Transfer oils, or carrier oils, are natural oils, obtained by cold pressing, of the seeds of oil plants, or of fruit kernels. The most famous are olive, sunflower, linseed, rapeseed, peach, apricot, grape, avocado, almond, walnut oils.
They are rich in unsaturated fatty acids. They have the property of enclosing the small molecules of essential oils, which is why they are called transfer or carrier oils.
Their use in the preparation of flavored butters, to preserve the essential flavors inside the solid fats and prevent the volatilization of perfumes, brought them this name.