麩胺酸鈉 (MSG或味精) 是一種由胺基酸組成的麩胺酸內的鈉鹽。番茄、芝士酸水解植物蛋白、自溶酵母、水解酵母，酵母抽提物、乳清蛋白、大豆萃取物和分離乳清蛋白等也包含麩胺酸鈉。但是，麩胺酸鈉也是增味劑和添加劑。在1908年，池田菊苗教授為了證實麩胺酸能提升湯的味道，他運用提取和結晶的方法從含豐富谷氨酸的海帶清湯中分離出麩胺酸。池田教授將這種產物命名為麩胺酸鈉，並為生產MSG申請專利。其後那年便開始了商業化生產。

現在只要把碳水化合物、甜菜、甘蔗或糖蜜發酵便能產生麩胺酸鈉。美國食物和藥品管理局（FDA）指出，麩胺酸不含有麩質；即是患有乳糜瀉的人也不會對MSG產生反應。

1995年，美國實驗生物學學會聯合會（FASEB）編撰了一份報告，結論為MSG並不會構成危險。雖然有些人在淨攝入3克MSG時會出現短期而較輕的反應，如頭痛、肢體麻木、潮紅、刺痛、心悸、嗜睡，但因大多數食品的味精含量低於0.5克，所以症狀並不常見。此外，因為現時沒有發現任何對MSG有固定的反應或病症，大部份科學家認為對於MSG有敏感反應的人是非常罕見的。雖然如此，如果對於進食MSG後感到不適者應該盡量避免服用和留意食物標籤 (如“水解大豆蛋白”和“自溶酵母”) 不吃預先包裝，但選購新鮮的食物。

作者: 李德瑩, 實習營養師

Monosodium Glutamate (MSG) is the sodium salt commonly found in package food. It occurs naturally in hydrolyzed vegetable protein, autolyzed yeast, hydrolyzed yeast, yeast extract, soy extracts, protein isolate, and especially tomatoes and cheeses. However, MSG can be a flavor enhancer and additives. In 1908, Kikunae Ikeda, who is a Japanese professor, extracted and crystalized glutamate from a glutamate-rich seaweed broth and determined that glutamate was providing the savory taste to the soup. He then created a patent to produce MSG and started the commercial production in the following year.

Today, instead of extraction and crystallization, MSG is produced by the fermentation of starch, sugar beets, sugar cane or molasses. According to US Food and Drug Administration, glutamate or glutamic acid do not contain gluten; a person with Celiac disease will not react to the MSG.

The report of Federation of American Societies for Experimental Biology (FASEB) concluded that MSG is safe in the 1995. Some transient and generally mild symptoms, such as headache, numbness, flushing, tingling, palpitations, and drowsiness may occur in some sensitive individuals who merely consume 3 grams or more of MSG without food. However, a typical serving of a food with added MSG contains less than 0.5 grams of MSG.

Since studies have not found any fixed or regular condition to MSG, most scientists agree that people who are sensitivity or allergic to MSG are extremely rare. Nonetheless, people who think they have problems with it should eat fresh food and avoid eating pre-packed food contains MSG; labelled as "hydrolyzed soy protein" and "autolyzed yeast".





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