本文選自雅思聽力Section 4，難度較大

Summary:味精是許多人在烹調(diào)的時(shí)候會(huì)使用的調(diào)料，但卻很少有人了解它的歷史。實(shí)際上，許多種調(diào)料在進(jìn)入人類的廚房之前都經(jīng)歷了一個(gè)復(fù)雜而又曲折的過程。味精也是一樣，它最先是由人們?cè)谝环N還槽中提煉出來的。

HINTS
kombu
glutamate
MSG

全文聽寫，英式拼法

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But it wasn't until 1908 that the ingredient in kombu which was responsible for the improvement in flavour was actually discovered to be glutamate by scientists working there. From 1908 until 1956, glutamate was produced commercially in Japan by a very slow and expensive means of extraction. It was in 1956 that the speed of the process was improved, and industrial production increased dramatically and still continues to increase to this day. In fact, hundreds of thousands of tonnes of MSG are produced all over the world today.