquid and an acid
  - It has a soapy flavour due to its alkaline nature, so tends to be used on its own only in strongly flavoured items, e.g.
    - soda bread
    - gingerbread
    - fruit cake
- baking powder
  - Baking powder contains bicarbonate of soda and cream of tartar; the acidic cream of tartar neutralises the alkaline baking soda, removing the soapy flavour
  - It can be added as an ingredient to baking mixtures, and is also present within self-raising flour

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Mechanical raising agents work to trap air within a mixture; this air then expands during cooking and causes the mixture to rise
Methods of trapping air within a mixture using mechanical methods include:

Method	Description	Example
Whisking	A whisk is used at high speed to trap air within a mixture	Egg whites, cream
Beating	A mechanical mixer, wooden spoon or fork is used to mix ingredients together quickly	Pancake batter
Folding	A spoon is used to move the mixture over repeatedly	Stirring flour into a cake mixture
Folding	Dough is folded back on itself multiple times	Puff pastry
Sieving	A sieve is used to add flour or icing sugar to a mixture; this breaks up the particles and traps air in between	Adding flour to a cake mixture
Creaming	Fat and sugar are beat together, trapping air within an aerated mixture	Cake mixture
Rubbing in	Fat and flour are rubbed together; this process traps air between the flour particles	E.g. scones, biscuits, pastry

When food is cooked, heat causes water within it to boil and turn into steam
In foods with a high water content the rising steam can cause the mixture to puff up, e.g.
- yorkshire pudding batter
- choux pastry dough

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Yeast is a living organism, so is referred to as a biological raising agent
Yeast functions as a raising agent as follows:
1. yeast is added to the dough and the dough is left in a warm place for a period of time known as proving
2. during proving the yeast begins to respire using sugar in the mixture as its fuel; this produces carbon dioxide gas as a waste product
  - Once the yeast cells run out of oxygen they start to produce alcohol as an additional waste product; this anaerobic process is known as fermentation
3. the carbon dioxide gas causes the dough to rise
4. heat during baking causes the gas to expand further and increases the rise
  - Baking kills the yeast and also causes any alcohol that may have been produced during proving to evaporate
For a biological raising agent to function effectively the following are required:
- the dough must contain liquid so that a gluten network can form
- the environment must be warm enough for the yeast cells to respire at a high enough rate, e.g. 25-29 °C
- sugar must be present in the dough to provide fuel for the yeast
Examples of foods that are produced using biological raising agents include:
- bread
- doughnuts
- croissants

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