Glycine and its sodium salt

Glycine is the simplest of all amino acids — a fundamental building block of proteins found in virtually all living organisms. When used as a food additive under the designation E640, it serves as a flavour modifier, providing a mild sweet-savoury background note that can soften bitter or acidic tastes and contribute to the roundness of flavour in complex food systems. Its sodium salt, sodium glycinate, functions similarly. Both forms are used in seasonings, instant soups, condiments, and flavoured snacks.

JECFA evaluated glycine in 1975 and assigned a "not specified" ADI, reflecting its status as a normal dietary amino acid that is synthesised by the body and consumed continuously through dietary protein. Glycine is involved in the biosynthesis of haem, glutathione, collagen, and bile acids, and is completely metabolised through established pathways. No toxicological concern exists at levels used in food flavouring.

Glycine is approved in the EU and across most global food markets as a flavour enhancer and acidulant. It can reduce the perception of bitterness from other ingredients and is used in Japan and elsewhere as a broad flavour modifier in seasonings and processed foods. Unlike glutamate-based flavour enhancers, glycine does not produce a pronounced umami taste but rather a background sweetness and mild savoury note. On ingredient labels it appears as glycine, sodium glycinate, or E640. No known adverse effects have been associated with its use as a food additive, and it is generally well tolerated including by individuals sensitive to other amino acid additives.