How is gas introduced into a mixture so that baked goods rise?
Raising agents: chemical (baking powder, bicarbonate of soda), biological (yeast), mechanical (whisking, creaming, sieving, lamination) and steam, the gas each produces and how it makes a mixture rise, with food examples.
A focused answer on raising agents for Eduqas GCSE Food Preparation and Nutrition (C560), covering chemical (baking powder, bicarbonate of soda), biological (yeast), mechanical and steam raising agents, the gas each produces, and how it makes cakes, breads and pastries rise.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this dot point is asking
Eduqas wants you to know the four kinds of raising agent (chemical, biological, mechanical and steam), the gas each one adds to a mixture, the conditions it needs, and how the gas makes baked goods rise. Always link the gas to a food example.
Chemical raising agents
The carbon dioxide forms bubbles that expand on baking and lift the mixture, while the heat sets the structure around them, giving a light cake, scone or soda bread. Too much raising agent makes a mixture rise too fast and then collapse.
Biological raising (yeast)
The carbon dioxide is trapped by the elastic gluten network in the dough, so the dough rises (proving). During baking the gas expands, then the heat kills the yeast and sets the gluten and starch, fixing the risen, open texture of the loaf; the alcohol evaporates. Yeast is slow, which is why bread needs proving time.
Mechanical and steam
Mechanical methods physically beat air into a mixture: whisking egg and sugar for a fatless sponge, creaming fat and sugar for a cake, sieving flour, folding, and rolling and folding fat into pastry (lamination) for flaky and puff pastry. The trapped air expands on heating to help the food rise.
How the gas raises the food
Whatever the raising agent, the principle is the same: a gas (carbon dioxide, air or steam) is introduced and held in the mixture, then heat makes the gas expand, and the structure sets (gluten and starch in dough, coagulated egg in a sponge) around the bubbles to fix the light, risen texture.
Try this
Q1. Name the gas that makes bread rise. [1 mark]
- Cue. Carbon dioxide (from yeast fermentation).
Q2. Name the raising agent that makes choux pastry rise. [1 mark]
- Cue. Steam (the high water content turns to steam on strong heating).
Exam-style practice questions
Practice questions written in the style of WJEC Eduqas exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Eduqas 20186 marksExplain how yeast acts as a raising agent in bread, including the conditions it needs and the gas it produces.Show worked answer →
A 6-mark extended-response question on biological raising.
Yeast is a living, single-celled fungus used to raise bread. Given warmth, moisture, food (sugar or the starch in flour) and time, the yeast respires and ferments the sugar, producing carbon dioxide gas and a little alcohol. This is fermentation.
The carbon dioxide is trapped by the elastic gluten network in the dough, so the dough stretches and rises (proving). During baking, the gas expands further and then the heat kills the yeast and sets the gluten and starch, fixing the risen, open structure of the loaf. The alcohol evaporates.
Top-band answers (5 to 6 marks) name carbon dioxide from fermentation, the conditions yeast needs (warmth, moisture, food, time), and that the gluten traps the gas so the bread rises and then sets on baking.
Eduqas 20214 marksName the gas produced by baking powder and explain how it makes a cake rise.Show worked answer →
A 4-mark structured question on chemical raising.
Baking powder is a chemical raising agent, a mixture of an alkali (bicarbonate of soda) and an acid (such as cream of tartar). When it is mixed with liquid and heated, the acid and alkali react to produce carbon dioxide gas.
The carbon dioxide forms bubbles in the cake mixture; on baking the gas expands and lifts the mixture, while the heat sets the structure around the bubbles, giving a light, risen cake. Too much baking powder makes the cake rise too fast and then sink.
Markers reward naming carbon dioxide, explaining the acid-alkali reaction on heating, and that the gas expands and the mixture sets around it.
Related dot points
- The functional and chemical properties of protein: denaturation, coagulation, foam formation (aeration of egg) and gluten formation, with food examples and the conditions that cause each.
A focused answer on the functional and chemical properties of protein for Eduqas GCSE Food Preparation and Nutrition (C560), covering denaturation, coagulation, foam formation and gluten formation, the conditions that cause them, and their food examples.
- The functional and chemical properties of carbohydrate: gelatinisation of starch, dextrinisation, caramelisation and the use of sugar and starch in cooking, with the conditions that cause each and food examples.
A focused answer on the functional and chemical properties of carbohydrate for Eduqas GCSE Food Preparation and Nutrition (C560), covering gelatinisation of starch, dextrinisation and caramelisation, the conditions that cause each, and their food examples in sauces, baking and sweets.
- The functional properties of fats and oils: shortening, aeration and plasticity, and emulsification, with the conditions that cause each, the role of emulsifiers such as egg yolk lecithin, and food examples.
A focused answer on the functional properties of fats and oils for Eduqas GCSE Food Preparation and Nutrition (C560), covering shortening, aeration and plasticity, and emulsification, the role of emulsifiers such as egg yolk lecithin, and food examples in pastry, cakes and sauces.
- Why food is cooked (safety, digestibility, palatability, variety and shelf life) and the three methods of heat transfer into food: conduction, convection and radiation, each linked to cooking methods.
A focused answer on why food is cooked and how heat is transferred for Eduqas GCSE Food Preparation and Nutrition (C560), covering the reasons for cooking (safety, digestibility, palatability, variety, shelf life) and conduction, convection and radiation with cooking examples.
- Cereals as a commodity group: wheat, rice, oats, maize and the products made from them (bread, flour, pasta), their nutritional value, working characteristics, and how they are grown, processed and stored.
A focused answer on cereals as a commodity group for Eduqas GCSE Food Preparation and Nutrition (C560), covering wheat, rice, oats and maize, the products made from them, their nutritional value, working characteristics in cooking, and how they are processed and stored.
Sources & how we know this
- WJEC Eduqas GCSE Food Preparation and Nutrition specification (C560) — WJEC Eduqas (2016)