Saltpetre

Saltpetre is a chemical known as potassium nitrate, and has been used as a preservative in brines and dry salt curing mixtures for hundreds of years. Not only does saltpetre act as a preservative, but it also adds a rosy colour to foods, most commonly seen in bacon, ham, salt beef and salami. In France, a pinch of it is added to pâté to give it an attractive colour.