ABSTRACT
Extraction of flavor and aroma substances from naturally occurring raw materials is important because the compositions of flavors are often too complex to be synthesized economically. Raw materials are isolated from balsam, bark, berry, blossom, bud, fruit, grass, gum, heartwood, leaves, peel, root, seed, twig, wood, and resinous exudation. Extracts of flavor and aroma substances prepared from raw materials are termed pomade, concrete, absolute, resinoid, or tincture according to their production technique (1). In processing essential oils and natural extracts, steam distillation, solvent extraction, supercritical fluid extraction, and expression are the major methods. Steam distillation provides the essential oil, whereas solvent extraction provides both the essential oil and the oleoresins. Oleoresins are concentrated natural liquid flavorings that contain both volatile and nonvolatile flavor components. Essential oils are obtained from plant materials by steam distillation or water distillation. After condensation of the vapor phase, the oil separates from the aqueous phase and is removed. Essential oils consist of volatile, lipophilic substances that are mainly hydrocarbons or monofunctional compounds derived from the metabolism of mono-and sesquiterpenes, phenylpropanoids, amino acids, and fatty acids. Pomades consist of fats that contain fragrance substances and are produced by the enfleurage technique. Concretes are prepared by evaporation of residue substances that are extracted from fresh plant material with nonpolar solvents such as benzene, toluene, hexane, and petroleum ether, as shown in Fig. 1. Concretes contain viscous waxy compounds with volatile fragrance materials. Concretes and pomades are not completely soluble in ethanol. Absolutes are prepared by taking up concretes in ethanol. Compounds that precipitate on cooling are then removed by filtration. After evaporation of the ethanol, a waxfree residue, the absolute, remains. Absolutes are completely soluble in ethanol. Resinoids are prepared by extracting plant exudates (balsams, oleo gum resins, natural oleoresins, and resinous products) with solvents such as methanol, ethanol, or toluene. The products are usually highly viscous to improve their flow and processing properties. Resinoids mainly consist of nonvolatile, resinous compounds and are primarily used for their excellent fixative properties. Tinctures are alcoholic solutions that are prepared by treating natural raw
materials with ethanol or ethanol-water solution. They can also be obtained by dissolving other extracts in these solvents.
