Polished turmeric has been rubbed after drying to remove the rough outer skin and root hairs, leaving a smooth, brighter finger. Unpolished turmeric has been boiled and dried but not rubbed, so it keeps a dull, scaly surface.
Polishing improves appearance and cleanliness and slightly reduces weight. Whether you need it depends on whether you sell whole fingers or grind them.
Because polishing removes skin, it also lowers the soil and dust carried on the surface. That shows up in lab results for ash and acid-insoluble ash.
How turmeric is processed
Turmeric goes through four main steps after harvest. Some lots are polished once and some twice, and double-polished fingers are smoother and brighter.
- Harvest: rhizomes are dug, cleaned of soil and separated into fingers and bulbs.
- Curing: the rhizomes are boiled or steamed until soft. This sets the colour and helps even drying.
- Drying: the cured rhizomes are dried in the sun or in dryers until hard.
- Polishing: the dried fingers are rubbed in rotating drums, by hand or by machine, to remove skin, scales and root bits.
Polished, unpolished and coloured
Whole fingers reach the market in three finishes. Coating with turmeric powder is a traditional practice in some markets. The risk is what else goes into the coating. Lead chromate has been used to make turmeric look brighter in parts of South Asia, and it is toxic. Read how to check turmeric for lead chromate before you buy coated fingers.
- Unpolished: rough, dull and darker on the outside, with more skin and dust. Lower cost.
- Single or double polished: smoother, cleaner and more even in colour. The usual export standard for whole fingers.
- Coloured or coated: polished fingers dusted with turmeric powder, sometimes mixed with water or other agents, to make them look bright yellow.
Which one to buy
- Whole fingers for retail: polished, and say in the spec that no colouring or coating is allowed unless you ask for it.
- Grinding into powder: polished is cleaner and gives fewer skins and less dust in the powder. Unpolished can work if your spec on extraneous matter and ash is met.
- Extraction: the finish matters less than curcumin and contaminant levels.
Points for your spec
- State polished or unpolished, and single or double polished if it matters.
- State whether any coating is allowed and with what.
- Set limits for moisture, extraneous matter, total ash and acid-insoluble ash, which picks up soil and sand.
- Test lead and chromium on every lot, plus curcumin by an agreed method. See what curcumin content to ask for.
Where we come in
We see the curing, drying and polishing at the processor's unit, check whether any coating is applied, and have lot samples tested for lead, chromium and curcumin at an NABL-accredited lab. To plan a turmeric order, ask for a free sourcing review.