Chemical Engineering in Daily Life – Question 24: When should monosodium glutamate be added when cooking? Standard answer already available
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This post was last edited by yjqin1 on 2015-9-9 08:24. Ever since Japan invented monosodium glutamate (MSG), people in China have eaten it in large quantities. Actually, not really; in the 1970s, monosodium glutamate wasn’t that common yet. I remember when I was young, I would secretly put a little MSG in a teaspoon, add some water to dissolve it, and then taste it – it was very savory. I remember wanting to try using \"banana oil\" as a flavoring agent for dumplings, but it’s extremely irritating; as soon as the small bottle is opened, it’s almost impossible to keep your eyes open. I guess it’s something like isopentyl acetate or similar. My grandfather was an old farmer from Tangshan, Hebei; he was quite fashionable – he used monosodium glutamate and banana oil, and ate seaweed and pickled vegetables. What is monosodium glutamate? During the Qing and Republican periods, the Beijing-Tianjin area was the domain of Shandong cuisine; even the imperial dishes were prepared by master chefs from the Jiaodong Peninsula in Shandong, and the taste was truly excellent. Why? Gourmets all say that the food prepared by handsome chefs who move with grace and flair when cooking is the most delicious. Why? I don’t know; anyway, that’s what people say. However, there were also some skilled workers from Penglai in Yantai who were beaten mercilessly by their employers in the capital, to the point of being paralyzed. Why? At that time, there was no monosodium glutamate, but these master chefs used a natural substitute for it – dried sea cucumber powder. They secretly hid it in their sleeves, slipping in some of it discreetly among the larger items. What is a sea asparagus? When the princes and wealthy merchants of that time learned the truth, how could they not become anxious? What is a sea asparagus? Do you know? Go online and watch the video; it’s absolutely disgusting. Nowadays, people turn away at the mention of monosodium glutamate; some avoid Chinese food, while others can detect it even in small amounts in their meals. How to use monosodium glutamate correctly? For example, when cooking home-style dishes such as pork tenderloin stir-fried with carrots (sweet) and peppers, when should monosodium glutamate be added? 1. First, marinate the cut sirloin in cooking wine, five-spice powder, soy sauce, vinegar, salt, and cornstarch, then cook it slowly ； 2. Add when stir-frying the sirloin ； 3. Add when stir-frying vegetables ； 4. Turn off the heat and add the ingredients before serving. 5. Turn off the heat, add monosodium glutamate, and stir for a while. Please make your choice.
5. Stop the heat and stir-fry for a while after adding monosodium glutamate.
5. Stop the cooking, add monosodium glutamate and stir-fry. Because monosodium glutamate decomposes at high temperatures
It is said that high temperatures can also turn it into harmful substances
Standard answer: Monosodium glutamate is the monosodium salt of glutamic acid, which is an amino acid containing two carboxyl groups. Its salt thermal stability is good; when heated at 100°C for half an hour, only 0.3% of it dehydrates to become inedible and non-toxic sodium pyroglutamate (assuming that this reaction follows first-order kinetics, the loss rate of glutamic acid and other amino acids during 10 hours of slow cooking will also not exceed 3%). However, basic amino acids with two amino groups do not have such good thermal stability; arginine, lysine, and histidine are less stable. I used them to create membranes that facilitate the separation of carbon dioxide back then, so I have a strong memory of that experience. So we chemical industry professionals shouldn’t turn pale at the mention of monosodium glutamate. When using monosodium glutamate, it is important not to leave it at high temperatures for too long (chemical reaction kinetics follow the Arrhenius equation to a large extent). Given the dietary habits of the Chinese people, only methods such as stir-frying, frying, deep-frying, roasting, as well as cooking and steaming in a pressure cooker involve high temperatures of over 100 degrees Celsius. For stir-frying, the pressure of gas used by people in China is much higher than that in Europe and America, resulting in a very intense flame. Therefore, I suggest not cooking for too long, and making sure there is still some water (juice, liquid) in the pan. At that time, the temperature of the inner surface of the pot could be >100°C. So, all netizens should now have the correct answer. At the same time, it is also not recommended that netizens consume various grilled foods frequently; there’s no need to explain why. Eating barbecued food and raw animal products is a sign that Europe, America, and Japan have not fully evolved; we must not regress.