Aims • To be aware that there are different types of raising agent. • To understand how the raising agents work. • To use different raising agents in a variety of dishes.
Raising agents • Steam • Air • Carbon Dioxide -Chemical – bicarbonate of soda -Biological - Yeast
Steam • For steam to make a mixture rise it needs to have • A high proportion of liquid in mixture • A high baking temperature • As liquid reaches boiling point steam is given off. Steam forces way up through mixture to stretch and raise it. The mixture cooks and sets in the risen shape. • Foods that are raised mainly by steam have a very open and uneven texture eg Yorkshire puddings, choux pastry • Steam can be combined with other raising agents egAir + CO2 in cakes, bread and pastry
Air • Is incorporated into mixtures using mechanical methods • Sieving flour (cakes, pastry, batter) • Creaming together fat and sugar (cakes, biscuits) • Rubbing fat into flour (shortcrust pastry, scones) • Whisking egg white (meringue, whisked cakes) • Beating mixtures (batters, choux pastry) • Rolling and folding (flaky pastry, rich yeast pastries)
Bicarbonate of Soda • Also known as baking soda or sodium bicarbonate, bicarbonate of soda is used as a leavening agent for a variety of baked goods, such as scones, cakes, puddings, biscuits and batters. It is usually used with and acid ingredient such as cream of tartar, buttermilk or orange juice. The white powder is activated as soon as it is mixed with an acidic liquid, releasing carbon dioxide gas that causes the baked item to rise. • Bicarbonate of soda can last for up to 3 years in a cool dry place. However, if it is allowed to get warm or damp, the soda will start to react, thus adversely affecting its effectiveness.
Cream of Tartar • Cream of tartar is a fine white powder that is extracted from the tartaric acid that crystallises in wine casks during the fermentation of the grapes. • It may be combined with bicarbonate of soda to produce baking powder, which is added to cake and scone mixtures to help them rise. • A pinch of cream of tartar can also help to increase the volume and stability of whisked egg whites, before they are made into meringues or folded into cake batters.
Baking Powder • Baking powder is used as a leavening agent for a range of doughs and batters for items such as cakes, puddings, scones and biscuits. It is made from a combination of alkaline and acid substances (usually bicarbonate of soda and cream of tartar) that react when they come into contact with moisture and warmth to produce carbon dioxide bubbles. These bubbles expand during the cooking process to cause the baked item to rise, producing a fine, delicate-textured result.
Self Raising Flour • Self-raising flour is white flour that is sold premixed with chemical leavening agents. Self-raising flour is composed of the following plain flour with baking powder added.
Yeast • Yeast is a single-cell fungus that feeds on simple sugars to produce carbon dioxide and alcohol. It is used to ferment grains and fruits to make wine, beer and spirits, and as a leavening agent to make a range of breads and baked products. Baker's yeast may be used to make a variety of breads, rolls, cakes and sweet dough mixtures. • When the yeast is added to a mixture of dough, a fermentation process begins as the yeast feeds on the sugars and produces carbon dioxide gas, which causes the dough to rise