Carrier oils are fatty oils called triglycerides. Triglycerides are esters of glycerol. Carrier oils are differentiated by their unique Fatty Acid profile. Fatty acids can be saturated (do not contain double bonds), e.g. Palmitic, Lauric, Stearic, Myristic or unsaturated (contain one ore more double bonds), e.g. Alphas and Gamma linoleic acid.

Carrier oils are extracted either by cold expression or by a combination of cold expression and solvent extraction or by solvent extraction alone. The yield of some carrier oils is so low by cold expression, e.g. Grapeseed oil and so these are produced by solvent extraction.

Carrier oils easily become oxidised during the manufacturing process and causes the oil to become rancid. This rancidity gives the oil a malodour. To remove the malodour the oil is washed with an alkali (usually sodium hydroxide). This is called the refining process.

In cold conditions the higher molecular weight triglycerides precipitate out, making the oil cloudy. The refining process is therefore combined with a process called ‘Winterising’ to prevent this from happening. This involves cooling the oil to a set temperature and allows the heavy triglycerides to precipitate out. These are then removed by filtration.