Mustard seeds are native to Southern Europe and Western Asia. Yellow mustard seeds are generally used in pickling spice mixes and marinades. Yellow mustard seeds also assist in flavouring and emulsifying salad dressings. Mustard seeds have virtually no aroma. Characteristic mustard "heat" is released only when the enzyme myrosinase is activated in the presence of (cold) water. However, frying in oil or dry roasting seeds does not activate myrosinase (heat) resulting in an aromatic flavour. For this reason, many curries display the nuttiness of mustard without the intense heat. Brown seeds are slightly more pungent than yellow seeds and are generally used in Indian dishes e.g. curries, Dahl’s.