Processing

Cleaning:
• Harvested turmeric rhizomes are cleaned off mud and other extraneous materials adhering to them and subjected to curing within 2-3 days after harvest so as to ensure the quality of the end product.
  Boiling:
• Fingers and mother rhizomes will have to be boiled separately. Boiling is usually done in MS pans of suitable size.
• Cleaned rhizomes (approximately 50 kg) are taken in a perforated trough of size 0.9 m x 0.55 m x 0.4 m made of GI or MS sheet with extended handle.
• The trough containing the rhizomes is then immersed in MS pan (1 m x 0.62 m x 0.48 m) containing clean water sufficient to immerse the rhizomes.
• The whole mass is boiled till the rhizomes become soft.
• The correct stage of cooking can be judged by piercing a wooden needle through the rhizome.
• If the rhizomes are properly cooked, the needle will pass through the rhizome without resistance.
• The cooked rhizomes are taken out of the pan by lifting the trough and draining the solution into the pan.
  Drying:
• The fingers are then dried in the sun by spreading them as a thin layer on bamboo mats or drying floor.
• Artificial drying at a maximum temperature of 60^oC gives a bright coloured product than that of sun drying especially for sliced turmeric.
  Curing of Turmeric:
• Use turmeric boiler TNAU model 100 kg capacity especially for commercial growers and steam boil for 60 minutes.
• This method reduces drying time to 10 days and improves quality and cleanliness.

Polishing

• In order to smoothen the rough and hard outer surface of the boiled dried turmeric and also to improve its colour, it is subjected to polishing.

Hand polishing:
• The method of hand polishing is simple, which consists of rubbing turmeric fingers on hard surface or trampling them under feet wrapped in gunny bags.
• The improved method is by using hand-operated barrel or drum mounted on a central axis, the sides of which are made of expanded metal mesh.
• When the drum filled with turmeric is rotated, polishing is effected by abrasion of the surface against the mesh as well as by mutual rubbing against each other as they roll inside the drum.
  Machine polishing:
• This method consists of an octagonal or hexagonal wooden drum mounted on a central axis and rotated by power.

• This is obtained by the solvent extraction of the ground spice with organic solvents like acetone, ethylene dichloride and ethanol for 4- 5 hours.
• It is orange red in colour. Oleoresin yield ranges from 7.9 to 10.4 per cent.
• One kg of oleoresin replaces 8 kg of ground spice.