EXTRACTION WITH COLD FAT (ENFLEURAGE)

I EXTRACTION WITH COLD FAT (ENFLEURAGE)

In the Grasse region of Southern France, flowers were processed by this method long before the modern method of extraction with volatile solvents was introduced. Generations ago Grasse, an ancient hill town located on the southern slopes of the Alpes-Maritimes and facing the Mediterranean, became the center of extensive flower plantations and, subsequently, of the French perfume industry. Grasse, like few places in the world, is favored by a mild climate, southern exposure and protection against north winds. There the cultivation of flowers for the extraction of their scent became a highly specialized agricultural occupation, passed down from generation to generation.

In the early days of perfumery, flower scents were extracted with fats, and the alcoholic washings of the perfumed fats represented the so-called floral extraits. These, blended with certain distilled essential oils,and tinctures, constituted the old-style perfumes. In the course of years this simple beginning led to our modern perfume industry with its wealth and variety of raw materials.

Despite the introduction of the modern process of extraction with volatile solvents, the old-fashioned method of enfleurage as passed on from father to son, and perfected in the course of generations, still plays an important role. Enfleurage on a large scale is today carried out only in the Grasse region, with the possible exception of isolated instances in India where the process has remained primitive.

The principles of enfleurage are simple. Certain flowers (e.g., tuberose and jasmine) continue the physiological activities of developing and giving off perfume even after picking. Every jasmine and tuberose flower resembles, so to speak, a tiny factory continually emitting minute quantities of perfume. This phenomenon was first studied by Passy²⁷ and later by Hesse.²⁸ Fat possesses a high power of absorption and if brought in contact with fragrant flowers readily absorbs the perfume emitted. This principle, methodically applied on a large scale, constitutes enfleurage. During the entire period of harvest, which lasts from eight to ten weeks, batches of freshly picked flowers are strewn over the surface of a specially prepared fat base (corps), left there (for 24 hr. in the case of jasmine and longer in the case of tuberose), and then replaced by fresh flowers. At the end of the harvest the fat, which is not renewed during the process, has become quite saturated with flower oil. The latter is finally extracted from the fat with alcohol and then isolated.

a. Preparation of the Fat Corps

b. Enfleurage and Défleurage.

c. Alcoholic Extraits

d. Absolutes of Enfleurage.

e. Absolutes of Chassis

------------------------

27 Compt. rend. 124 (1897), 783. Bull. soc. chim. [3], 17 (1897), 519.

28 Ber. 34 (1901), 293, 2928; 36 (1903), 1465; 37 (1904), 1462.

(a) Preparation of the Fat Corps. 

The success of enfleurage depends to a great extent upon the quality of the fat base employed. Utmost care must be exercised when preparing the corps. It must be practically odorless and of proper consistency. If the corps is too hard, the blossoms will not have sufficient contact with the fat, curtailing its power of absorption and resulting in a subnormal yield of flower oil. On the other hand, if too soft, the corps has a tendency to engulf the flowers so that the exhausted ones are difficult to remove and retain adhering fat, which entails considerable shrinkage and loss of corps. The consistency of the corps must, therefore, be such that it offers a semihard surface from which the exhausted flowers can easily be removed. Since the whole process qf enfleurage is carried out in cool cellars, every manufacturer must prepare his corps according to the temperature prevailing in his cellars during the months of the flower harvest.

Many years of experience have proved that a mixture of one part of highly purified tallow and two parts of lard are eminently suitable for enfleurage. This mixture assures a suitable consistency of the corps in conjunction with high power of absorption. The author carried out a series of experiments with various mixtures of vegetable fats, especially hardened vegetable fats which do not easily turn rancid. He also experimented with all kinds of antioxidants and glycoside splitting compounds, incorporating them into the corps before enfleurage. The result was a variety of interesting qualities and widely different yields of flower oils, but the highest quality of floral oils most true to nature resulted from the old-fashioned mixture of lard and tallow.

