The dosage should not be excessive. For each person, the daily intake should not exceed 120 mg per kilogram of body weight. It is best for infants under one year of age not to consume MSG. Only a small amount is needed during cooking to achieve the purpose of enhancing flavor.
It should not be used in strongly alkaline foods. The sodium in monosodium glutamate is highly reactive and can easily undergo a chemical reaction with alkali, producing disodium glutamate, which has an unpleasant odor and loses its seasoning effect. Therefore, strongly alkaline dishes such as kelp and squid should not have MSG added.
MSG should not be used in sour dishes. Because MSG does not dissolve easily in acid, the higher the acidity, the lower the solubility, and adding MSG will be ineffective.
It should not be added too early when stir-frying. MSG should generally be added when the dish is almost cooked or just after it is taken out of the wok. At this time, the temperature of the dish is around 70-90°C, which is the optimal temperature for MSG dissolution and the flavor is the strongest. Conversely, when added at high temperatures, if the temperature exceeds 120°C, the monosodium glutamate in MSG will turn into caramelized monosodium glutamate. Caramelized monosodium glutamate has no umami flavor and is also somewhat toxic. The temperature of fried food is generally higher than 120°C.
It should not be used as a filling. When used as a filling, whether steamed or boiled, it will be subjected to continuous high temperatures, causing the MSG to denature and lose its seasoning effect.
When making cold dishes, it is not advisable to add both soy sauce and MSG, as this will cause the umami flavor to disappear.
MSG should not be added directly to cold dishes; it must first be dissolved in boiling water. MSG can only fully dissolve above 70°C. The temperature of cold dishes is low, and adding MSG directly does not dissolve easily. If it is first dissolved in a small amount of warm water and then poured over the cold dishes, with a light toss, the effect is very good. Furthermore, using powdered MSG instead of crystalline MSG for cold dishes is easier to dissolve and mix, resulting in a better umami-enhancing effect.
MSG should also not be used for ingredients that are already very delicious (such as mushrooms, shiitake mushrooms, chicken, beef, fish and shrimp from rivers and seas, or especially fresh vegetables), because they contain inosinate and other nucleotides and have their own natural umami flavor. Adding MSG can actually worsen the taste.
Dishes consumed by mothers within three months after childbirth and by infants should not contain excessive MSG. This is because the monosodium glutamate in MSG can enter an infant's body through breast milk or food, where it will specifically bind with zinc in the infant's blood to form zinc glutamate, which is not absorbed or utilized by the body and is excreted in urine, leading to zinc deficiency in infants.