Turmeric (Curcuma longa L), an ancient and sacred spice from India, also known as ‘Indian saffron’, is an important commercial spice crop. It is used in varied forms - as a condiment, flavouring and colouring agent and as a principal ingredient in Indian culinary. Known to have anti-cancer and anti-viral properties, Turmeric is a sought after ingredient in the drug industry and cosmetic industry. 'Kum-kum', a by-product of turmeric, is used by Indian women to make a distinctive mark on the forehead and is used as offerings at religious and ceremonial occasions. The increasing demand for natural products as food additives has led to the popularity of turmeric as a food colorant.
The curcumin content in Indian Turmeric is one of the highest and is thus considered as the best quality turmeric. India is the largest producer and exporter of turmeric in the world, followed by Thailand, Taiwan, Central and Latin America.
Botanically called Curcuma longa, Turmeric belongs to the Zingiberaceae family (the same family as ginger). It is the rhizome or the root of Turmeric that is used. The plant grows from the rhizome and the leaves are broad, long and bright green in colour. It does not have a well-defined stem, a pseudostem that is shorter than the leaves. The flowers are pale yellow and are borne on spikes.
The best climate for Turmeric is a warm, humid climate. It grows in hilly areas at an altitude of 1500m from sea level. The ideal temperature ranges between 20-30 ⁰C and rainfall required is 1500 to 2250 mm per annum for Turmeric cultivation in India. It can also be grown as an irrigated crop.
Clayey soil with a large amount of humus is preferred for growing Turmeric. It can, however, also grow in sandy soil that is well-drained. Other types of soil that are suitable for turmeric cultivation are red soil, ashy loam or light black soil. It is important that water should not stagnate. Soil acidity must be neutral. Alkaline or acidic soil would harm the rhizome of turmeric plant thus impacting growth. Solarization is use of solar power to prevent the growth of pests and weeds. Solarizing the beds before turmeric cultivation can keep the disease-causing organisms under check.
Turmeric seeds are often kept beneath moist straw and left for sprouting before sowing. The sowing time in India, is typically just after the pre-monsoon showers.
A plant that needs lot of manure for growth, Turmeric rhizomes are usually covered with rotten cattle manure and then sown. They can also be covered with Trichoderma mixed compost. Powdered neem cake is mixed with soil and is applied in the pits prepared for sowing. Approximately, 1000 kgs rhizomes are needed for one acre of land unless it is being used as an inter-crop, in which case, the seed rate can be as low as 125 kgs per acre.
Generally, pure turmeric yields a quantity of 8000 to 10,000 Kgs/Ac. Under extremely favorable conditions, the yield can go up to as high as 12,000 Kgs/Ac.
Post Harvest Technology
Depending on the variety, Turmeric is usually ready for harvest within 7-9 months of sowing. While the aromatic ones mature in 7 months, the intermediate variety take 8 months and the late variety around 9 months. They are ready for harvest when the leaves and stem start turning brown and dry up progressively. Once dried, the land is ploughed, and the rhizomes are extracted. The extraction can be done by hand or by carefully lifting the clumps with a spade. The stems are cut an inch above the rhizomes. The finger rhizomes are separated from the mother rhizomes. While the finger rhizomes are cured to extract Turmeric, the mother rhizomes are usually stored as seed rhizomes for the next cycle.
Curing turmeric is a lengthy and challenging process because if not done properly the turmeric may not be extracted up to its full capacity. Also, care must be taken to ensure that no chemicals are used for processing.
Boiling and Drying
The rhizomes are boiled in water and kept for sun-drying.
Within 2-3 days of sun drying, the rhizomes are again boiled with just enough water to soak. This boiling is done in copper or earthen vessels. The rhizomes are boiled till it becomes soft. Some farmers cook in perforated baskets.
Separation from Water
The cooked rhizomes are taken out of the pan and water is allowed to drain from the Turmeric back into the pan. This water can be reused for cooking the next batch of harvested Turmeric rhizomes. Usually the mother and finger rhizomes are cured separately.
Once cooked, these rhizomes are spread under the sun on a cement floor. Sometimes, bamboo mats are used. While they are spread on the floor during daytime for sun drying, they are heaped together and covered at night so that moisture does not affect the turmeric. This step lasts around 10-15 days.
In case of artificial drying, cross-flow hot air at 60°C is used.
Polishing of Turmeric
Dried Turmeric has a rough dull colour on the scales. The outer surface is polished and smoothened out to improve the appearance. In case of manual polishing, the finger rhizomes are polished on a hard surface. An alternate technique is to use a hand-operated barrel mounted on a central axis. The barrel is filled with rhizomes and rotated. The rhizomes get polished by rubbing against each other and against the surface.
The key benefit of Turmeric for a buyer is its colour. Therefore, in a bid to attract the buyers, a suspension of Turmeric in water is added to the polishing drum during the last ten minutes. This helps to get the rhizomes uniformly coated.