Mineral oils, too, have been suggested as bases for enfleurage work, and on a limited scale have been practically employed; but they offer no real advantage because their power of absorption is very small as compared with that of animal fats. Furthermore, it is exceedingly difficult to extract and isolate small quantities of absorbed flower oils from the mineral oils with alcohol or by other means.

Many other substances have been suggested as bases for enfleurage, and have been patented for this purpose, but none so far has attained any wide commercial application. For instance, according to French Patent 836,172, January 12, 1939 (I. G. Farbenindustrie A.-G.),²⁹ essential oils and natural flower oils are extracted by treatment of the plant material with esters of polyhydric aliphatic alcohols, containing at the most 6 carbon atoms, with fatty acids of high molecular weight, as obtained by oxidation of paraffin hydrocarbons of high molecular weight. Thus esters of glycol, glycerol, erythritol, mannitol, hexitol or trimethylolpropane may be used.

The fat corps is prepared in the Grasse factories during the winter months when they are not busy with the processing of flower crops. The crude pieces of tallow and lard, mostly of French and Italian origin, are purified according to a tedious old-fashioned method. The crude fats are carefully cleaned by hand, all adhering particles of skin and blood vessels removed, then crushed mechanically and finally beaten in a current of cold water. After all impurities have been removed, the fat is melted gently on a steam bath. Small quantities of benzoin (0.6 per cent) and alum (0.15 to 0.30 per cent) are then added. This preservation is very important, as otherwise the corps will turn rancid during the hot summer months. While benzoin acts as a preservative, the adding of alum causes impurities to coagulate during the heating ; when rising to the surface they can be skimmed off with a spoon. The warm fat is filtered through cloth, then left to cool and stand, so that any water may separate.

(During the past years chemistry has made great progress in regard to antioxidants for fats and oil, several of which could undoubtedly be used for preservation of the enfleurage corps employed in the Grasse region.)

The fat corps thus prepared is white, of smooth, absolutely uniform consistency, free of water and practically odorless. If well prepared and properly stored, it will resist rancidity for several years.

Some manufacturers also add small quantities of orange flower or rose water when preparing the corps. This seems to be done for the sake of convention. Such additions somewhat shade the odor of the finished product by imparting a slight orange blossom or rose note.

(b) Enfleurage and Défleurage.

Every enfleurage building is equipped with thousands of so-called chassis, which serve as vehicles for holding the fat corps during the process. A chassis consists of a rectangular wooden frame 2 in. high, about 20 in. long and about 16 in. wide. The frame holds a glass plate upon both sides of which the fat corps is applied with a spatula at the beginning of the enfleurage process. When piled one above the other the chassis form airtight compartments with a layer of fat on the upper and lower side of each glass plate.

Every morning during the harvest the freshly picked flowers arrive, and having first been cleaned of impurities, such as leaves and stalks, are then strewn by hand on top of the fat layer of each glass plate. Blossoms wet from dew or rain must never be employed, as any trace of moisture would turn the corps rancid. 

 PLATE 7. Enfleurage process. (Spreading of jasmine; flowers on top of the fat layer on

the glass plates of the chassis.)

The chassis are then piled up and left in the cellars for 24 hr. or longer, depending upon the type of flowers. The latter rest in direct contact with one fat layer (the lower one), which acts as a direct solvent, whereas the other fat layer (beneath the glass plate of the chassis above) absorbs only the volatile perfume given off by the flowers.

After 24 hr. the flowers have emitted most of their oil and start to wither, developing an objectionable odor. They must then be removed from the corps, which process, despite all efforts to introduce labor-saving devices, is still done by hand. The careful removal of the flowers (défleurage) is almost more important than charging the corps on the chassis with fresh flowers (enfleurage) and, therefore, the women doing this work must be experienced and skilled. Most of the exhausted flowers will fall from the fat layer on the chassis glass plate when the chassis is struck lightly against the working table, but since it is necessary to remove every single flower and every particle of the flowers, the women use tweezers for this delicate operation. Immediately following défleurage, that is, every 24 hr., the chassis are recharged with fresh flowers. For this purpose the chassis are turned over and the fat layer, which in the previous operation formed the top (ceiling) of the small chamber, is now directly charged with flowers. In the case of jasmine, the entire enfleurage process lasts about 70 days; daily the exhausted flowers are removed and the chassis recharged with fresh ones.

