3.3.2.5.1 Chemical raising agents Quiz: AQA Food Preparation and Nutrition, Unit 2

The 20 questions

1. Which raising agent is a mixture of bicarbonate of soda and an acid?

   • Whisked egg white
   • Baking powder
   • Dried yeast
   • Plain flour

2. What gas do chemical raising agents produce in a mixture?

   • Oxygen
   • Nitrogen
   • Carbon dioxide
   • Hydrogen

3. A cake recipe uses self-raising flour and no baking powder. What is already in the flour?

   • A chemical raising agent, usually baking powder, mixed in by the manufacturer
   • Gluten that has been pre-kneaded into the flour to give structure
   • Whisked air that has been sieved into the flour during milling
   • Dried yeast that has been ground into the flour for an even rise

4. Why does bicarbonate of soda need an acid to work well in a recipe?

   • Without an acid it dissolves the starch and turns the mixture into a thin syrup
   • Without an acid it denatures the protein and sets the cake too firm
   • Without an acid it caramelises the flour and makes the cake bitter
   • Without an acid it cannot release carbon dioxide well and leaves a soapy taste

5. Buttermilk is used with bicarbonate of soda in a scone recipe. Why?

   • Buttermilk is acidic and reacts with the bicarbonate to release carbon dioxide
   • Buttermilk is starchy and gelatinises when it is mixed with the bicarbonate
   • Buttermilk is fatty and emulsifies the bicarbonate into the dough evenly
   • Buttermilk is sweet and caramelises with the bicarbonate to brown the crust during baking

6. When is the carbon dioxide from baking powder released?

   • When the flour is sieved before the eggs are added to the bowl
   • Only when the mixture is frozen for a long time before baking
   • When the mixture is moistened and then heated in the oven
   • Only when the mixture is kneaded for several minutes by hand

7. A scone has too much baking powder and tastes bitter. Why?

   • Excess fat has emulsified and separated out to form an oily layer
   • Excess raising agent leaves an unreacted, soapy or bitter residue in the crumb
   • Excess sugar has caramelised and burned in the oven during baking
   • Excess starch has gelatinised and tastes raw and chalky to the palate

8. Why should baking powder be stored in a dry place?

   • Moisture in the air caramelises the powder and turns it brown in the tin
   • Moisture in the air can start the reaction early, so its raising power is lost
   • Moisture in the air gelatinises the powder into a firm, lumpy mass
   • Moisture in the air denatures its protein, so it no longer releases gas

9. A recipe doubles the bicarbonate of soda but not the acid in a sponge. What is the likely result?

   • The sponge caramelises more, because excess bicarbonate speeds browning of sugar
   • The sponge becomes more elastic, because excess bicarbonate strengthens gluten
   • The sponge tastes soapy and may turn yellow because excess alkali is unreacted
   • The sponge rises less, because excess bicarbonate denatures the egg protein

10. Which raising agent is classed as chemical rather than biological?

    • Brewer's yeast
    • Bicarbonate of soda
    • Lactobacillus culture
    • Sourdough starter

11. Why is baking powder described as double-acting?

    • It stops the mixture setting, so the cake stays soft and wet inside
    • It releases some gas when wet and more gas when heated in the oven
    • It emulsifies the fat, so the cake keeps its shape while it cools
    • It caramelises the sugar on contact, so the cake browns evenly on top

12. A cook uses 2 teaspoons of baking powder for 200g of flour. What is the purpose of the measured amount?

    • To emulsify the fat so that the cake stays moist for several days after baking
    • To release enough gas for lift without leaving a bitter or soapy taste
    • To caramelise the flour sugars fully during the baking process
    • To denature the flour protein so that the cake sets firm and dry

13. Which statement describes the reaction in baking powder?

    • Bicarbonate of soda reacts with an acid in the presence of moisture to produce carbon dioxide
    • Starch in the flour reacts with oxygen to produce a gas that lifts the mix
    • Protein in the eggs reacts with fat to produce a foam that rises in the tin
    • Sugar in the mix reacts with heat to produce steam that lifts the dough

14. Why does too much acid in a scone mix make the scone taste sour?

    • The excess acid has caramelised the sugar in the mix, and the caramel gives a sour flavour
    • The excess acid has gelatinised the starch and turned the surface of the scone sour and sticky
    • The excess acid is left unreacted because there is not enough bicarbonate to neutralise it
    • The excess acid has denatured the flour protein and released sour compounds into the crumb

15. What happens to baking powder once a cake is in a hot oven?

    • It turns into solid sugar, which hardens the crumb around the air cells as it cools
    • It continues to release carbon dioxide, which expands the mixture as it sets
    • It emulsifies with the fat and separates to leave an oily top layer
    • It melts into a syrup which then evaporates to leave a dry crust

16. Why are bicarbonate-raised scones best baked soon after mixing?

    • The reaction needs air, so the scone must be whisked to start it working
    • The reaction starts once the mix is moist, so gas escapes if the dough waits
    • The reaction needs cold conditions, so the scone must be baked as soon as it is mixed
    • The reaction stops once the mix is moist, so the scone sets before it rises

17. Which pair of ingredients forms a chemical raising agent system?

    • Bicarbonate of soda and cream of tartar
    • Bicarbonate of soda and caster sugar
    • Cream of tartar and plain flour
    • Whisked egg white and icing sugar

18. Which statement about chemical raising agents is correct?

    • They work by denaturing the fat so that air is trapped inside the mixture
    • They are added as powders or are already in self-raising flour, and react with moisture and heat
    • They rely on live microorganisms that must be fed sugar before the cake is baked
    • They only work in cold mixtures and are added after the cake has been baked

19. What does sieving baking powder into the flour achieve?

    • It spreads the raising agent evenly so the rise is uniform
    • It gelatinises the raising agent into a sticky paste before mixing
    • It denatures the raising agent so that it stops releasing gas
    • It melts the raising agent so that it dissolves into the fat

20. Why are chemical raising agents useful in quick breads?

    • They produce gas only after proving for several hours in a warm place
    • They produce gas without needing yeast to ferment or time to prove
    • They produce steam only when the mixture is kneaded for several minutes
    • They produce alcohol which evaporates in the oven to lift the mixture

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