Why is silver foil used in Indian confectionery and sweets?

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Many years ago I returned from an Indian vacation carrying a box of Indian confectionery for my friends at the Midwestern company where I worked.  Things like barfi, kalakand and such, solidified milk based creations with sugar and other additives.  This was the early nineties, Indian food was not common in Minnesota, and it was likely their first exposure to Indian sweetmeats.  One of them looked with some doubt at the thin silver foil that covered one of these confections (it is meant to be eaten along with the piece).  Eventually his curiosity got the better of him and he popped it in.  But his hesitation got me thinking.

Silver foil, called varak, vark or chandi ka waraq,  has been used in all types of Indian sweets made with milk, dates, and nuts for at least a few hundred years and India uses up about 13 British tonnes of silver foil every year for this purpose.  Most likely this is because the antibacterial properties of silver has traditionally helped increase the shelf life of the confections.

This is not only an Indian thing.  More than a hundred years ago, milk would be preserved in the West by throwing in a silver coin.  Before penicillin came along, silver was part of wound dressings used in WWI.  The fact that silver, along with other metals such as copper and zinc can destroy living cells was figured out around 1893.

Why silver acts this way is not known for sure.  There are a few theories.  One is that the silver strips away and reacts with elements like sulfur present in bacterial cell membranes.  This affects the ability of the bacteria to respire, or to absorb energy so that it eventually dies.

Muslim artisans from Hyderabad specialize in hammering waraq out in micrometer thick foil between pieces of leather. While waraq  is supposed to be 99.9% silver, today there is likely far more danger from the spurious alloying of the silver—there are reports of this happening frequently.  The good news is that alloying silver reduces its ability to be “worked” into very thin sheets so there is a limit to the extent of contamination possible.

Visiting a regular, middle class Indian confectionary in a large Indian city can cause some anxiety to the tourist.  There are usually flies hovering around inside the glass cases where the food is stored.  Indian sweets however are unlikely to give stomach infections.  Quite aside from the silver foil, which not all confections have, the high sugar content can dehydrate and kill bacteria, curbing their growth.  Syrupy confections such as rossogollas are particularly effective in this regard.