C1.6 Plant oils and their uses

Many plants produce useful oils that can be converted into food products and fuels (e.g. biodiesel).
Candidates should use their skills, knowledge and understanding to:
■ evaluate the effects of using vegetable oils in foods and the impacts on diet and health (i.e. high-energy content of food, health benefits of unsaturated vs. saturated fats, and the effects of cooking foods in oil)
■ evaluate the use, benefits, drawbacks and risks of emulsifiers in foods.

Emulsions - An emulsion is a mixture of two (or more) liquids that are normally immiscible (do not mix together) such that one liquid is dispersed in another  Immiscible liquids Vegetable oils do not dissolve in water. If a mixture of oil and water is shaken, then left to stand, tiny droplets of oil will be seen to float upwards, and eventually
Vegetable oils: saturated and unsaturated oils (GCSE) - Structure A vegetable oil is a triglyceride extracted from a plant. A fatty acid is a long-chain carboxylic acid that may be saturated (only contains C-C single bonds) or unsaturated (contains C-C single and C=C double bonds). A fatty acid has the general formula of RCOOH, where R is s hydrocarbon that has a length of 16-20 carbon atoms. Three

Assessment and practical opportunities
■ pressing nuts (eg walnuts) between paper towels and studying the grease marks
■ steam distillation of lavender oil, orange oil, lemon oil, olive oil, rapeseed oil or vegetable oil
■ simple calorimetery investigations using small spirit burners or bottle tops to measure the energy released from various oils (weigh before and after, and measure the temperature change for a known mass of water)
■ making emulsions, eg oil/water, oil/vinegar
■ design and carry out an investigation into the effect of emulsifiers on the stability of emulsions
■ using bromine water to test fats and oils for unsaturation, eg testing sunflower oil against butter (using colorimeter to measure level of unsaturation).