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Plant oils

Plant oils. Cooking with vegetable oils. Boiling point. Temperature depends on forces between molecules Bigger force = higher boiling temperature Molecules in veg. oils are much larger than water molecules Bigger forces Higher boiling point. What’s cooking?.

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Plant oils

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  1. Plant oils Cooking with vegetable oils

  2. Boiling point • Temperature depends on forces between molecules • Bigger force = higher boiling temperature • Molecules in veg. oils are much larger than water molecules • Bigger forces • Higher boiling point

  3. What’s cooking? • What happens to food when it cooks? • Heated to a high temperature • Chemical reactions occur • Causes a permanent change to food • Higher temperatures = different reactions • Food cooks differently

  4. How does the boiling point of vegetable oils differ from the boiling point of water? • Challenge question – why do the boiling point differ?

  5. Soak it up • Why can too much fried food be bad for you? • Food absorbs some of the oil it’s cooked in • Veg oils very high in energy • Increases the energy content of the food

  6. Why is food cooked in oil different from food cooked in water? • Challenge question – Explain why food cooked in oil may lead to weight problems

  7. Hydrogenated oils • Unsaturated oils are liquid at RToC • Double bond stops molecules fitting together well • Reduces the forces between molecules • Boiling point can be increased • Adding hydrogen, replacing double bonds • Molecules fit together better • Increased forces = higher boiling point

  8. Hydrogenated oils • Higher melting point – solid at RToC • “Hardening” of vegetable oils • Hydrogenated oils • Can be used to make spreads, margarine etc.

  9. What do we call it when we add hydrogen to vegetable oils, and what do we produce? • Challenge question – why is this done?

  10. Investigating oils • Compare the degree of saturation • Bromine can be used to test for saturation • Decolourised = unsaturated • Stays coloured = saturated • Which is the most saturated and which is least?

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