The Centre’s food safety authority on Wednesday asked the states to ensure that the food-grade silver leaf used on sweets is not made using material of animal origin, in line with the authority’s notification two years ago.

The Food Safety Standards Authority of India, citing information brought to its notice, said “some unscrupulous food business operators are still involved in manufacturing food-grade silver leaf” through processes that use materials of animal origin.

Food-grade silver leaf sheets, also called chandi-ka-warq, was traditionally made by placing silver inside the intestines of a cow or a buffalo for several hours and then hammering it over a granite stone.

The FSSAI had in July 2016 issued a notification prohibiting the use of animal materials. It has now asked food safety commissioners in all states and Union territories to conduct surveillance and ensure compliance.

Delhi High Court had in July 2017 stayed the July 2016 notification on a petition from the traditional manufacturers of silver leaf, who had claimed that more than 150,000 workers would be “rendered jobless”.

But the court vacated the stay earlier this year after the FSSAI told it about alternative manufacturing processes that involve beating the sheets using specially treated paper and polyester coated with food-grade calcium powder.

The 2016 notification had also imposed quality standards specifying that food-grade silver leaf sheets should be free from creases and folds, with the silver foil weighing up to 2.8g per square metre, and have silver content of minimum 999/1,000 fineness.

A 2005 study by scientists at the Industrial Toxicology Research Centre, Lucknow, had found that only 46 per cent of 178 samples of silver foil analysed adhered to the desired purity of 99.9 per cent.