Vanilla is an herbaceous orchid climber found in the tropics of both hemispheres. A valuable spice, its fruits, commercially known as beans, become aromatic on curing due to the development of an aromatic principle called vanillin. Vanilla beans and derivatives are primarily used in food flavouring, especially, confectionery, ice creams, liquors and baked goods. Extracts and tinctures are prepared from beans. The average concentration of vanilla extract seen in various items are 200 ppm in non-alcoholic beverages, 3000 ppm in ice-cream, 4000 ppm in candy, 1900 ppm in baked goods, 2000-4800 ppm in icings, 1050 ppm in syrups and 2700 ppm in toppings. Vanilla is also used in perfumery and to a small extent in medicine. Lately, synthetic vanillin, which is cheaper and more convenient, is often used instead of vanilla. However, the aroma of genuine vanilla cannot be matched because it is the result of the natural balance of vanillin and small quantities of other aromatic components contained in the pods.
Vanilla is an orchid, belonging to the family Orchidaceae. The genus Vanilla comprises of over 100 species of stout, scandent, terrestrial or epiphytic herbs. But only three of these are an important source of vanillin. They are:
- Vanilla frangrance ,V. Planifolia - Produces short thick pods.
- Vanilla pompona. - Known as West Indian vanilla, it is cultivated in Trinidad and Central America. The largest pods are found in this variety.
- V. tahitensis – Also called Tahitian Vanilla, it is found in Hawaii. It is fleshy, herbaceous, perennial vine.
Vanilla planifolia is the most popular and commercially cultivated species. A climber that grows wild in forests, the plant clings and climbs through its aerial roots seen in nodes. Leaves are opposite, sessile, oblong and 10-23 cms long. Racemose inflorescences emerge from leaf axils about 8 cms long, usually unbranched bearing 20-25 flowers. It usually takes 50-60 days for the appearance of fully developed flowers from buds. Flowering is not synchronous in this species. Each flower stays open just for a single day. Blooming period continues for 14-30 days in an inflorescence. In a vine, 7-15 inflorescences are produced. Flowers are large, pale green, bisexual and zygomorphic. Sepals and petals look alike and are referred to as perianth. The lower petal is short, broad and modifies into a labellum that envelopes the central structure called the column (gynostemium). The column bears a single stamen with two pollen masses (pollinia) covered by a hood. Right below it is the stigma that is covered by a flap like rostellum, which prevents natural pollination. Ovary is slender and 4-5 cms long. Flowers bloom from the base upward. Pollen fertility is 72-87%. Flowers are pollinated through melapone bees and hummingbirds. Over 70% of the flowers develop into fruits. The fruits are capsules or pods. Pendulous, cylindrical, three angled and up to 21 cms long, these fruits mature in 10-12 months.
A humid, moist, tropical climate, with a temperature range of 25-32 ºC is best suited for Vanilla. It grows well at an elevation of 700–1500 m with an annual rainfall of 2500 mm.well distributed for a period of 9 months and a dry period for 3 months.
It is adaptable to a wide range of soil types provided there is plenty of organic matter and proper drainage. The preferred pH range is 6-6.5.
Vanilla is usually propagated by stem cuttings. 60-120 cms long vines are selected as planting material. The vines are coiled and buried inside the soil. Plants raised from lengthy cuttings start flowering early whereas those raised from short cuttings take 3-4 years. Therefore, cuttings with less than 5-6 internodes and 60 cms length may not be used for planting. Due to limited availability of planting materials, tissue cultured planting materials have started gaining popularity. Unlike other plants, growing Vanilla requires extra attention and care. It flourishes in partial shade. Vines may be trained on trellises or trees with low branches and rough, small leaves. Trees like Jatropha, Plumeria alba, Casuarina equisetifolia, Erythrina, Glyricidia, Bauhinia or Silver oak are often used for Vanilla plants. The supports are planted 2.5 to 3.0 m between rows and 2m within the row, thus allowing for 1600 to 2000 plants per hectare. If limb cuttings are used, it should have a diameter of 4-6 cms and about 1.5 to 2 m length. The supporting saplings may be established 6 months before planting the vanilla cutting. Vanilla is generally planted when the weather is slightly humid, wet. While planting the cuttings, 3-4 basal leaves on the cutting should be removed and this defoliated portion must be laid on loose soil and covered with a thin layer of about 2-3 cm soil. The growing end is gently tied to the support. Artificial shade with suitable material may be provided to the cuttings. It takes 4-8 weeks for the cutting to strike roots and to show initial signs of growth.