During the height of the harvest large quantities of flowers arrive every morning, which necessitates certain modifications in the process. Complications result from the fact that at the beginning and at the end of the harvest the quantities of flowers are very limited and, therefore, it is practically impossible to charge the chassis each day of the flower harvest with the same amount of flowers.

At the beginning of, and several times during, the harvest, the fat on the chassis is scratched over with metal combs and tiny furrows are drawn in order to change and increase the surface of absorption.

At the end of the harvest the fat is relatively saturated with flower oil and possesses their typical fragrance. The perfumed fat must then be removed from the glass plates between the chassis. For this purpose it is scraped off with a spatula and then carefully melted and bulked in closed containers. The final product is called pomade (pomade de jasmin, pomade de tubereuse, pomade de violet, etc.), the most highly saturated pomade being Pomade No. 36, because the corps on the chassis has been treated with fresh flowers 36 times during the whole process of enfleurage. At the beginning of the harvest every chassis is charged with about 360 g. of fat corps on each side of the glass plate, in other words, with 720 g. per chassis. Every kilo gram of fat corps should be in contact with about 2.5 kg. (preferably with 3.0 kg.) of jasmine flowers for the entire period of enfleurage, which lasts from 8 to 10 weeks. The quantities differ somewhat in the case of other flowers. 

 PLATE 8. Défleurage process. (Removal of jasmine flowers from the chassis.)

At the end of the enfleurage, the fat corps has lost about 10 per cent of its weight because of various manipulations. In other words, the total yield of the fragrant Pomade No. 36 is about 10 per cent less than the fat corps originally applied to the chassis. Most of this loss is caused by fat adhering to the exhausted flowers when they are removed (défleurage) every 24 hr.

(c) Alcoholic Extraits.

In the early days of perfumery, the fragment pomades were employed directly; later they were extracted with high proof alcohol, the alcohol dissolving the natural flower oil from the pomade. These alcoholic washings are called Extrait No. 36 when made from Pomade No. 36; they reproduce the natural flower perfume to a remarkable degree. 

 FIG. 3.23. Sketch of a Battcuse for the extraction of flower concretes with alcohol.

(The agitation is in counter-rotary motion.)

Since no heat is applied during the process of enfleurage and during the washing of the pomades with alcohol, the extraits contain the natural flower oil as emitted by the living flowers. The only disadvantage exists possibly in a slight fatty "by-note" which can be eliminated to a certain extent by freezing and filtering the alcoholic washings. This slight fatty "by-note" is not always objectionable, as it imparts a certain roundness and fixation value to the finished perfumes, especially in conjunction with synthetic aromatics.

In order to prepare the extraits, the pomades are usually processed during the winter months when the factories are not busy with other work. For this purpose the pomades are charged into so-called batteuses (Fig. 3.23), closed copper vessels heavily tinned inside and equipped with strong stirrers around a vertical shaft. Several batteuses are arranged in batteries, the stirrers of each battery being driven by a powerful motor. The work, which goes on for several months, is carried out in cool cellars in order to prevent loss of alcohol by evaporation. Each batch of pomade is stirred for several days, the usual process of methodical extraction being applied. The alcohol employed in the process travels from one batch of pomade to the next (constituting in turn the third, second and first washings of successive batches), until it becomes enriched with flower oil and is drawn off as the alcoholic extrait. For the last washing, fresh alcohol is used, which also, in its turn, becomes gradually enriched by the continuous process just described. When extended to a fourth and fifth washing, this method extracts the pomades so efficiently that the exhausted fat is quite odorless. Being useless for new enfleurage it is usually employed for the making of soap.

The fully circulated washing called "Extrait No. 36" is run through a refrigerator and cooled to well below freezing temperature, if possible to 15^o, Most of the fat dissolved in the strong alcohol separates. The cold alcoholic solution (Extrait No. 36) is then filtered, also at low temperatures.

