本文选自雅思听力Section 4，难度较大

Summary:味精是许多人在烹调的时候会使用的调料，但却很少有人了解它的历史。实际上，许多种调料在进入人类的厨房之前都经历了一个复杂而又曲折的过程。味精也是一样，它最先是由人们在一种还槽中提炼出来的。

HINTS
MSG
Monosodium Glutamate
amino
erm

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全文听写，英式拼法

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So what exactly is MSG? Well, Monosodium Glutamate contains 78.2% glutamate, 12.2% sodium and 9.6% water. Glutamate is an amino acid that can be found naturally in all protein-containing foods, erm, so this includes food such as meat and cheese. It is widely known that Chinese and Japanese food contains MSG but many people don't seem to be aware that it is also used in foods and other parts of the world. For example it is found in commercially made Italian pizzas, in American fast food and in Britain MSG is used in things like potato crisps.