Once established, the vines have to be given constant attention. The roots, which are mainly confined to the mulch and surface layer of the soil, must not be disturbed. When the supporting trees have grown, they are pruned early to introduce branching so as to give more shade and protection to the growing vines. If the trees are of the evergreen variety, they should be pruned before the rains to allow for more sunlight. The pruned vegetation is chopped and applied as mulch in the plantation. Decomposed mulch is the main source of nutrients to vanilla. Animal sources of manure are not generally applied. Annually, vines are usually fed with 40 to 60 g N, 20 to 30 g P2O5 and 60-100g K2O. This quantity may be given in two or three splits for efficient uptake. Part of the fertilizers can also be given through foliar spray. A vine that is growing on a tree will rarely blossom if it is left to grow upwards. Hence, vines are allowed to grow up to 1.50 m and then tied horizontally on a branch of the supporting tree and later coiled round it. This induces better flower production in this portion of the vine.
Anthracnose (Calospora vanillae) is a serious disease that attacks almost all parts of a Vanilla plant. Root rot, Fusarium betatis var. vanillae is a limiting factor in certain areas. It can be controlled by spraying suitable fungicides. The bug, Trioza litseae is one of the most common pests that attack the buds and flowers of vanilla. Usually controlled by any systemic insecticide.
The vines commence flowering in the second or third year depending on the length of cutting used. Due to the peculiar structure of the flower described earlier artificial pollination by hand is the rule for fruit setting. A simple procedure, it is done easily by children and women. Using a pointed bamboo splinter or pin the .anther is pressed against the stigma with the thumb and thus smearing the pollen over it. Generally, 85-100% success is obtained by hand pollination. The ideal time for pollination is 6 a.m. to 1 p.m. unfertilised flowers fall off within two or three days. Normally 5-6 flowers per inflorescence and a total of 10-12 inflorescence per vine are pollinated. The excess flower buds are nipped to permit development of good pods. Pods usually take six weeks to attain full size from fertilization and 4-10 months to reach full maturity, depending upon the location. When unripe, the bean is dark green in colour, but when ripe it starts yellowing from its distal end. This is the optimum time for harvesting the bean. If left on the vine, the bean turns yellow and splits giving out a small quantity of reddish brown oil called the balsam of vanilla. Eventually it becomes dry, brittle and finally scentless.
The yield varies depending upon the age of the vines and the method of cultivation. Normally, it starts yielding from the third year and the yield goes on increasing till the seventh or eighth year. Thereafter, it slowly declines till the vines are replanted after 14-15 years. Typically, a middle-aged plantation may yield 300-400 kgs cured beans per hectare.
Post Harvest Technology
Artificial methods are usually employed to cure vanilla. The aroma principle, vanillin is developed as a result of enzyme (Beta Glucosidase) action on the glucosides contained in beans.during the process of curing. Any curing method involves the following four stages
- Killing the vegetative life of the beans to allow for enzymatic reaction
- Raising the temperature to promote reaction and achieve rapid drying to prevent harmful fermentation
- Slow drying for the development of different fragrant substances
- Conditioning the product by storing it for a few months
The following are some of the curing methods of which Bourbon method is most commonly used for V. planifolia
- Peruvian process
- Guiana process
- Mexican process
- Bourbon process
Bourbon Method - Also called scalding, beans are killed by hot water immersion. Beans are placed in perforated cylindrical baskets, which are then immersed in vats containing hot water, maintained at around 65ºC.Higher quality beans are scalded for about 2to 3minutes,while splits and beans deemed inferior, are scalded for 2-minutes or less. The metal vats, which are heated by a wood ﬁre, have a capacity for scalding about 1.5 tons of vanilla beans in 4 to 5 hours. The scalded beans are quickly dried and while still very hot are wrapped in dark cloth or a blanket. The wrapped beans are then placed in sweating chests lined with cloth and other insulating materials. After about 24 hours of sweating, the beans are removed from the chests and dried in the hot sun for about 2 to 3 hours, rolled up in insulating cloths to retain as much heat as possible, and taken indoors to be replaced in the sweating boxes. The process is repeated for 6 to 8 days. The beans lose moisture quite rapidly and become very malleable. In the subsequent drying phase, lasting 2 to 3 months, the beans are allowed to dry slowly in properly ventilated rooms. During this time the beans are regularly sorted to remove pods that are adequately dried and ready for the next step of conditioning. For conditioning, the beans are placed for about 3 months in the air-tight chests or waxed paper lined metal containers. During this period beans are regularly inspected to ensure the development of the desired ﬁnished product. Satisfactorily cured beans are again graded according to size and quality and then bundled for shipment
The most desirable beans will be 18 to 25 cms long, dark brown, highly aromatic, fleshy, free from mold, insects and blemishes. They are supple and small crystals of fragrant vanillin are visible on the surface. Theyre are available in three grades, viz.
Grade-1, which includes whole beans of minimum 11 cms length & Grade 2 and 3 that have a minimum of 8 cms length.
One kilogram of processed produce is obtained from 240-260 beans. The moisture content of the beans after processing is 24%. The vanillin content is 2.41% during the curing process.