End Of Unit Questions Flashcards
What type of fuel is produced from vegetable oils?
Biofuel
What is used to test for an unsaturated oil?
Positive test: bromine water turns from orange to colourless in the presence of unsaturated fats
Why are some foods cooked in vegetable oil?
- cooks faster
- energy is absorbed into food
- tastes better
Describe how to make an emulsion from cooking oil and water
Shake, stir or beat vigorously or use an emulsifier
Mayonnaise is made from oil, vinegar and egg yolk. What is the purpose of the egg yolk?
Emulsifier, to prevent oil and vinegar separating
Why are emulsions more useful than separate oil and water?
- they are thicker
- have better texture
- better appearance
- ability to stick on or coat solids
Why should you know what type of fats are in food you eat?
Saturated fats can cause health issues
Sunflower seeds contain vegetable oil. Outline a method you could use to separate some oil from the seeds.
- crush seeds and collect the liquid
* add seeds to water, distill the mixture and collect the liquid
Describe the reaction and conditions used to hydrogenate vegetable oils. Why is this done?
React with hydrogen at 60*c with a nickel catalyst. This is done to harden the oils and make them saturated
Describe how an emulsifier works
They have a hydrophilic head that is attracted to water. They also have a hydrophobic tail that is attracted to oil. The tail goes into the oil and the head stays in the water, keeping the droplets dispersed in the water
Why are vegetable oils used as food and fuels?
They provide a lot of energy