The quantity of alcohol to be employed for the washing of each batch of pomade is calculated with a view to obtaining, finally, 1 kg. of extrait per kilogram of pomade. Obviously some alcohol is lost by evaporation during the process of stirring.

The purified extraits reproduce the perfume of the living flowers remarkably well. In fact, during the nineteenth century these extraits were widely employed as bases of the classical French perfumes, and several conservative houses still continue this practice. Some of the well-known French perfumes undoubtedly owe their success partly to a high content of extraits. The washing of the pomades is carried out not only by the factories in Grasse but in some instances also by perfume manufacturers in Paris, London, Berlin and New York who possess the necessary batteuses and freezing apparatus.

Since World War I, however, most perfumers have discontinued the cumbersome practice of processing the pomades purchased in Grasse; besides, high custom barriers prevented the shipment of alcoholic washings from Grasse into foreign countries. For these reasons the Grasse manufacturers started to offer their extraits in a more concentrated and convenient form.

(d) Absolutes of Enfleurage.

As mentioned previously, an extrait contains not only the natural flower oil, but also a small quantity (about 1 per cent) of alcohol soluble fat, dissolved from the corps, which cannot be eliminated, even by cooling the extrait far below 0^o. When concentrating the extrait by distilling off the alcohol, the content of natural flower oil and fat increases correspondingly. Complete concentration in a vacuum still at low temperature results in a concentrated flower oil, free from alcohol, the so-called absolute of enfleurage.

The crude absolutes of enfleurage are usually of dark color and, because of their fat content, of a semisolid consistency. Lighter colored products of more liquid consistency can be obtained by certain methods of purification whereby more fat is eliminated. Further elimination of fat and purification increases the price of the final absolute. Every manufacturer has his own standards in this respect.

These so-called absolutes of enfleurage, absolutes of pomade, concentrates of pomade or liquid concretes were widely employed before the introduction of the more modern process of extraction with volatile solvents. Even today these absolutes of enfleurage find favor with some perfumers because of their lower price. Experts, however, claim that the absolutes of enfleurage when redissolved in alcohol are somewhat inferior to the original alcoholic extraits. Apparently during the process of concentration certain constituents of the natural flower oil, especially the most volatile and delicate ones, are lost.

A characteristic of absolutes of enfleurage is that they have a slight but noticeable "by-note" of vanillin quite alien to the true flower perfume. This note originates from the minute quantities of benzoin incorporated into the fat corps for protection against rancidity. Soluble in alcohol, the benzoin dissolves when the pomades are extracted with alcohol and upon concentration it accumulates in the absolute.

(e) Absolutes of Chassis.

When describing the process of enfleurage we mentioned that the flowers are removed from the fat corps on the chassis every 24 hr. These flowers arc not thrown away because they still contain that part of the natural perfume which was not absorbed by the fat. It must be borne in mind that the perfume or essential oil of the flowers consists not only of volatile constituents, but also of compounds of higher boiling range which are not so readily released by the flowers. The actual conditions are probably much more complicated and many physiological processes take place, which so far have not yet been fully elucidated.

The part of the natural flower oil which is retained by the flowers after removal from the chassis (défleurage) can be extracted from these partly exhausted flowers with a volatile solvent petroleum ether, for instance. Concentration of the solution results in a solid mass. (This product must not be confused with the concretes and absolutes obtained by extracting fresh flowers directly with volatile solvents.) The solid mass thus obtained contains a certain percentage of fat originating from the corps with which the flowers were in contact during the process of enfleurage; it is purified and made alcohol soluble by eliminating most of the fats at low temperature.

The final so-called absolute of chassis, a viscous, alcohol-soluble oil, possesses an odor differing somewhat from that of the absolute of enfleurage.

Absolute of enfleurage and absolute of chassis logically supplement one another because each represents only part of the total natural flower oil present in the living flowers. Yet, they are usually marketed separately, perhaps because the absolute of chassis is lower priced than the absolute of enfleurage.

Absolutes of chassis give excellent results in perfume blends, especially in conjunction with synthetic aromatics, the harsh notes of which are thereby softened and blended.