See the idea. Put it to the test.

Find a practical

1. Science and Technology K–6 · Year 3

   Is yeast alive? Sugar, warm water and a balloon

   A living thing takes in food and gives off waste, so a packet of dry yeast that inflates a balloon when fed sugar shows a characteristic of life that flour does not.

   PracticalLow risk

2. Science 7–10 · Year 8

   Yeast respiration: carbon dioxide output against temperature

   Living cells release carbon dioxide as they respire sugar, and the rate depends on temperature.

   PracticalLow risk

3. Technologies K–10 · Years 1–2

   From cream to butter: a dairy food made by shaking

   Cream from cows' milk turns into butter when hard shaking makes its fat droplets join together and separate from the liquid buttermilk.

   PracticalMedium risk

4. Technologies K–10 · Years 3–4

   From wheat grain to flour: milling by hand

   Milling breaks wheat grains into flour, and sieving separates the brown bran from the white endosperm flour, while the total mass stays the same apart from dust that escapes.

   PracticalLow risk

5. Technologies K–10 · Years 5–6

   Why bread dough rises: yeast and temperature

   Yeast ferments sugar in dough and gives off carbon dioxide that makes the dough rise, and it works faster in warm conditions, which is why bakers prove dough somewhere warm.

   PracticalMedium risk

6. Agriculture and Food 7–12 · Years 7–8

   Bicarbonate of soda as a raising agent: gas from heat and from acid

   Sodium hydrogencarbonate (bicarbonate of soda) works as a raising agent because it produces carbon dioxide gas when it is heated or mixed with an acid; the gas turns limewater milky, a sign that a new substance has formed, and the mixture loses mass as the gas escapes.

   PracticalMedium risk

7. Agriculture and Food 7–12 · Years 7–8

   Checking a food thermometer and the temperature danger zone

   Food-poisoning bacteria can multiply between 5 °C and 60 °C, so potentially hazardous food is kept at 5 °C or colder or at 60 °C or hotter, checked with a probe thermometer proven in an ice slurry.

   PracticalLow risk

8. Agriculture and Food 7–12 · Years 7–8

   Why cut apple turns brown, and how acid dips and blanching stop it

   Cutting fruit lets an enzyme (polyphenol oxidase) use oxygen to turn natural phenolic compounds into brown pigments, so acid and antioxidant dips, cold, or heat that denatures the enzyme slow or stop the browning.

   PracticalLow risk

9. Agriculture and Food 7–12 · Years 7–8

   Yeast and the rise of bread dough at 20, 30 and 37 °C

   Yeast ferments sugar to carbon dioxide, and the gas trapped by gluten makes dough rise faster in warm conditions than in cool ones.

   PracticalLow risk

10. Agriculture and Food 7–12 · Years 9–10

    Blanching and enzymes: a catalase test on raw and blanched vegetables

    Enzymes in raw vegetables keep working after harvest and in the freezer, and blanching in boiling water denatures them, which a catalase test with hydrogen peroxide makes visible.

    PracticalMedium risk

11. Agriculture and Food 7–12 · Years 9–10

    Cooling cooked rice safely: the two-stage cooling rule

    Cooked rice is a potentially hazardous food, so it must cool from 60 °C to 21 °C within 2 hours and from 21 °C to 5 °C within a further 4 hours, and a shallow tray cools far faster than a deep pot.

    Practical, model not builtLow risk

12. Agriculture and Food 7–12 · Years 9–10

    Emulsifiers: keeping oil and vinegar mixed

    Oil and water separate into layers after shaking, but an emulsifier such as egg yolk or mustard keeps oil droplets dispersed so the mixture stays uniform.

    PracticalLow risk

13. Agriculture and Food 7–12 · Years 9–10

    Washing out gluten from bread, plain and cake flours

    Wheat flour proteins (glutenins and gliadins) join into an elastic gluten network when wetted and kneaded, and how much gluten a flour forms depends on its protein content.

    PracticalLow risk

14. Agriculture and Food 7–12 · Years 11–12

    Coagulating milk protein with rennet enzymes and with acid

    Milk proteins coagulate into curd when enzymes such as chymosin act on casein at about 37 °C or when acid is added, the functional property behind cheese making, and temperature changes the rate.

    PracticalLow risk

15. Agriculture and Food 7–12 · Years 11–12

    Ethanol from sugar: following fermentation by mass loss

    Yeast ferments glucose to ethanol and carbon dioxide in a fixed ratio, so the mass of carbon dioxide lost from a fermenting flask tells how much ethanol, a biofuel, has been made.

    Practical, model not builtLow risk

16. Agriculture and Food 7–12 · Years 11–12

    Gelation and protease enzymes: fresh and canned pineapple in jelly

    Gelatine sets because its protein chains form a network that traps water, and protein-digesting enzymes in fresh pineapple and kiwi fruit cut those chains so the jelly stays liquid unless heat has denatured the enzymes.

    PracticalLow risk

17. Agriculture and Food 7–12 · Years 11–12

    Jam and jelly setting point: sugar, pectin, acid and temperature

    Jam sets when enough water has boiled off for sugar, pectin and acid to form a gel, which happens at 8 °F (4.4 °C) above the local boiling point of water, so the setting temperature falls with altitude.

    Practical, model not builtMedium risk

18. Agriculture and Food 7–12 · Years 11–12

    Preserving apple by drying: mass loss and pretreatment

    Drying preserves food by removing the water that microbes and enzymes need, and weighing slices as they dry shows how much of fresh fruit is water.

    Practical, model not builtLow risk