Saltpetre

Saltpetre is an old name for potassium nitrate, KNO₃, one of the ingredients in improvised explosive devices. It has been valued for hundreds of years for its preservative impact. In reality, the colouring element is the closely related nitrite – KNO₂ – a fact that was discovered only in this century. It is actually the nitrite which turns meat pink, and it is this rosy colour which understandably affects our perceptions of the food. Would ham be as nice if it was grey? However, nitrite also plays an important role in limiting the growth of the bacteria which cause food poisoning, most notably clostridium botulinum, responsible for botulism which, while fortunately rare in these days of refrigeration, can be fatal.