How and why does lead chromate (a poison) find its way int0 turmeric powder (an edible spice)?
| Lead chromate | Turmeric |
Lead Chromate. C.I.77600-77603, historical dye collection of the Technical University of Dresden, Germany, Shisha-Tom via commons.wikimedia.org
Turmeric Powder. Sanjay Acharya, en.wikipedia via https://commons.wikimedia.org/
Central Food Technology Research Institute (CFTRI), India, on turmeric processing (Business Standard, 2014)
“In the conventional method of processing raw turmeric tubers for improving their appearance and colour, they are first boiled in cow dung extract and subsequently treated with an emulsion made of castor seed paste, alum and Chemichrome (a brand of lead chromate). The first treatment is neither hygienic nor aesthetic, and the latter contaminates the tubers with lead which is a cumulative poison.”
CFTRI introduces a method that uses neither cow dung nor lead chromate to prepare turmeric.
Apparently the problem of lead chromate affects several food products:
http://agmarknet.nic.in/adulterants.htm
| Lead chromate | Turmeric whole and powdered, mixed spices | Anemia, abortion, paralysis, brain damage |
A quick search using the terms “turmeric” and “lead chromate” reveals the following:
| Year From | Year To | Hits |
| 01/01/71 | 31/12/80 | 0 |
| 01/01/81 | 31/12/90 | 0 |
| 01/01/91 | 31/12/95 | 1 |
| 01/01/96 | 31/12/00 | 2 |
| 01/01/01 | 31/12/05 | 33 |
| 01/01/06 | 31/12/10 | 70 |
| 01/01/11 | 31/12/15 | 136 |
So, are we more alert now? Has the problem become more prevalent?
The CFTRI link above said it is “conventional” to use lead chromate. Surely not–must be after those pesky inorganic chemicals made their way across the world following the world wars…(see the legend to the lead chromate picture above)
How far back do “conventions” and “traditions” have to go before being called that — one generation?
Bits of history: Chromium the metal, “a thoroughly modern metal,” has been known only since 1797. Different chromium salts were commonly used in painting, but it was supposedly in early 1800s that lead chromate made its appearance.
The story about inorganic dyes and a German connection starting in the last part of the 19th century is well known.
And so to the Victorian era, when “sweet makers took advantage of this love of bright colours for sweets, especially in children, by adding synthetic chemicals to them for the first time. These included mercury sulphide (red), yellow lead chromate (yellow), copper sulphate (blue) and copper arsenite (green).”
In an interesting twist, turmeric (and lead chromate) was detected as an adulterant of custard powder in the 1850s:
| Product | Adulterants [bulk] | Adulterants [colour, taste, smell] |
| Custard powders | Wheat, potato and rice flour | Lead chromate, turmeric to enhance the yellow colour |
So it’s no wonder that lead chromate made its way to the preparation of the humble, ubiquitous turmeric. There must be “conventions” that went back before the 1800’s — or are currently used in small scale production. Processing of turmeric in Chhattisgarh, with or without cow dung and nary a mention of lead chromate, is described in this thesis from Indira Gandhi Krishi Vidyalaya, Raipur (2015)
When, and where, did the addition of lead chromate start? How far did it spread? How find out? ICAR records? Wealth of India? Trade records? Grandparents, diaries, letters?