Expression is a method used to extract aromatic materials, specifically essential oils, from plant sources, primarily citrus peels. Unlike steam distillation, which uses heat and steam, expression involves mechanical pressure to squeeze out the volatile oils contained in the rind or peel of fruits.
Process: Citrus fruits such as oranges, lemons, and bergamots are commonly processed using expression. The fruit peel is mechanically pressed to rupture the oil-containing glands, releasing the essential oil along with some of the fruit's aromatic compounds. The resulting oil is then collected and used in natural perfumery, cosmetics, and aromatherapy.
Expression is favoured for citrus oils because it preserves the fresh, vibrant aroma of the fruit without exposure to heat, which can alter or degrade the delicate citrus scent. This method ensures that the extracted oils retain their true fragrance and therapeutic properties, making them valuable ingredients in fragrance compositions and other applications.