Early chefs in Chinatown had given MSG the nickname of “shi fu”, the venerable title for a master or teacher.
As a young student of medicine around 1980, I was bemused to learn of an illness known as Chinese Restaurant Syndrome. Apparently following Chinese food, some diners suffer from chest pain radiating to their arms, sweating, palpitations and general weakness. These are similar to symptoms of a heart attack and created panic, but are usually short lived and leave no lasting harm.
The syndrome was first described in 1968 by Dr Robert Ho Man Kwok in the respected New England Journal of Medicine. Similar reports soon followed suit and suspicions fell upon Monosodium Glutamate (MSG), a common ingredient of Chinese restaurant food. The reaction to MSG begins in 10 to 25 minutes and lasts from 45 minutes to 2 hours. Researchers noted that the amount of MSG that may be consumed before unpleasant effects set in varies widely from one individual to the next. The ballpark figure was estimated at five grams –ordinary dishes would contain sufficient quantities. The syndrome is diagnosed by enquiry about the symptoms. Most sufferers do not require treatment and do not have permanent effects.
Interestingly, Dr Kwok added that he had never experienced such a problem in his native China. Various surveys in North America have shown between 1 to 7 per cent of population are affected by this syndrome. However successive researchers have been unable to pinpoint MSG as the cause.
As the name implies, monosodium glutamate is formed from processed free glutamic acid (78%) and sodium salt (22%). The processed free glutamic acid is responsible for the unpleasant reaction. Glutamic acid is an amino acid –a building block for proteins –that occurs naturally in foodstuffs such as vine-ripened tomatoes, mushrooms and crab. Many proteins are inherently tasteless, but when fermented the amino acids produce various tastes, such as in soy sauce, cheese and anchovies.
The tastes of ordinary meat, poultry and fish come from various amino acids which include glutamic acid. In addition to the four basic tastes – sweet, sour, salty and bitter – a fifth taste has been recognised as “umami”, a broth-like or savoury taste. Umami has been revisited in the Sunday Times by the renowned chef Heston Blumenthal: “It’s a bit like introducing a new colour that we have been looking at all our lives but never recognised before.”
Most meats consist of 11 to 22 per cent by weight of glutamic acid. The butcher’s art of dry ageing steaks releases glutamic acid and another compound called inosine monophosphate (IMF). The particular flavours of different meats are accounted for by varying proportions of glutamic acid and IMF.
Condiments in Chinese cooking such as soya sauce and yellow bean sauce also owe their flavour to fermentation that produces glutamic acid. Besides Chinese food, MSG can be found in sauces, soups, gravy, pre-cooked meals and dried foods. According to an American physician George Schwartz, MSG is the third most popular spice – after salt and pepper –it is present in over two hundred and fifty ordinary items stocked by supermarkets.
MSG is said to make food flavours more intense, and enhance the taste of meat in particular. However, this effect reaches a ceiling at 60mg/kg. Concentration higher than this level makes food less palatable.
MSG was discovered just over a century ago. In 1908, Professor Kidunae Ikeda (池田菊苗), a biochemist at Tokyo Imperial University, was served a vegetable and tofu soup by his wife. Scientific curiosity prompted him to ask her about the secret behind such a delicious broth. His wife simply showed him dried seaweed, a heavy kelp called kombu. Ikeda eventually identified that the seaweed contains glutamate and that this produces the umami taste. The secret ingredient was born and quickly became popular.
Professor Ikeda found that meat, tomatoes as well as seaweed owe their flavours to one factor in common. In particular, Japanese seaweed or kombu has a high concentration of glutamate, about 1000mg per 100g.
At the time, a businessman named Saburo Suzuki (鈴木三朗助) was trying to extract iodine from kelp. On hearing about Professor Ikeda’s discovery, he was inspired to produce glutamate instead. Suzuki and Ikeda realised that the 0.1-0.2 grams they could extract from 10kg of kelp was not commercially viable. They turned to the much cheaper soybean and wheat which also contained glutamate. Soon, the product Ajinomoto (meaning element of taste) was launched.
Glutamic acid dissolved in the form of glutamate gives rise to the umami taste. Salt forms such as monosodium glutamate dissolve more easily than glutamic acid crystals, which make them ideal flavour enhancers.
