Cardamom is a polymorphic species of the monotypic genus Elettaria. True cardamom or lesser cardamom is a monocot belonging to the family Zingiberaceae under the natural order Scitaminae. The varietal status of true cardamom has been designated as Elettaria cardamomum var. cardamomum (syn. var. minor Watt; var. minuscula Burkhill, Purseglove 1975). The seeds, contained in the dried fruits (capsules) and possessing a characteristic pleasant aroma, are the cardamom of commerce. Rosengarter () ranked cardamom as the third costliest spice in the world. In India it is the second most important spice next to black pepper ().
The plant is a tall perennial shrub (), the aerial part of which consists of 10-20 erect, leafy shoots (pseudo-stem), 2-5.5 m tall and made of leaf sheaths. The shoots and the panicle emerge from a horizontal subterranean woody rhizome. Each panicle bears numerous small, white or pale-green flowers characterized by a conspicuous labellum with violet streaks radiating from the center. The flowers are hermaphrodites. The ripe fruit () is an ovoid trilocular capsule containing 15-20 aromatic seeds.
Cardamom cultivation is mainly concentrated in the southern states of India, i.e., Kerala, Karnataka, and Tamil Nadu. Guatemala, Tanzania, and Sri Lanka are the other major cardamom producing countries. New Guinea, Costa Rica, El Salvador, and Honduras have also emerged in recent years as producers and suppliers of cardamom in the world market. The average annual world production of cardamom is presently estimated around 10000 t, shared by India (40%), Guatemala (45%), and other countries (15%) ().
The dried fruits (capsules) of Elettaria cardamomum var. cardamomum are the true cardamoms. The spice obtained by drying the fruits of various Amomum and Aframomum species and also that of wild Elettaria varieties are often referred as “false cardamoms”. They are regarded as being much inferior in aroma and flavor (). Based on the size of the fruit, a botanical variety of true cardamom other than var. cardamomum has been recognized, namely, var. major Thwaites. The fruit of the var. major is larger and longer (2.5-5 cm), with numerous larger and less aromatic seeds than that of the var. cardamomum. It is known as Long Wild Cardamom and is less common in trade compared to var. cardamomum.
Medicinal Importance and Secondary Metabolites
Cardamom is valued for its dried capsules, containing highly aromatic seeds used directly as a flavoring material in three forms: whole decorticated seeds and ground. It is from the decorticated seeds that the essential oil (steam distillation) and oleoresin (solvent extraction) are extracted. In the whole or ground form, cardamom is used mainly for domestic culinary purposes. In Asia, it is a masticatory as well. It is used as a flavoring in a variety of spiced rice, meat, and vegetable preparations, puddings, sweets, and certain beverages. In the Middle East, cardamom has been traditionally used to flavor coffee. In European countries, the spice is used in curry powders, sausages, soups, canned fish, and also to flavor tobacco. A range of baked goods including cakes, buns, pastries, and bread are flavored with cardamom.
Cardamom oil finds its main application in the flavoring of processed foods, cordials, bitters, and liqueurs and occasionally in perfumery. The oleoresin also has similar applications but is less extensively used.
Cardamom has distinctive medicinal properties as well, and is official in most pharmacopoeias. In India, the tincture of cardamom seed is used in the indigenous systems of medicine to strengthen the digestive, respiratory, and urogenital systems (). Kirtikar and Basu () reported tonic, stimulant, stomachic, and emmenagogricue properties of the spice. According to them, it is administered internally in diseases of the liver and uterus, and externally to tumors of the uterus. Cardamom is reported to have curing properties in cases of rheumatism, bronchitis, poisoning, itching, and furuncles (). The aqueous extract of the rhizome of the cardamom plant is a good tonic and is claimed to have laxative properties. Cardamom oil has an antibacterial activity (). Nayak and Dutta () reported the bactericidal property of cardamom oil against Vibrio comma in vitro at dilutions 1:1000-1:15000, ineffective against cholera in vivo.
Cardamom seed contains volatile oil, fixed (fatty) oil, protein, cellulase, pentosans, sugars, starch, silica, calcium oxalate and minerals (). The major constituent of the seed is starch (45-50%) and that of the capsule (husk) is crude fiber (20-30%) (). The composition of the spice may vary to some extent between individual sample lots, owing to intrinsic differences between cultivars, environmental variations in the growing tract, maturity at harvesting, curing or drying and packing procedures, and duration of storage (). Several reports are available on the extent of variations in the composition of nonvolatile as well as volatile constituents of spice entering international trade.
Elettaria cardamomum seed on solvent extraction gives a greenish oleoresin containing about 70% volatile oil (). Nearly 40 constituents have been isolated from the cardamom oil obtained by steam distillation () and many of them are present only in traces. Nevertheless, they contribute towards the characteristic aroma of cardamom. The fruity sweet aroma of cardamom is contributed by the alcohol linalool and the esters linalyl acetate and alpha-terpinyl acetate (). The camphorous odor is imparted by the cineoles, particularly 1,8-cineole ().
Cardamom is valued as a spice for its dried capsules containing highly aromatic seeds. It is from the decorticated seeds from which the essential oil and oleoresin are extracted. Cardamom oil finds its main application in the flavoring of processed foods, cordials, bitters, and liqueurs and occasionally in perfumery. It has distinctive medicinal properties as well. It is reported to have curing properties in rheumatism, bronchitis, poisoning and itching, and has antibacterial and laxative properties. Selected plants have been clonally multiplied in vitro through shoot primordium culture and were field tested. Studies on the in vitro production of secondary metabolites, though lacking, would be highly rewarding for the selection of high-yielding clones through cell culture ().
Selections from the book: “Medicinal and Aromatic Plants IV”, 1993.