When it comes to food, “natural” is usually a byword for “good”. But some natural products are a bit disgusting. For example, a natural flavouring called castoreum is a thick, odorous secretion obtained from the anal glands of beavers. It is used to give a vanilla flavour to some dairy products and desserts.

When it comes to food, “natural” is usually a byword for “good”. But some natural products a