Flavour enhancers are used to bring out the flavour in a wide range of foods without adding a flavour of their own. For example, monosodium glutamate (E621), known as MSG, is added to processed foods, especially soups, sauces and sausages.
Flavour enhancers are also used in a wide range of other foods including savoury snacks, 
prepared meals and condiments. Salt, although not classed as a food additive, is the most widely used flavour enhancer.
Monosodium glutamate (MSG)
Monosodium glutamate is the sodium salt of the naturally occurring amino acid glutamic acid. This amino acid is one of the most abundant in nature, being an important component of all proteins. Monosodium glutamate, has been used as a seasoning or flavour enhancer, since it was first isolated from seaweed more than a century ago and is now recognised as the most pure example of umami or savoury taste. The body treats glutamate in exactly the same way whether it comes from the food we eat or from seasoning.
MSG not only adds a umami character to food but can also be used to reduce the salt content. For the latest information about the science about glutamate and umami taste. It was suspected by some people of being the cause of ‘Chinese restaurant syndrome’, where people suffer a hot flushing reaction after eating food containing MSG. However, tests on people who claim to be susceptible have never been able to confirm that there is a link, as this scientific review explains.
