3.4.1.2 Signs of food spoilage: enzymic action, mould and yeast Quiz: AQA Food Preparation and Nutrition, Unit 3

The 20 questions

1. What is a typical sign of enzymic action in a ripening banana?

   • A sharp smell of vinegar as the fruit ferments in the bowl
   • Fat rising to the surface of the banana as it is cut open
   • Foaming of the flesh as its protein denatures on the counter
   • Browning and softening of the skin and flesh as the fruit ripens

2. What does mould growth on food usually look like?

   • A glossy, smooth layer of fat spread across the surface
   • A dry, crisp, golden surface like a baked crust on the top
   • A clear liquid pooled beneath a firm, set gel in the dish
   • Fuzzy patches of threads, often in white, green or blue

3. Which foods are commonly affected by mould growth?

   • Dried pasta stored in a sealed packet
   • Sugar kept in a closed jar on a shelf
   • Plain flour kept in a sealed tin
   • Bread and cheese

4. Which yeast action is visible in grapes that have been left out?

   • Hardening of the flesh into a firm, gel-like mass throughout the fruit
   • A dry, crisp skin that splits into hard, brittle flakes on the surface
   • Bubbling, a sour or alcoholic smell, and a fizzy, fermented taste
   • Browning of the flesh as sugars caramelise on contact with the air

5. A jar of fruit has a fizzy top and a sour smell. What should be done?

   • Leave it open for a day so that the sour smell can be dispersed
   • Skim off the top and eat the rest, since the fizz is harmless
   • Heat it briefly to set the fruit into a firm and safe jelly
   • Discard it, because yeast fermentation has spoiled the fruit

6. Which sign would show mould rather than yeast in a food?

   • Furry threads visible on the surface
   • A sharp alcoholic smell coming from the open jar
   • A fizzing sound when the lid of the container is opened
   • Bubbles rising through the liquid of the food

7. A cut melon is left out and becomes slimy and sour. Which spoilage is most likely?

   • Yeast action on the sugars in the moist flesh
   • Protein coagulation across the flesh as it stands on the counter
   • Fat emulsification that separates the melon into distinct layers
   • Starch gelatinisation that makes the flesh thick and gluey

8. What is a common sign of enzymic browning in cut apples?

   • Bubbles forming in the flesh as the apple ferments slowly
   • Brown colour spreading across the cut flesh
   • Dry, cracked skin forming on the outside of the apple
   • A white, fuzzy coat growing over the cut surface of the apple

9. How should bread be stored to prevent mould growth?

   • In the fridge at 2°C without any wrapping around the loaf at all
   • In a sealed, damp container kept in a warm place in the kitchen
   • In a dry bin or bag at room temperature, and used quickly
   • Uncovered in a humid kitchen for several days before it is eaten

10. Which of these foods is named in the spec as showing yeast action?

    • Dried pasta stored in a sealed packet on a dry cupboard shelf for several months
    • Strawberries
    • Plain flour
    • Cured ham

11. A tomato sauce develops a sour smell and tiny bubbles. Which spoilage is most likely?

    • Protein denaturation making the sauce set firm in the pan
    • Caramelisation of the tomato sugars in the pan over heat
    • Yeast action fermenting the sugars in the sauce
    • Mould growth in a dense, dry layer on the surface

12. Which is the best way to reduce mould risk on fresh fruit at home?

    • Leave the fruit wet in a sealed container at room temperature
    • Keep the fruit in a damp bag at room temperature for several days
    • Store the fruit uncovered in warm sunshine to dry the surface
    • Wash, dry and chill the fruit promptly, and use it quickly

13. Why are bruised or cut fruits more prone to yeast action?

    • Damage releases juices and sugars that yeast can ferment readily
    • Damage denatures the fruit protein, which stops yeast from growing
    • Damage makes the fruit too dry for yeast to grow in its flesh
    • Damage removes all the water from the fruit so yeast cannot ferment

14. Which spoilage sign would show in a jar of jam kept too long?

    • A glossy layer of fat set firm across the top of the jam
    • A visible fuzzy patch or a fizzing, sour smell
    • A clear layer of gel pooled at the bottom of the jar
    • Dry, crisp edges with a golden crust forming around the jar

15. Why is enzymic action in a fruit described as spoilage even before any mould appears?

    • Enzymes change the colour, texture and flavour as the fruit breaks down
    • Enzymes set the fruit into a dry, crisp coat that prevents it being eaten
    • Enzymes remove all of the vitamin content of the fruit at a single point
    • Enzymes make the fruit too sweet to eat without caramelising it first

16. A baker finds a loaf with a green-blue fuzzy patch. What should be done?

    • Cut the patch off and eat the rest of the loaf without any concern
    • Discard the whole loaf, because mould roots can spread beyond the visible patch
    • Leave it in a warm place so that the mould dries out and disappears
    • Toast the loaf to kill the mould and then serve it fresh to the guests

17. Vegetables are prepared a day early and left in a warm kitchen. Which spoilage risk do they face?

    • Enzymic action and yeast or mould growth on moist, cut surfaces
    • Caramelisation of the vegetables into a crisp, brown crust on the surface
    • Gelatinisation of the vegetables into a thick, glossy sauce on the board
    • Emulsification of the vegetable water into a stable cream on the board

18. Which sign distinguishes enzymic spoilage in a pear from mould?

    • A glossy fat layer forming on the cut surface of the pear
    • Brown colour and soft texture spreading through the flesh, without fuzzy growth
    • Bubbles rising and a sour smell coming from the flesh of the pear
    • Fuzzy threads of mould growing across the skin in patches over the pear

19. Why do moulds form visible growth on food but bacteria often do not?

    • Bacteria only grow in the dark, while moulds need bright light to grow
    • Moulds grow as multicellular threads, while most bacteria are too small to see
    • Bacteria are dissolved in water, while moulds stay solid on the surface
    • Bacteria produce a gas, while moulds produce a liquid that stays hidden

20. Which factor does most to encourage mould growth in a fruit preserve?

    • Very low temperatures and dry air, stored in a freezer for months
    • High sugar and a sealed lid, kept in a cool, dark cupboard
    • Moisture and warmth in the jar, with the lid left loose
    • Acidity and a tight lid, stored in a fridge at low temperature

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