3.4.1.1.1 Growth conditions for microorganisms and enzymes Quiz: AQA Food Preparation and Nutrition, Unit 3

The 20 questions

1. Which conditions affect the growth of micro-organisms in food?

   • Price, country of origin, brand name and shop location
   • Colour, shape, size and weight of the food
   • Sound, light, packaging and the design of the label
   • Temperature, moisture, food and time

2. What are bacteria, yeasts and moulds collectively called in food science?

   • Micro-organisms
   • Proteins
   • Vitamins
   • Enzymes

3. Enzymes are biological catalysts. What are they usually made from?

   • Sugar
   • Fat
   • Protein
   • Starch, which is a carbohydrate that gelatinises when it is heated in a sauce or a stock

4. Which conditions would help bacteria grow in cooked rice left at room temperature?

   • Boiling water with a high concentration of salt and sugar
   • Freezing temperature, dry air and no food available nearby
   • Warm temperature and moisture, with plenty of food and time
   • Very high acidity, with no moisture and no oxygen in the pan

5. What is the main effect of keeping food below 5°C?

   • It stops enzymes from being present in the food at all
   • It slows the growth of most bacteria, though it does not kill them
   • It causes the food to caramelise slowly while it is stored
   • It kills all bacteria so the food is completely safe to eat

6. Which factor could help control micro-organism growth in a jam?

   • Oxygen increased through a loose lid on the jar at all times
   • Fat added to the jam to coat the fruit in a thin layer
   • A temperature raised above boiling point during the storage period
   • Water availability reduced by a high sugar content

7. What is water availability in food safety?

   • The amount of free water that micro-organisms can use to grow
   • The amount of water that is frozen solid inside the food
   • The temperature at which water in an open pan starts to boil and turn into steam at sea level
   • The rate at which water is lost from a food during drying

8. Why does pH matter for micro-organism growth?

   • pH controls the setting temperature of protein, not the micro-organisms in it
   • Many food-poisoning bacteria grow poorly in acid, so acidic foods resist growth
   • Many food-poisoning bacteria grow best in very strong acid, which speeds growth
   • pH only affects the flavour of food and has no effect on micro-organisms

9. What is pH?

   • A scale from 0 to 100 measuring the fat content of a food
   • A scale from 1 to 5 measuring how much heat a food has absorbed
   • A scale from 0 to 14, where values below 7 are acidic
   • A scale from 0 to 10 measuring how sweet a food tastes

10. How does time affect food spoilage?

    • Micro-organisms are destroyed by time passing inside the food
    • Enzymes are destroyed as food gets older, so spoilage then stops
    • Micro-organisms multiply repeatedly, so long periods allow large growth
    • Time causes food to caramelise slowly, which prevents micro-organisms from growing on its surface

11. Enzymes in fruit stay active after harvest. Which storage condition slows their action most?

    • Cold storage at a low temperature
    • Warm storage at a high humidity level
    • Storage with a heavy weight placed on top
    • Exposure to bright light for several days

12. Which description of a yeast is correct?

    • A mineral that makes dough rise by setting firm in the heat of the oven
    • A single-celled fungus that ferments the sugars in dough and fruit
    • A protein that denatures in acid and forms a firm gel in the mixture
    • A fat that melts in the oven and lifts the mixture as it heats through

13. Why do foods high in protein and moisture support micro-organism growth more than dry foods?

    • They freeze the micro-organisms, which slows their reproduction
    • They raise the acidity, which speeds up micro-organism growth
    • They destroy the enzymes, which then stops the micro-organisms feeding
    • They supply the nutrients and water that micro-organisms need

14. What is a mould that grows as visible threads on bread?

    • A starch granule
    • A mould
    • An enzyme
    • A vitamin

15. What happens to enzymes when they are heated to about 70°C or above?

    • They multiply rapidly and speed up the ripening of the food
    • They dissolve completely into the fat and are removed from the food
    • Their structure denatures, so they lose their ability to act as catalysts
    • Their structure becomes stronger and their activity increases in the food

16. Why are micro-organisms harmful to food in general terms?

    • They multiply and produce changes that spoil food or cause food poisoning
    • They make food sweet and caramelised as they grow in the product
    • They dissolve the starch, so the food becomes thin and runny
    • They set the proteins in the food, so it becomes firm and dry

17. Which measure lowers the water availability in a cured meat?

    • Wrapping it in cling film and leaving it at room temperature
    • Adding sugar and boiling it in a large volume of water
    • Adding salt and drying the meat
    • Heating it to 75°C and then cooling it quickly in a bowl

18. Which conditions suit mould growth on bread most?

    • Boiling temperatures and a pH close to 1 in an open container
    • Very low moisture and a high salt content, sealed in a tin
    • Freezing temperatures, dry air and bread stored in an open bag
    • Warm, humid conditions, with the bread wrapped and left unchilled for days

19. What is the role of oxygen for most moulds?

    • Moulds are killed by oxygen, so open packs stay free of mould
    • Most moulds need oxygen to grow, so sealed packs slow their growth
    • Moulds need oxygen only to freeze, so air speeds their freezing in the freezer
    • Oxygen denatures moulds, so they cannot grow in any pack at all

20. Why does a food left at 20°C for four hours carry a risk?

    • Micro-organisms are fully killed by the warmth, so the food is safe
    • Enzymes are completely destroyed, so the food stays fresh and safe
    • Bacteria may multiply to harmful numbers during that time
    • The food sets firm as its proteins coagulate fully at this temperature

Related quizzes

• High risk foods and control of microorganism growth Quiz · 3.4.1.1.2 · 20 questions
• Control of enzymic action in food Quiz · 3.4.1.1.3 · 20 questions
• Signs of food spoilage: enzymic action, mould and yeast Quiz · 3.4.1.2 · 20 questions
• Microorganisms in food production Quiz · 3.4.1.3 · 20 questions
• Sources of bacterial contamination Quiz · 3.4.1.4.1 · 20 questions
• Main food poisoning bacteria Quiz · 3.4.1.4.2 · 20 questions
• Control and general symptoms of food poisoning Quiz · 3.4.1.4.3 · 20 questions
• Buying and storing food safely Quiz · 3.4.2.1 · 20 questions
• Preparing, cooking and serving food safely Quiz · 3.4.2.2 · 20 questions
• Protein: biological value, complementation and alternatives Quiz · 3.2.1.1 · 20 questions