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.
NEA 1 Food Investigations 10 Tasks – Task 1 – Starchy ingredients to thicken sauces and soups Task 2 – Chemical raising agents for scones, cakes and biscuits Task 3 – Fats used in shortcrust pastry. Task 4 – Flours used in pastry – use for gluten tests Task 5 – Gluten in flour for breadmaking Task 6 – Gluten in flour for pasta making Task 7 – Sponge cakes – changing the flour Task 8 – Sponge cakes – changing the sugar Task 9 – Eggs as setting agents Task 10 – Egg foams and meringues