Interestingly, human breast milk also contains high levels of glutamate –ten times that of cow’s milk. Experts believe that the umami flavour, as well as the sweet taste of lactose, entices babies to feed.
Concerns were raised about the safety of MSG after scientists found that young animals that had MSG in their diets developed brain abnormalities, causing hormonal imbalance and obesity. This led to the exclusion of MSG from baby food in the 1970s.
Many rumours abound concerning effects of MSG – it stops children’s skeletons growing, causes hair to fall out, turns cola or beer into aphrodisiac, or predisposes men to produce male offspring.
Actually, the human body normally contains an amount of glutamate, and in fact depends on glutamate for conducting commands in the nervous system and for memory. Some scientists worry about over-stimulating the brain by ingesting large quantities of MSG in a single meal.
However, scientific studies led by Dr Andrew Saxon of the Allergy and Immunology Department at University of California found no connection between the Chinese restaurant syndrome and MSG.
The term ‘food additive’ often raises anxiety among consumers. The United States Food and Drug Administration has registered over three thousand additives. In fact, many of these are everyday ingredients such as spices, yeast and vanilla. Some items are regulated more tightly than others. MSG belongs to the category GRAS (generally recognized as safe), and its usage is exempt from control.
A contrary view is that MSG may actually resolve a health problem. People are often advised to cut down on their salt intake. Experiments have found that a soup becomes tasty only when salt concentration reaches a certain level. With addition of MSG, salt usage can be reduced by two-fifths.
Glutamic acid was known during the Roman Empire, when salted fish was fermented into a sauce. This flavour enhancer helped Romans save consumption of precious salt. (Wikipedia)
Within the European Union, food labelling law requires ingredients to be listed, either by name (MSG or glutamic acid) or by their E numbers (E620 to E625). The EU also prohibits addition of MSG to certain products such as milk, fruit juice and chocolate.
Many consumers believe that MSG is a synthetic chemical and harmful, whereas chicken stock cubes are manufactured from chicken meat and nutritious. During the Beijing Olympics in 2008, the Brazilian team specified that their meals be free of MSG. In fact, chicken stock often contains up to 40% MSG as well as other flavourings.
Experienced chefs have revealed several taboos when using MSG:
• High temperature – temperatures above 90C cause chemical change in MSG which may become toxic. Hence it is best to add MSG just before cooking is completed. For the same reason, it is not a good idea to add MSG to marinades.
• Low temperature – MSG does not dissolve well in cold water, to use on chilled dishes it should first be dissolved in warm water.
• Alkaline foods – MSG undergoes chemical change in alkaline solutions to produce an odorous substance, and thus is unsuitable for alkaline food such as preserved cuttlefish.
• Acidic foods – MSG cannot dissolve properly in acidic liquids.
• Sweet dishes – MSG will suppress the sweetness and result in an unpleasant taste.
• Overuse – Excessive amount of MSG results in a salty and bitter flavour.
• Eggs – Eggs themselves contain abundant glutamic acid, which combines with cooking salt to become MSG. Additional MSG is unnecessary and may worsen the taste.
The Chinese method of MSG manufacture was invented during the heady days of Shanghai in 1921. A chemicals entrepreneur Wen-Chu Wu (吳蘊初) discovered a process of producing glutamate from gluten, and called it wei-jing (味精), meaning essence of taste. His MSG factory in Hong Kong and its products have been well known for over 70 years.
MSG is such a major industry that recently the Hong Kong Customs and Excise exposed an illicit factory with 1,400 sacks of counterfeit MSG.
Early chefs in Chinatown had given MSG the nickname of “shi fu”, the venerable title for a master or teacher. In their view, without the master’s presence not much could be achieved. A number of restaurants now declare that their menus are free of MSG. Experienced cooks are of the opinion that their clientele have been accustomed to a certain taste, and may find the dishes lacking in flavour if MSG were totally withdrawn. However, some chefs have replaced MSG with stock cubes or bouillon.
In 2007, the Michelin-starred chef Marco Pierre White caused a stir by admitting that he also used stock cubes in his recipes.
It seems therefore, while Chinese restaurant syndrome has gone, MSG or its derivatives are here to stay!
London, October 2011
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