Vanilla is the fully grown fruit of the orchid Vanilla fragrans. Vanilla is indigenous to South-Eastern Mexico, Gautemala and other parts of Central America, growing wild as a climber in the forests. Vanilla cultivation on a systematic basis began with the introduction of it into Java,
Seychelles, Tahiti, Comoro Islands, Martinique, Madagascar, Uganda etc. in the 19th century and early part of the 20th century. At present Malagasy Republic is the major producer of vanilla. It was introduced in India in 1835. It is now cultivated in very limited areas in Kerala, Karnataka and Tamilnadu.
Vanilla is a fleshy, herbaceous perennial vine, climbing by means of adventitious roots on trees or other supports. The roots are long, whitish, aerial, about 2mm in diameter and are produced singly opposite the leaves. The roots at the base ramify in the humus or mulch layer. The long, cylindrical, monopodial stem (1-2 cm dia) is simple or branched, succulent and brittle. It is dark green and photosynthetic with stomata. The internodes are 5-15 cm in length. Large, flat, fleshy, subsessile leaves are alternate, oblong-elliptic to lanceolate and are 8-25 cm long and 2-8 cm broad. The veins are numerous, parallel and indistinct. The petiole is short and thick. They are borne toward the top of the vine and are 5-8 cm long with upto 20-30 flowers, opening from the base upwards.
The flowers are large, waxy, fragrant, pale greenish-yellow and are about 10 cm in diameter. Pedicel short, tricarpillary ovary inferior, cylindrical, sepals three, oblong-lanceolate, obtuse to subacute, slightly reflexed at the apex. Two upper petals resemble the sepals in shape. The lower petal is modified as a trumpet-shaped labellum or lip. The tip of the lip is obscurely three-lobed and is irregularly toothed on its revolute margin. Dark coloured papillae form a crest in the median line. The gynostemium is long, hairy on the inner surface, bearing at its tip the single stamen. The concave sticky stigma is separated from the stamen by a thin, flap-like rostellum because of which self pollination is impossible. The fruit is a pendulous, narrowly cylindrical and obscurely three-angled capsule, known as bean. It contains ripe myriads of very minute globose seeds of about 0.3 mm in diameter.
Vanilla is strictly tropical in its requirements. It thrives well in hot and humid climate, from sea level to an elevation of about 900 m. A temperature range of 10-30oC and an annual rainfall of 150-250 cm are its optimum requirements. It grows well in well-drained sandy loams and alluvial and laterite soils having plenty of organic matter. It requires light shade and support for climbing and putting forth satisfactory growth. It is generally propagated through shoot cuttings, planted at a spacing of 2.5 m either way, in pits measuring 45 x 30 x 30 cm.
Vanilla is harvested when the pods are mature and split longitudinally. Fresh beans get the characteristic aroma due to enzymatic action during curing. The enzyme b-glucosidase act on the precursor glucovanillin which result in the harvested beans are subjected to a process of nightly sweating and daily exposure to the sun for about 10 days until they become deep chocolate-brown in colour. Then they are spread on trays in an airy shelter until dry enough for grading. The best grade may be covered with tiny crystals of vanillin. This coating is known as givre.
Aroma and flavour
The fragrance and flavour of vanilla is due to numerous compounds produced during the curing process, among which vanillin is the most abundant. Other compounds are vanillic acid and an oleoresin.
Culinary, medicinal and other use
Vanilla is world's most popular flavourant for numerous sweetened foods, several commercial food products, liquors, perfumes etc. Vanilla extracts or essence are extracted with alcohol and contains the aroma and flavour principles and sweetening/thickening agents. They are widely used as a flavouring par excellence for ice creams, soft drinks, chocolates, confectionary, candy, tobacco, baked foods, puddings, cakes, cookies, liquors, and in perfumery. Vanilla sugar is a mixture of vanilla extracts and sugar. Vanilla tincture is used for pharmaceutical uses. Of late technical grade vanillin is used as a chemical intermediate in the production of a number of pharmaceutical products.