Food Safety Focus (204th Issue, July 2023) – Article 1
Glutamate in Your Kitchens
Reported by Ms. Sosanna WONG, Scientific Officer,
Risk Assessment Section, Centre for Food Safety
In 1908, Kikunae Ikeda, a Japanese professor, extracted glutamate from a seaweed broth and determined that glutamate provided a savoury taste to the broth. He also noticed that the taste of the broth was distinct from sweet, sour, bitter, and salty and named it umami, the fifth taste. Since then, glutamate, generally in the form of monosodium glutamate (MSG), has been commercially produced and can be found in kitchens where chefs and home cooks often use to enhance flavour of their dishes.
What are MSG and Glutamates?
MSG is a white crystallised, odourless sodium salt of glutamic acid, one of the most abundant amino acids found in nature and produced by living organisms including humans. To date, various salts (e.g. potassium, calcium, magnesium and sodium) of glutamic acid (collectively known as "glutamates") have been added to food as flavor enhancers. Various foods such as seasonings and condiments may also contain glutamates from natural or artificial sources. The commercial production of MSG uses fermentation technology to convert sugar sources to glutamates (Figure 1).
Owing to its ubiquitous presence in foods, the dietary exposure to glutamates in adults is extensive through natural or man-made sources:
(1) Natural sources: (i) "bound" glutamates that occur as proteins in almost all food such as milk, meat, poultry, fish, vegetables and mushrooms; and (ii) "free" glutamates (i.e. not bound to proteins) present in tomatoes, mushrooms, yeast extracts, fermented fish sauce and fermented/hydrolysed protein products (such as soy sauce), accounting for the savoury flavour of these foods; and
(2) Man-made sources: "free" glutamates added to the diet as salts of glutamic acid such as MSG.
Free glutamates can bind to specific receptors on the tongue and induce the umami flavor, whereas bound glutamates cannot bind to the receptors to induce the umami flavour. Natural glutamates and those artificially produced are chemically indistinguishable and both sources of glutamate are metabolised in the same way in our bodies.
Figure 1. MSG is produced by the fermentation of sugar sources
According to the U.S. Food and Drug Administration (FDA), an average adult in the U.S. consumes approximately 13 grams of glutamate each day from the protein in foods, while the intake of added MSG is estimated at around 0.55 gram per day. Other studies show that among the European population, the average MSG consumption represents between 6 and 12% of total glutamate intake. In summary, the intake of free glutamate from food additives only contributes to a small proportion of the total intake of glutamates from all sources.
Safety of MSG
The Joint FAO/WHO Expert Committee on Food Additives allocated an acceptable daily intake "not specified" to glutamic acid and its salts, meaning that their use as food additives does not represent a health concern. The FDA of U.S. considers the addition of MSG to foods to be "generally recognised as safe". According to the Codex Alimentarius Commission, MSG can be used in foods in general when used in accordance with the principle of Good Manufacturing Practice (GMP), that is, the quantity of MSG added to food shall be limited to the lowest possible level necessary to accomplish the desired effect.
Since the late 1960s, MSG has been claimed to be the cause of a range of adverse reactions in people who have eaten foods containing the additive. However, international scientific assessments have concluded that available evidence does not establish a causal relationship between the consumption of MSG and the development of symptoms such as headache, numbness or tingling in the back of the neck and flushing.
Like table salt, MSG also contains sodium. While sodium is an essential nutrient necessary for the maintenance of plasma volume, acid-base balance and normal cell function, excessive sodium intake is linked to non-communicable diseases, including elevated blood pressure. In general, salt consumption can be reduced by using less table salt and sodium-containing food additives.
How can I Tell if MSG is Present in My Food?
Under the local labelling regulation, if MSG is added to prepackaged food, the requirement is to list out its specific name (i.e. monosodium glutamate) or identification number under the International Numbering System (INS) (i.e. 621) together with its functional class (i.e. flavour enhancer) in the ingredient list on the food label. Ingredient labelling also applies to other added glutamates (i.e. additives designated 620 – 625).
Advice to Food Businesses
- Use in accordance with GMP to limit the quantity of MSG to the lowest level for flavour enhancement should it be added to food.
- Observe the labelling requirement of food additives including MSG.
Advice to the Public
- To reduce sodium intake, consider using herbs and spices (e.g. chili, ginger) and glutamate-rich ingredients (e.g. tomato, mushroom) to enhance the flavour of food.
- Read the food label to make informed choices.
- Ask the staff of restaurants if MSG is used in food if you want to avoid it.