Taste of Life: How copper toxicity sparked quest for safer cooking alternatives

Copper was liable to be acted upon by almost all saline substances. It readily dissolved not only in every acid but also in alkalies and even in vegetable oils and animal fats

Cooking utensils play a vital role in shaping the flavours and techniques of regional cuisines. They reflect and shape cultural and culinary practices.

Copper, because of its malleability, ductility, and splendour, was a coveted metal for household utensils in most parts of the world. Poona was known in India and Europe for its excellent copper and brassware. (REPRESENTATIVE PHOTO)

In 1888, the Duke of Connaught and the Duchess travelled to and from Hyderabad with many staff members. The Nizam entertained the guests with royal splendour. However, during the return journey to Poona, the whole party was more or less ill, and with the exception of Dr Keith, the Duke’s surgeon, the party recovered.

Keith’s death and illness were attributed to cholera. But subsequent investigation revealed the old story – neglected cooking pots made of copper. It could be suspected that many an English traveller had died of so-called cholera in Colonial India, the symptoms of which and those of copper poisoning were remarkably alike. Vomiting, purging, cramps, and collapse were indications of both.

Copper, because of its malleability, ductility, and splendour, was a coveted metal for household utensils in most parts of the world. Poona was known in India and Europe for its excellent copper and brassware. They were sold in the markets of London, Bombay, Baroda, Indore, and Bijapur, among others. Copper vessels made in Poona were often featured at various art and craft exhibitions held in India and abroad.

Some wealthy families in Poona bought copper and brass wares from Nasik owing to their superior finish. Nasik was a place of pilgrimage, and many Hindus visited it for religious purposes. When they returned to their homes, they generally took with them several copper and brass pots as presents to relatives and friends. At the “thread” and marriage ceremonies among Hindus of the so-called “higher castes”, a set of copper, brass, or silver drinking pots and cups were given to the boy who was to wear the sacred thread or to the bridegroom.

Copper was liable to be acted upon by almost all saline substances. It readily dissolved not only in every acid but also in alkalies and even in vegetable oils and animal fats. Copper, when rubbed with a warm hand, yielded an unpleasant odour and, when applied to the tongue, a nauseous taste. Confectioners, native and European, used copper vessels to prepare syrups of orange and lemon juice since they believed that they acquired no ill taste from the metal while kept in a boiling heat, whereas, if kept cold in such vessels, they soon became impregnated with the disagreeable taste and “pernicious qualities” of copper.

William Walker, the Scottish-born Australian writer whose nom-de-plume was Tom Cringle, firmly believed that not a few deaths occurred in the ranks of European life in India from copper poison induced from copper cooking utensils. In a letter he wrote on July 31, 1862, he wondered why this “objectionable practice” was allowed when enamelled ironware, then used all over England, was plentiful, durable, cheap, and ‘worthless to the copper-cooking-pot thief of India”.

Copper cooking pots in the European kitchens of Poona attracted plenty of thieves. Cringle was grateful to the “light-fingered clan” for easing the European population of its copper pots, pans, and kettles at one tall swoop, which helped make acquaintance with “wholesome ironware, and dropped acquaintance with the doctor”.

Cringle was sure that many Europeans living in small cities and villages of Deccan had fallen victim to “copper’s poison” and cholera bore the blame. According to him, it was not even suspected in many European households that the dinner curry or Irish stew made by cooks early in the morning and stood by began to act on the metal of an imperfectly tinned pot. The oxide of copper was at once intimately mixed up for the unsuspicious recipient when loss of health and impaired digestion followed—and in bad cases, death itself, he wrote.

Copper vessels were tinned to avoid poisoning, but the tinning was usually very thin and corroded easily. Indian dishes were usually flavoured with “vegetable acids”, tamarind, tomatoes, lime juice, or vinegar, which all acted on the worn tinning. In an article published in the “English Mechanic and World of Science” on March 22, 1889, the author “Eos” mentioned how he had seen a dish of food which had been put away in a tinned copper vessel for future consumption, with a green circle on the outer edge of the congealed grease.

This “green circle” was verdigris, a common name for any of a variety of somewhat toxic copper salts of acetic acid, which ranged in colour from green to bluish-green depending on their chemical composition. Copper kettles, untinned and unprotected, were popular in the Bombay Presidency. They were used in travellers’ bungalows and boarding establishments, and verdigris frequently formed on these when acidic fruits were stewed and allowed to stand.

Domestic poisoning by means of copper was formerly advocated by the authors of cookery books, who advised that in the cooking of certain vegetables, a few half-pence should be boiled with them “to give them a fine green colour”. This was too often adopted in the preparation of pickles and preserved green fruits, the bright green colour being found to have a great attraction for consumers, and there had been numerous instances of poisoning in this way.

In 1592, at a meeting of the great senate of Bern, the wine was put into copper vessels and suspended in a well to cool it. In a few days, the legates and others who had drank were seized with violent pain in the abdomen, fever, and dysentery, and many died. In the early nineteenth century, regulations were enacted in several cities in Europe that forbade distillers, apothecaries, and others from using copper vessels unless they were tinned.

Despite warnings by doctors and sanitation officers, copper pots remained popular in Poona kitchens in the nineteenth century. European and native cooks believed that if the copper vessel was kept perfectly clean and the food prepared in it was allowed to cool in vessels not made of copper, there was not much risk of it acquiring a poisonous impregnation.

The “Poona Advocate”, on July 12, 1882, wrote of an easy method of detecting copper impregnation in pickles and preserved fruits where a clean steel needle was inserted, which after a time by galvanic action would “become coated with copper”.

“Eos” wrote about this “death in the pot”. A solder of two parts lead to one of tin was a favourite cheap admixture of the native workman. Itinerant tinners called at the houses of Anglo-Indian residents for the job, and if the solder was not examined previously, there was lead poisoning for the unsuspecting householder. He wrote that twice a month, he oversaw the operation at his house in Poona and examined the solder, telling the workman beforehand that he always did so.

Canned foods arrived in India in the mid-nineteenth century. It was soon realised that canned provisions of a cheap quality had repeatedly caused serious illness, and occasionally death, in India. They were imported; the solder used in the operation being the only portion of the contents open to suspicion.

More about this next week.

Chinmay Damle is a research scientist and food enthusiast. He writes here on Pune’s food culture. He can be contacted at chinmay.damle@gmail.com