Raising agents

We use raising agents to add gas to dough and other mixtures so they can expand and rise when heated.

Bicarbonate of soda, when heated breaks down to produce carbon dioxide bubbles that expand to make your mixture rise. It tends to be used with foods with strong flavours such as chocolate cake and gingerbread as it has an alkaline soapy flavour. Baking powder is a mixture of bicarbonate of soda which is an alkali and cream of tartar which is an acid. A neutralisation reaction takes place when baking powder is heated which gets rid of the soapy taste. Self-raising flour contains a mixture of plain flour and baking powder.

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Yeast is a biological raising agent used in bread dough, it is a microorganism that causes fermentation which is a process that releases alcohol and carbon dioxide. Yeast dough is usually proved (left in a warm place to allow time for the fermentation to take place).  This is when the carbon dioxide is released and trapped in the dough, causing it to rise. During the baking process the yeast is killed by the heat which stops the fermentation. The baking process allows the carbon dioxide to expand which causes the bread to rise even more. All the alcohol produced by the yeast evaporates during this process.

When you cook mixtures which contain a lot of liquids such as puff and choux pastry and batters, water leaves the mixture as steam. The steam is created in your hot oven and the steam rising causes the mixture to raise up. As the water leaves your mixture your food bakes to become solid.

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We also add air to mixtures to make them raise. Air can be folded into dough and mixtures. When making a cake mixture you use a spatula or spoon to repeatedly poor the liquid mixture over itself trapping the air into your mixture. Pastry doughs can be folded into layers, trapping air in between the layers each time you fold the mixture.

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Beating is when you use a spoon of fork to mix ingredients together quickly driving air into your mixture. Whisking uses the same method as beating only you use a whisk. When you sieve flour, the air becomes trapped between the individual flour particles. We also add air into our mixtures by creaming. Creaming is the process of mixing butter and sugar together and between flour particles when you add fat.