Emulsions and Hydrogenation Flashcards
What is an emulsifier?
Emulsifiers are food additives that prevent oil and water mixtures in food from separating.
How are some oils extracted?
Vegetable oils are natural oils found in seeds, nuts and some fruit. These oils can be extracted. The plant material is crushed and pressed to squeeze the oil out. Olive oil is obtained this way.
Besides crushing and pressing, how else can some oils be extracted?
Sometimes the oil is difficult to extract and has to be dissolved in a solvent. Once the oil is dissolved, the solvent is removed by distillation, and impurities such as water are also removed, to leave pure vegetable oil. Sunflower oil is obtained in this way.
What is the structure of vegetable oils?
Molecules of vegetable oils consist of glycerol and fatty acids.
Do vegetable oils have a high or low boiling point?
High boiling point
Fatty acids in some vegetable oils have single bonds, what does this mean?
The fatty acids in some vegetable oils are saturated: they only have single bonds between their carbon atoms.
Fatty acids in some vegetable oils have double bonds, what does this mean?
The fatty acids in some vegetable oils are unsaturated: they have double bonds between some of their carbon atoms.
What is the difference between monounsaturated fats and polyunsaturated fats?
Monounsaturated fats have one double bond in each fatty acid.
Polyunsaturated fats have many double bonds.
Which is the healthier option to have in your diet: saturated or unsaturated fats?
Unsaturated.
What do vegetable oils not do in water?
Dissolve.
What happens during an emulsion?
If oil and water are shaken together, tiny droplets of one liquid spread through the other liquid, forming a mixture called an emulsion.
How are emulsions different to the oil or water they contain?
Emulsions are thicker (more viscous) than the oil or water they contain.
What happens if an emulsion is left to stand?
If an emulsion is left to stand, eventually a layer of oil will form on the surface of the water. Emulsifiers are substances that stabilise emulsions, stopping them separating out.
Emulsifiers have two different ends, name them.
a hydrophilic end - ‘water-loving’ - that forms chemical bonds with water but not with oils
a hydrophobic end - ‘water-hating’ - that forms chemical bonds with oils but not with water.
The hydrophilic ‘head’ dissolves in the water and the hydrophobic ‘tail’ dissolves in the oil. In this way, the water and oil droplets become unable to separate out.
How is bromine water used to tell an unsaturated vegetable oil from a saturated vegetable oil?
Unsaturated vegetable oils contain double carbon-carbon bonds. These can be detected using bromine water (just as alkenes can be detected). Bromine water becomes colourless when shaken with an unsaturated vegetable oil, but it stays orange-brown when shaken with a saturated vegetable fat.
