I was rather surprised to find lipids on the GCSE chemistry syllabus, but they nevertheless are!
Fats and fixed oils are generally triglycerides of fatty acids. There are also mono- and diglycerides of fatty acids such as the food additive E471. Each molecule is based on glycerol, commonly known as glycerine, an alcohol with three hydroxyl (-OH) groups. Alcohols are simply organic compounds with hydroxyl groups and include the familiar ethanol or ethyl alcohol, but also a large number of other compounds not generally thought of as alcohol such as phenol and retinol (vitamin A) These groups are dropped in favour of three fatty acids, which can be the same or different from each other. A fatty acid is a long-chain organic acid which, apart from the carboxyl group (-COOH) which makes it acidic, may contain zero, one or several double bonds between its carbon atoms. Saturated fats contain no double bonds, monounsaturates one and polyunsaturates several. Examples of saturated fatty acids include palmitic and stearic, found in palm oil and lard, monounsaturated fatty acids include oleic acid, which is found in olive oil, and polyunsaturates include arachidonic acid, which is a component of peanut oil. Lauric acid is a small fatty acid with a twelve-carbon chain.
Fats and oils mainly differ in melting point, with fats having a melting point above 20 Celsius (Centigrade) and oils below it. A few oils, such as walnut and grape seed oil, have a melting point fairly close to room temperature and are therefore waxy or solidify in cold conditions such as in warehouses. Saturated fats are also harder than unsaturated ones, and tend to be animal products rather than vegetable, though there are exceptions such as coconut oil.
Saturated fats are widely considered to be worse for the health than unsaturated ones, although this applies to cis fats rather than trans, of which more later. They are often considered to be a factor in the furring up of the arteries which contributes to heart disease and circulatory problems, also including strokes. There are certain things i'm not saying in this video because of the nature of the subject.
As unsaturated fats are less viscous than saturated, they are sometimes altered to make them thicker so they can be used in margarine. This is done by bubbling hydrogen through vegetable oil in the presence of nickel as a catalyst, which buckles the fatty acid residues into L shapes, making them tend to hook onto each other and therefore thickening them. This is probably very unhealthy. A rare biological example of trans fat is found in sebum, the bactericidal secretion which keeps skin oily. Heating a cis fatty acid can also convert it to a saturated form, but again this is unhealthy.
Oils are also important in emulsions. These are suspensions of droplets of one liquid in another, achieved by means of saponins, detergents and other emulsifiers. Examples of these include margarine, skin cream and mayonnaise.
Finally, vegetable oil can be made into biodiesel. There are plenty of videos on here which address that process and i don't know the details, so i'll leave that to them, but in general terms, potassium hydroxide is added to remove the glycerol, which is itself then removed and the potassium is then replaced with hydrogen. However, this is controversial as it drives up the cost of oil crops which could be used as food and also means that more land is devoted to fuel crops rather than food.
I keep feeling i'm missing the spot with what i'm doing. This is OK as an educational video although i feel i shouldn't gloss over the biodiesel and TFA controversy quite as much as i should. However, i also seem to be making the wrong videos somehow. I'm also rather surprised this is even on the GCSE chemistry syllabus, although i am aware that hydrogenation of vegetable oil was part of the GCSE i studied in 1993.
One thing i am happy with, though, is the outro screen:
Oh, who am i kidding? Nobody's reading this anyway. Bye.
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