3.4.1.1.3 Control of enzymic action in food Quiz: AQA Food Preparation and Nutrition, Unit 3

The 20 questions

1. Why does freezing alone not stop enzyme action in vegetables?

   • Enzymes keep working slowly at freezer temperatures, so the food deteriorates
   • Enzymes are converted into fat when frozen and so no longer act on the food in the freezer
   • Enzymes dissolve into the ice and stop reacting for good in the pack
   • Enzymes become stronger when frozen and speed up dramatically in the food

2. Which acid is commonly used to slow browning in cut fruit?

   • Stearic acid from saturated fat
   • Benzoic acid as a preservative in drinks
   • Lactic acid from a cheese culture
   • Citric acid from lemon juice

3. Which control limits enzymic action by excluding oxygen?

   • Keeping cut food covered in water or in a sealed container
   • Keeping cut food uncovered on a hot bench for an hour
   • Whisking the cut food to incorporate air into the pieces before it is put into the serving bowl
   • Stirring the cut food in a warm sauce to heat it through

4. Which term describes slowing enzyme action by cooling food?

   • Emulsification
   • Refrigeration
   • Dextrinisation
   • Caramelisation

5. Why is a ripening banana kept at room temperature rather than in a fridge?

   • Cold denatures the banana starch, so the flesh becomes gluey and wet
   • Cold slows the enzymes that ripen it, so it would ripen very slowly
   • Cold speeds the enzymes that ripen it, so it ripens far too fast
   • Cold caramelises the banana sugars, so the skin turns brown instantly

6. What does a cut vegetable show when enzymic action has been left for a long time?

   • Fine white mould growing in threads across the cut surface
   • Colour change and loss of firmness as the cut surface reacts
   • Bubbles forming as the vegetable releases carbon dioxide gas
   • A sharp smell of vinegar as the vegetable ferments with yeast

7. A cook wants a cut pear to stay pale for a fruit salad served at lunch. Which steps work best together?

   • Heat it in a pan until caramelised and then serve it cold
   • Coat it in acid and keep it covered and chilled until serving
   • Leave it uncovered in a warm room and stir it with cream
   • Crush it into a paste and leave it open on the serving table so that it can be eaten later

8. Which of these is a control of enzymic action listed in the spec?

   • Use of sugar to sweeten the food before service
   • Use of acids to prevent enzymic browning
   • Use of fat to coat the surface of the food
   • Use of salt to season the food before cooking

9. Why are cut potatoes often placed in cold water before frying?

   • Water excludes air from the surface and slows enzymic browning
   • Water denatures the potato protein, which makes it easier to cut
   • Water dissolves the starch so that the chips become crisp when fried
   • Water caramelises the potato sugars, giving the chips a golden colour

10. Which action reduces the surface area that enzymes can reach?

    • Chopping the food into tiny dice and leaving it to stand
    • Cutting into larger pieces only when they are required
    • Mashing the food into a fine puree as soon as it is prepared
    • Grating the food and spreading it thinly over a board

11. Why is a fruit juice made from crushed fruit more likely to brown than the whole fruit?

    • Crushing cooks the fruit so the enzymes are concentrated in the juice
    • Crushing adds sugar, which caramelises and darkens the juice quickly
    • Crushing breaks cells and exposes more enzymes and flesh to oxygen
    • Crushing adds fat, which emulsifies and turns the juice cloudy and brown

12. A cook sprinkles vitamin C powder on sliced fruit. What does it do?

    • It gelatinises the fruit pectin and thickens the juice around the slices
    • It emulsifies the fruit oils so that the slices stay glossy and bright
    • It caramelises the fruit sugars into a brown, glossy glaze
    • It acts as an antioxidant that slows the browning reaction

13. Which of these is a physical control of enzyme action?

    • Adding lemon juice to the cut fruit
    • Chilling food in a fridge
    • Adding salt to the cooking water
    • Adding bicarbonate of soda to the water

14. What is the cause of the brown colour when a cut mushroom is left in air?

    • Enzymes reacting with oxygen once the cells are cut open
    • Protein coagulating into a grey film over the cut surface of the mushroom
    • Starch gelatinising inside the damaged cell walls of the mushroom
    • Sugar caramelising in the mushroom's natural juices on the surface

15. What does an antioxidant do in food?

    • It removes water from the food to dry the surface out completely
    • It slows reactions with oxygen, such as browning and vitamin loss
    • It speeds up reactions with oxygen to darken the food more quickly
    • It raises the pH and makes the food more alkaline and bitter

16. Which of these would speed up enzymic browning in cut fruit?

    • Adding lemon juice to the cut fruit before it is served
    • Whisking the cut fruit to incorporate extra air into the pieces
    • Chilling the cut fruit in a cold container before it is served to the guests at the buffet
    • Covering the cut fruit in a sealed bag in the fridge

17. Why does a warm temperature speed up enzyme action in food?

    • Higher temperature makes the enzymes dissolve into the fat and be removed from the food completely
    • Higher temperature turns the enzymes into sugars that are then used up
    • Higher temperature removes the protein from the enzyme and frees it
    • Higher temperature increases the rate at which molecules collide and react

18. What does a catalyst do in a food reaction?

    • It is used up completely in the reaction it speeds up in the food
    • It stops a reaction by absorbing the energy in the food being cooked
    • It changes the flavour of the food without affecting the reaction at all
    • It speeds up a reaction without being used up in it

19. A cook wants to slow enzymic action in bananas for a smoothie the next day. Which step helps most?

    • Dice them and leave them in a warm sink filled with plain water
    • Peel, cut and store them in acid-containing juice in a sealed container in the fridge
    • Peel, cut and leave them uncovered on the bench so that the air dries them
    • Mash them and leave them in a warm, sunny spot to allow ripening

20. Which factor does NOT slow enzymic browning in cut fruit?

    • Chilling the fruit in the fridge before it is cut
    • Covering the cut surface with a sealed film of plastic
    • Applying lemon juice to the cut surface of the fruit
    • Storage at a warm temperature in an open dish

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