Ginger is a slender perennial herb with robust branched rhizome borne horizontally near surface soil. Ginger rhizomes are used in 3 different ways - fresh, preserved and dried. Fresh or green ginger is consumed as a vegetable. Immature ginger, preserved in sugar syrup, is mainly used as a desert. Dried rhizomes constitute the spice and is known for its flavour, pungency and aroma. A critical ingredient in curry powder, it is also used in the production of ginger beer, ginger oil and ginger wine. Preserved ginger is prepared by boiling tender fleshy peeled rhizomes and soaking it in sugar syrup. Crystallized ginger is produced in the same way, but it is dried and dusted with sugar. While the rhizome yields essential oil, it lacks the pungent principle. However, an oleoresin is also extracted from it, in which the full pungency of the spice is preserved. It is used in the manufacture of flavouring essences, in perfumery and medicines. Widely known for its medicinal properties, when consumed it known to work as a carminative and externally it is used as a rubefacient and counter irritant.
Ginger belongs to the family Zingiberaceae and the species Zingiber officinale L. It is a slender perennial herb that grows up to 1 m tall, with robust branched rhizomes bearing leafy shoots. The rhizome is thick, laterally compressed, palmately branched with small distichous scales and fine fibrous roots. Leafy shoots formed of long leaf sheaths, bearing 8-12 distichous leaves, lamina sessile, linear, lanceolate; ligule 5 mm long, glabrous and bilobed. Inflorescence arises direct from rootstock, spiciform, 15-25 cms long, spike cylindrical and cone like. Bracts appressed are ovate or elliptic, one flower is produced in the axil of each bract; calyx is thin, tubular, 3-toothed and the corolla tube is 2-2.5 cms long with 3 yellowish lobes; filament of stamen is short and broad, the anther connective prolonged into a slender curved beak-like appendage; stigma is usually protruding, just below the apex of the appendage; ovary is 3-locular with many ovules per locule; fruits are seldom produced and are thin walled, 3-valved capsule with small black arillate seeds.
The plant requires a warm and humid climate. It thrives well in areas located at mean sea level to 1500 m. A well distributed rainfall of 1500-3000 mm, during the growing season and dry spells during land preparation and harvesting are congenial. It requires rich soil with high humus content. Ginger is not cultivated continuously in the same field, due to its exhaustive nature, shifting cultivation or crop rotation is advised. The crop cannot survive waterlogging and requires soils with good drainage. Ginger is propagated vegetatively. The seed rhizome is usually 2.5-5 cms long with at least one good bud. They are usually preserved in covered pits. Smoking of seed rhizomes is also practiced to enhance germination and ward off pests and diseases. There are several clones that are available that differ in the fiber content of the rhizomes and yields. Rhizomes with less fiber, which varies from 1.7-9.0% have a higher demand. Land is usually prepared for cultivation during April and May. A good tilth is required in order to produce healthy well shaped rhizomes. Usually in hard soils, the rizhomes are often malformed. Rhizome seeds at the rate of 1000-1500 kg/ha are planted 5-10 cms deep on raised beds with 20-30 cms spacing. Ginger benefits greatly from the application of organic manures. 25-30 tons/ha of cattle manure or compost is applied at the sowing stage. Fertilisers are applied at 75:50:50 kg N, P2O5 and K2O/ha. Full dose of P and half of K may be applied as basal dose. Half dose of N may be applied 2 months after planting and the remaining quantity of N and K may be applied 4 months after planting. Mulching is an essential operation for high yield. Application of leaf mulch during planting and after each topdressing followed by earthing up, using a total of 20 tons of green leaves/ha, favourably modifies the soil’s physio-chemical environment resulting in increased availability of nutrients and also controls weeds. Irrigation is required when rainfall is limited. Root knot nematode (Meloidogyne incognita) and shoot borer (Dichocrosis punctiferalis) attack the crop. Leaf spot caused by Colletotrichum zingiberis and Phyllosticta zingiberi, rhizome soft rot caused by Pythium aphanidermatum and bacterial wilt caused by Pseudomonas solanacearum are the common diseases of ginger.
For vegetable and preserved ginger, the crop can be harvested in 6 months. For dry ginger, harvesting is done during December and January, about 8-9 months after planting when the leaves become yellow and shoots start lodging. The yields vary from 20-30 tons/ha for fresh ginger and it produces 20-30% of dried ginger. Yields as high as 40 tons/ha have been produced by irrigated crops.
Post Harvest Technology
For the production of dried ginger, dirt and roots are removed from rhizomes and washed in water, carefully scraped and dried in the sun for 5-6 days. The scraped or peeled ginger is known as uncoated ginger and that with the epidermis still attached as coated ginger. The rhizomes are sometimes bleached with sulfur fumes or lime water. The dried rhizomes may be powdered to produce ground ginger. In the preparation of preserved ginger, the rhizomes may be stored in brine until processed by controlled heat, cooking in syrup. Large light coloured brittle rhizomes with good aroma and little fiber fetch the highest price. Essential oil is generally obtained from unpeeled powdered ginger. Typically, steam distillation for 10-15 hours yields 1.0-2.7% oil. Ginger oleoresin is obtained by solvent extraction of powdered, dried ginger. The average yield is 4.5-6.5%. The oleoresin possesses all the aroma, flavours and pungency of ginger. It contains 20-25% essential oil and 25-30% pungent principles.