Most of us eat an assortment of flour based foods, for example breads, cakes, pastries and batters in various forms. In order to make these foods palatable and light in texture a gas must be introduced during the baking process. The gas expands when heated and in cooking they are capable of raising a mixture.

As a mixture rises the starches stretch and the protein sets, or coagulates, forming a structure. Too little gas and there will be insufficient rising and if there is too much gas it will expand too quickly, escape and the structure collapses. It is important for the mixture to have the correct consistency and proportion of raising agent. Measure carefully!


Yeast is a microscopic living plant and must be used carefully. In order for yeast to work successfully as a raising agent, certain conditions must be met. It must have food, correct warmth and liquid. Once all this criteria has been met the yeast will produce CO2 gas during a chemical reaction called fermentation.

The correct conditions for fermentation to happen are:

Food: sugar or flour

Correct warmth: between 25 – 29 degrees C. Any higher will kill the yeast and lower will reduce its activity to the point where it is alive but inactive.

Moisture: at the above temperature. If you feel the liquid, it should feel neither warm nor cold.

Examples of use of yeast are: breads, blini’s and some pastries

Baking Powder

When we bake cakes it is usual to use commercially produced Self Raising flour. This is soft cake flour with baking powder already added to it. It is not suitable for:

Scones – too weak- recipes include extra baking powder

Rich cakes – too much raising agent, so plain flour is used

Bread, pastries, biscuits – chemical raising agents aren’t required though air is incorporated during the baking process.

Scones: 4-5tsp to 450g plain flour Suet pastry: 4-5tsp to 450g plain flour


Half fat to quantity of flour: 4tsp to 450g plain flour

Three quarters fat to quantity of flour: 3tsp to 450g plain flour

Equal fat to quantity of flour: 2tsp to 450g plain flour