Four main raising agents are used in cooking:
- Air – egg whites, beating creaming, rubbing in
- Steam – profiteroles,choux pastry, Yorkshire pudding
- Carbon dioxide – yeast fermentation, baking powder, self raising flour
- Chemicals – bicarbonate of soda, baking powder
How do chemical raising agents work?
There are 3 main chemical raising agents:
- Sodium bicarbonate (bicarbonate of soda, E500 sodium carbonates) is a raising agent used in soda bread and gingerbread. It is an alkali.
- Cream of tartar is an acid called potassium hydrogen tartrate and it is mixed with bicarbonate of soda to provide the acid ingredient for baking powder. This ingredient can be added to stabilise whipped egg whites and increase their volume, and is added to whipped cream.
- Baking powder is made from the alkali, bicarbonate of soda and the acid, cream of tartar. As soon as liquid is added to the baking powder or bicarbonate of soda, carbon dioxide gas bubbles are given off which push up the cake, muffin or bread mixture. Baking powder has a drying agent mixed with it to stop it reacting in the packet.
Make your own baking powder: Mix 1 level teaspoon bicarbonate of soda and 2 level teaspoons cream of tartar.
Self raising flour is made from plain flour and baking powder.
Make your own self raising flour: Add 1 heaped teaspoon baking powder to 100 g plain flour.
The science bit
Bicarbonate of soda produces more carbon dioxide gas if it is mixed with an acid food – cream of tartar, buttermilk, sour milk. If you don’t mix it with an acid, you get a soapy taste in the food.
Experiment to blow up balloons.
Bicarbonate of soda
Cream of tartar
3 small DRY 500ml plastic water bottles
- Label the bottles 1,2,3.
- In 1 put 2 heaped teaspoons of bicarbonate of soda
- In 2 put 2 heaped teaspoons of baking powder
- In 3 put 2 level teaspoons of cream of tartar and 1 level teaspoon of bicarbonate of soda.
- Boil a kettle of water. Mix 300ml boiling water with 200 ml cold water.
- Pour 100ml of hot water into 1, quickly put a balloon on top and shake.
- Pour 100ml of hot water into 2, quickly put a balloon on top and shake.
- Pour 100ml of hot water into 3, quickly put a balloon on top and shake.
- Watch what happens. Which balloon is blown up the most?
Which one does not blow up?
Explain why the balloons either blow up or remain empty.
What can I cook?
Irish soda bread
80g self-raising flour
80g plain flour½ level tsp salt
½ level tsp bicarbonate of soda
100ml buttermilk or 100ml milk mixed with ½ teaspoon cream of tartar or vinegar
Preheat the oven to 200C/Gas 6. Lightly flour a baking sheet.
Put the flours, salt and bicarbonate of soda in a mixing bowl and stir.
Make a dent in the centre of the flour and pour in the buttermilk, or milk mixed with cream of tartar or vinegar. Mix quickly to form a soft dough.
Add less or more milk if the dough is not sticky enough.
Turn the dough onto a floured surface and knead.
Shape into a round and flatten the dough slightly before placing on the baking sheet.
Cut a cross on the top and bake for about 25 – 30 minutes or until the loaf sounds hollow when tapped. Cool on a wire rack.
What can I cook?
Cheese and onion muffins
75g margarine or butter
1 small onion (50g), very finely chopped
1 egg, beaten
150 g grated Cheddar cheese
100 g self raising flour
1 level teaspoon baking powder (2g)
2 tbs milk (30g)
Nutrition per portion
Energy 273 kcal, Protein 9.4g, Sugar 1 g, Fat 20g, Salt 0.9g
Allergens gluten, milk, egg
Preheat the oven to 200°C/Gas 6.
Melt the margarine or butter and stir in the chopped onion, beaten egg, 120g cheese – reserve the rest for the top.
Mix in the flour and baking powder to make a soft dough and add milk to soften the dough.
Place equal amounts into 6 muffin cases and bake 20-25 minutes until they are golden brown and spring back to touch.
Mixing bowl, muffin tray, teaspoon, measuring jug, chopping board, sharp knife, fork, grater, muffin cases