OLEUM SESAMI.

Botanical Origin—Sesamum indicum DC., an erect, pubescent annual herb, 2 to 4 feet high,[1729] indigenous to India, but propagated by cultivation throughout the warmer regions of the globe, and not now found anywhere in the wild state. In Europe, Sesamum is only grown in some districts of Turkey and Greece, and on a small scale in Sicily and in the islands of Malta and Gozo. It does not succeed well even in the South of France.

History—Sesamé is a plant which we find on the authority of the most ancient documents of Egyptian, Hebrew,[1730] Sanskrit, Greek, and Roman literature, has been used by mankind for the sake of its oily seeds from the earliest times. The Egyptian name Semsemt already occurring in the Papyrus Ebers, is still existing in the Coptic Semsem, the Arabic Simsim, and the modern Sesamum. The Indian languages have their own terms for it, the Hindustani Til, from the Sanskrit Tila, being one of the best known.[1731] Tila already occurs in the Vedic literature. In the days of Pliny the oil was an export from Sind to Europe by way of the Red Sea, precisely as the seeds are at the present day.

During the middle ages the plant, then known as Suseman or Sempsen, was cultivated in Cyprus, Egypt and Sicily; the oil was an article of import from Alexandria to Venice. Joachim Camerarius gave a good figure of the plant in his “Hortus medicus et philosophicus” 1588 (tab. 44). In modern times sesame oil gave way to that of olives, yet at present it is an article which, if not so renowned, is at least of far greater consumption.

Production—The plant comes to perfection within 3 or 4 months; its capsule contains numerous flat seeds, which are about ²/₁₀10 of an inch long by ¹/₂₀ thick, and weigh on an average ¹/₁₆ of a grain. To collect them, the plant when mature is cut down, and stacked in heaps for a few days, after which it is exposed to the sun during the day, but collected again into heaps at night. By this process the capsules gradually ripen and burst, and the seeds fall out.[1732]

The plant is found in several varieties affording respectively white, yellowish, reddish, brown or black seeds. The dark seeds may be deprived of a part of their colouring matter by washing, which is sometimes done with a view to obtain a paler oil.[1733]

We obtained from yellowish seeds 56 per cent. of oil; on a large scale, the yield varies with the variety of seed employed and the process of pressing, from 45 to 50 per cent.

Description—The best kinds of sesamé oil have a mild agreeable taste, a light yellowish colour, and scarcely any odour; but in these respects the oil is liable to vary with the circumstances already mentioned. The white seeds produced in Sind are reputed to yield the finest oil.

We prepared some oil by means of ether, and found it to have a sp. gr. of 0·919 at 23° C.; it solidified at 5° C., becoming rather turbid at some degrees above this temperature. Yet sesame oil is more fluid at ordinary temperatures than ground-nut oil, and is less prone to change by the influence of the air. It is in fact, when of fine quality, one of the less alterable oils.

Chemical Composition—The oil is a mixture of olein, stearin and other compounds of glycerin with acids of the fatty series. We prepared with it in the usual way a lead plaster, and treated the latter with ether in order to remove the oleate of lead. The solution was then decomposed by sulphuretted hydrogen, evaporated and exposed to hyponitric vapours. By this process we obtained 72·6 per cent. of Elaïdic Acid. The specimen of sesamé oil prepared by ourselves consequently contained 76·0 per cent. of olein, inasmuch as it must be supposed to be present in the form of triolein. In commercial oils the amount of olein is certainly not constant.

As to the solid part of the oil, we succeeded in removing fatty acids, freely melting, after repeated crystallizations, at 67° C., which may consist of stearic acid mixed with one or more of the allied homologous acids, as palmitic and myristic. By precipitating with acetate of magnesium, as proposed by Heintz, we finally isolated acids melting at 52·5 to 53°, 62 to 63°, and 69·2° C., which correspond to myristic, palmitic and stearic acids.

The small proportion of solid matter which separates from the oil on congelation cannot be removed by pressure, for even at many degrees below the freezing point it remains as a soft magma. In this respect sesamé oil differs from that of olive.

Sesamé oil contains an extremely small quantity of a substance, perhaps resinoid, which has not yet been isolated. It may be obtained in solution by repeatedly shaking 5 volumes of the oil with one of glacial acetic acid. If a cold mixture of equal weights of sulphuric and nitric acids is added in like volume, the acetic solution acquires a greenish yellow hue. The same experiment being made with spirit of wine substituted for acetic acid, the mixture assumes a blue colour, quickly changing to greenish yellow. The oil itself being gently shaken with sulphuric and nitric acids, takes a fine green hue, as shown in 1852 by Behrens, who at the same time pointed out that no other oil exhibits this reaction. It takes place even with the bleached and perfectly colourless oil. Sesamé oil added to other oils, if to a larger extent than 10 per cent., may be recognised by this test. The reaction ought to be observed with small quantities, say 1 gramme of the oil and 1 gramme of the acid mixture, previously cooled.

Commerce—The commercial importance of Sesamé may be at once illustrated by the fact that France imported in 1870, 83 millions; in 1871, 57½ millions; and 1872, 50 millions of kilogrammes (984,693 cwt.) of the seed.[1734]

The quantity shipped from British India in the year 1871-72 was 565,854 cwt., of which France took no less than 495,414 cwt.[1735] The imports of the seed into the United Kingdom in 1870 were to the value of only about £13,000.

Sesamé is extensively produced in Corea and in the Chinese island of Formosa, which in 1869 exported the exceptionally large quantity of 46,000 peculs[1736] (1 pecul = 133 lb.). Zanzibar and Mozambique also furnish considerable quantities of sesamé, whilst on the West Coast of Africa the staple oil-seed is Ground-nut (Arachis hypogæa L. p. 186). The chief place for the manufacture of sesamé oil is Marseilles.

Uses—Good sesamé oil might be employed without disadvantage for all the purposes for which olive oil is used.[1737] As its congealing point is some degrees below that of olive oil, it is even more fitted for cool climates. Sesamé seeds are largely consumed as food both in India and Tropical Africa. The foliage of the plant abounds in mucilage, and in the United States is sometimes used in the form of poultice.