As was stated in the section on "Distillation," most essential oils are today isolated from the respective plants, or parts of plants in which they occur, by the process of distillation. A few essential oils i.e., those present in the peels of citrus fruit can be, and in large part are, obtained by cold pressing, which yields products of superior quality.
In our discussion of distillation it was emphasized that the process of distillation suffers from several inadequacies: the relatively long action of steam or boiling water on the plant material affects some of the more delicate constituents of the oil deleteriously ; hydrolysis, polymerization and resinification may and do take place; high boiling constituents, especially if somewhat soluble in water, are not carried over by steam, and are therefore lacking in the distilled oil. Other constituents dissolve partly in the distillation water, and cannot readily be recovered. As a result of all these factors, a distilled oil does not always represent the natural oil as it originally occurred in the plant.
A few types of flowers and this is the case with some very delicate ones yield no direct oil at all on distillation. The oil is either destroyed by the action of steam, or the minute quantities of oil actually distilling over are "lost" in the large volume of distillation water from which the oil cannot be recovered. This applies to jasmine, tuberose, violet, jonquil, narcissus, mimosa, acacia, gardenia, hyacinth and a few others. When hydrodistilled, these flowers yield either practically no oil, or in such low yield, or of such inferior quality, that for all purposes it is useless. Therefore, flowers of this type must be processed by methods other than distillation. This fact was recognized empirically hundreds of years ago when such flowers were treated by maceration in cold or hot fat, which process yielded fragrant pomades. From this primitive beginning there developed in the Grasse region of Southern France, in the course of many years, a highly specialized industry, employing the processes of maceration and of enfleurage and, for the last forty years, the modern process of cold extraction with volatile solvents. Despite similar, but much less important developments in other parts of the world (Bulgaria, Egypt, Algeria, Sicily, Calabria, Madagascar, etc.), Grasse has remained the center of this picturesque and charming industry, which today supplies the perfume manufacturers with a great variety of highly prized so-called "natural flower oils." Representing the authentic scents as exhaled by the flowers, these flower oils are the finest and most delicate ingredients at the disposal of the modern perfumer, enabling him to create masterpieces of his art by skillful application and blending.
The term "natural flower oil," as used today commercially, does not include the distilled essential oils; it applies only to flower oils obtained by the methods of enfleurage, maceration and extraction with volatile solvents, which will be described later in detail. A few oils--e.g., those derived from rose petals and from the blossoms of the sour (bitter) orange tree can be isolated either by distillation or by extraction. The oils are then called essential oils and natural flower oils, respectively, the latter reproducing and representing the original scent of the flowers in a more complete way. It is principally the elaborate apparatus required and the higher cost of manufacturing which prevent a more general adaptation of the process of extraction.





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