Oils are liquid fats. Fats are esters of carboxylic acids which are either saturated (do not contain double bond) or unsaturated (contain one or two double bond). These esters are derived from a single alcohol called glycerol and are called glycerides. Usually fats with greater percentage of un-saturation tend to be in liquid state and fats with greater percentage of saturation tend to be in solid state at room temperature.
Vegetable fats are all liquid fats since they belong to esters of long chain fatty acids with one or more double bonds while most of the animal fats are solid in nature since they are all esters of long chain fatty acids which do not contain double bond.
Coconut oil unlike other vegetable oils contains nearly 91 per cent of saturated fatty acids. Even though it has greater percentage of saturation it remains as liquid fat instead of solid fat.
Its liquid nature is due to the presence of more number of short chains (C12 and C14) saturated fatty acids (only fats with long chain saturated fatty acids remains as solid fats). Because of the greater percentage of saturation coconut oil can easily be solidified at low temperature and becomes solid during winter when the temperature falls below 20 degree centigrade.
Oils which contain unsaturated fatty acids can also be solidified if their double bonds are broken by hydrogenation at very high temperature. Vegetable ghee and vanaspathi are made in this way. This process is called hardening. In the case of coconut oil this hardening occurs not because of hydrogenation but because of low temperature.
