Vanilla. Vanillinum, Vanillin.
Vanilla consists of the cured full-grown, but unripe fruits of Vanilla planifolia, Andrews (N.O. Orchideae), a climbing plant indigenous to Mexico, but cultivated in Java, Réunion, the Seychelles, etc. It is official in the U.S.P. The fruit of the vanilla plant, a slender capsule, 15 to 20 centimetres long, is collected in the late autumn when full grown, but just before it ripens, and is then submitted to a process of curing, the details of which vary in the different countries of production, during which the characteristic aroma is developed. The curing of the fruits consists essentially of a slow process of drying in warm air, either artificial or solar heat being utilised for this purpose. The cured fruits, which are dark brown or nearly black in colour, are tied into bundles and packed in tins, in which they gradually become coated ("frosted") with crystals of vanillin. Commercial vanilla pods are nearly black in colour, 15 to 20 centimetres long, and 6 to 9 millimetres thick. They are of a flattened cylindrical shape, tapering towards each end, wrinkled and flexible, the best varieties being covered with minute, glistening crystals of vanillin. The interior of the pod contains innumerable minute black seeds, embedded in a dark, aromatic, balsamic fluid secreted by papillae lining the cavity of the fruit. The best vanilla is Mexican, which occurs in long, narrow, well-frosted pods. Java vanilla is shorter, but is also very aromatic. Bourbon vanilla tapers rather abruptly, and has an odour resembling coumarin. Fruits gathered too early yield pale-coloured vanilla, lacking aroma. Vanillons are the cured fruits of uncultivated vanilla plants, and are usually of poorer quality. Vanilla contains about 20 per cent. of moisture, and, on incineration, yields about 4 or 5 per cent. of ash.
Constituents.—The chief constituent of vanilla is the aromatic, crystalline substance vanillin, which is the aldehyde of methylprotocatechuic acid; good beans contain from 2 to 2.75 per cent. Other constituents are vanillic acid, resin (4 per cent.), fat (11 per cent.), sugar (10 per cent.), etc. The unripe pods are said to contain coniferin, and two enzymes, one of which converts coniferin into coniferyl alcohol, and the other oxidises the coniferyl alcohol to vanillin.
Uses.—Vanilla is used as a flavouring agent, usually in the form of Tinctura Vanillae. It is also employed in perfumery.
- Tinctura Vanillae, U.S.P. and B.P.C.—TINCTURE OF VANILLA. Syn.—Essence of Vanilla.
- Vanilla, cut into small pieces, and bruised, to; refined sugar, in coarse powder, 20; alcohol, a sufficient quantity; distilled water, sufficient to produce 100. Used as a flavouring agent.
C8H8O3 = 152.064.
Vanillin, or methyl-protocatechuic aldehyde, C6H3OHOCH3COH, is the odorous principle of vanilla pods, Vanilla planifolia, Andrews (N.O. Orchideae), which contain about 2 per cent.; it is also found naturally in Siam benzoin, balsams of Peru and tolu, and in traces in many vegetable tissues. It is produced synthetically from eugenol, and from coniferin. It is official in the U.S.P. Vanillin occurs in the form of white crystalline needles, or colourless prisms, having the intense odour and taste of vanilla, and an acid reaction. The natural substance has the finer flavour. It is completely extracted from its solution in ether by shaking with saturated, aqueous solution of sodium bisulphite, from which vanillin may be reprecipitated by sulphuric acid. Melting-point, 80° to 81°. Boiling-point, 285°. It distils in a current of carbon dioxide without decomposition. On complete ignition, it leaves no residue. The aqueous solution gives with lead acetate a white precipitate of a lead compound soluble in hot water, from which it separates in scales on cooling. The aqueous solution is coloured blue by ferric chloride, becoming brown on boiling; from the liquid, on cooling, a white precipitate of dihydrodivanillin separates. If vanillin be warmed with concentrated alcoholic solution of sodium hydroxide, and chloroform be added, no odour of phenyl isocyanide should be developed on further warming (absence of acetanilide). By the action of nascent hydrogen vanillin is converted into vanillin-alcohol, C8H10O3; on oxidation it yields odourless vanillic acid, C8H8O4, which does not form the crystallisable aldehyde compound with sodium bisulphite. The acid is also produced when vanillin (vanillic aldehyde) is exposed to moist air. On fusing vanillin with potassium hydroxide, protocatechuic acid, C6H3(OH)2COOH, results. If vanillin, with twice its weight of pyrogallol, be dissolved in alcohol, and hydrochloric acid added to the solution, a blue-violet colouration will appear on evaporating the liquid in a porcelain dish; similarly, if phloroglucin replace the pyrogallol, a fiery-red colouration will be produced on evaporation. The latter is the well-known Günzberg's test for free hydrochloric acid in the stomach contents; the reaction is sensitive to 0.05 per cent. of free hydrochloric acid. Vanillin is subject to much adulteration—to the extent of 60 per cent. or more—the usual adulterants being benzoic acid, boric acid, acetanilide, coumarin, and, more recently, terpin hydrate. Being liable to deterioration from oxidation, it should be kept in well-closed bottles in a cool place and protected from light.
Soluble with difficulty in water; easily in boiling water; very easily in alcohol, ether, chloroform, carbon bisulphide, fatty and volatile oils, also in aqueous solutions of alkali hydroxides, forming compounds from which the vanillin may be reprecipitated by the addition of acids.
Uses.—It is extensively used in the manufacture of vanilla essences for confectionery, and in perfumery, but is rarely used in medicine except as a flavouring agent.
- Essentia Vanillini Composita, C.F.—Similar to Tinctura Vanillini Composita, N. F.
- Tinctura Vanillini Composita, N.F.—COMPOUND TINCTURE OF VANILLIN. Syn.—Compound Essence of Vanillin.
- Vanillin, 0.65; coumarin, 0.04; alcohol (95 per cent.), 20; glycerin, 12.5: syrup (U.S.P.), 12.5; compound tincture of cudbear, 1.6; water, sufficient to produce 100.