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Year 10 - Raising Agents

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Alexandra Playford

on 3 July 2015

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Transcript of Year 10 - Raising Agents

Year 10 - Raising Agents
Lesson Objectives
Understand the different raising agents and how they are used in the production of food products.
Raising Agents
Consumers expect baked products such as bread and cakes to have a light and open texture. To create the desired texture and sufficient volume a raising agent is usually added.

The 3 most common raising agents are:

Air, Steam, Carbon Dioxide
How does a raising agent work?
The action of moisture or heat or acidity triggers a reaction with the raising agent to produce a gas.

Gas expands when heated.

The gas becomes trapped as it bubbles up through the mixture.

When heated the bubbles form a firm structure containing a network of tiny holes left by the expanded gases. This gives bread, cakes, scones a soft, sponge like texture.
Air
Air is a mixture of gases. Air is incorporated into mixtures using mechanical methods. Air can be added in different ways:

sieving flour - air is trapped between particles.

creaming together fat and sugar - air trapped in the mixture.

rubbing fat into flour - air is trapped as fat is rubbed into the flour

whisking and beating - egg white is capable of holding upto 7 tines its volume of air as the protein stretches eg meringue.

folding and rolling - air is trapped between layers
Steam
Water turns to steam when heated at 100 degrees. Steam can expand up to 1600 times its original volume. Steam only works as a raising agent in mixtures that have:

High amounts of liquid in the mixture i.e Yorkshire puddings.
High baking temperatures which allow the liquid to quickly reach boiling point.
Steam works during baking when:
The liquid reaches boiling point and steam is released.
Carbon Dioxide
Carbon Dioxide is incorporated into mixtures in two ways ie:

using chemical raising agents - such as bicarbonate of soda or baking powder.

Using biological raising agents - from the fermentation of yeast.

Carbon Dioxide gas is released into the dough and when heated teh gas expands the appearance of the product.
Chemical Raising Agents
These are powders that require liquid and heat to produce the carbon dioxide gas. They must be accurately measured and used in small quantities as they have strong characteristics that can affect the flavour, texture and appearance of a product.

Adding a chemical which causes a chemical reaction producing carbon dioxide. In an oven C02 gas expands and escapes from the mixture. Some of the gas escapes but some is trapped in the mixture as it cooks and sets.
Baking Powder
&
Bicarbonate of Soda
Baking powder is made from a combination of alkaline and acid substances that react when they come into contact with moisture and warmth to produce carbon dioxide bubbles. These bubbles expand during the cooking process to caused the baked item to rise, producing a fine, delicate result (cakes).

Bicarbonate of soda can be used successfully as a raising agent; however, it has a yellow appearance and a strong, unpleasant taste. It must therefore be combined with other strong flavours to disguise this, eg chocolate cake and gingerbread.
Biological Raising Agent
Yeast is a living organism that needs warmth, liquid, food and time to release carbon dioxide. This process is called fermentation and aerates the dough during bread making.

A biological raising agent is added which produces a CO2 gas. The carbon dioxide is activated during bread production when yeast is combined with heat in a warm moist condition. When the fermented yeast is added to the flour and warm liquid it increases in size. This is known as the proving stage.
Key Questions
Name the 3 main raising agents discussed today?

Explain how raising agents work?

What is the difference between a chemical and a biological raising agent?
Mechanical Methods
Manually incorporating air into food products using different techniques.

Processes include:
Sieving, rubbing in fat, whisking, beating, rolling, creaming fat and sugar
Full transcript