剑桥雅思7听力：Test4雅思听力Section4真题+答案+解析

　　In today's lecture, T'm going to talk about Monosodium Glutamate, or MSG, as it's morecommonly known. Now, MSG as you probably know, is a flavour enhancer which is usedparticularly in Chinese and Japanese cooking. Today I am going to explore why it is sopopular in these cuisines and, more importantly, how does it enhance the flavour of food?

　　The main reason why MSG is more commonly used in Japanese meals is tradition. For manythousands of years the Japanese have incorporated a type of seaweed known as kombu intheir cooking, as they discovered it had the ability to make food taste better. But it wasn't

　　until 1908 that the ingredient in kombu which was responsible for the improvement in flavourwas actually discovered to be glutamate by scientists working there.

　　From 1908 until 1956, glutamate was produced commercially in Japan by a very slow andexpensive 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.

　　So what exactly is MSG? Well, Monosodium Glutamate contains seventy-eight point two percent glutamate, twelve point two per cent sodium and nine point six per cent 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'tseem to be aware that it is also used in foods in other parts of the world. For example it is

　　found in commercially made Italian pizzas, in American fast food and in Britain MSG is usedin things like potato crisps.

　　So, how exactly does MSG work? Well, in the Western world, we commonly talk of four

　　'tastes", and I'm sure you're all familiar with the concepts of sweet, sour, bitter and salt. Well,in 1908, Kikunae Ikeda identified a fifth 'taste". And it is thought that MSG intensifies thisnaturally occurring 'taste' in some food. It does make perfect evolutionary sense that we

　　should have the ability to detect or taste glutamate because it is the amino acid which ismost common in natural foods.

　　John Prescott, an associate professor at the University of Chicago, suggests that this fifth

　　taste serves a purpose just as the other tastes do. He suggests that it signals to us the presenceof protein in food, in the same way that sweetness indicates that a food contains energy-givingcarbohydrates. Bitterness, he says, alerts us of toxins in the food, while sourness warns us ofspoilage and saltiness signals the presence of minerals.

　　So, what else do we know about this fifth taste. . .

　　在今天的课上，我们要讨论的是味精，它通常被称为味精。现在，味精，你可能知道，是一种增味剂，特别是在中国和日本的烹饪中使用。今天我要探讨为什么它在这些菜系中如此受欢迎，更重要的是，它如何食物的味道?

　　味精在日本饮食中更普遍使用的主要原因是传统。数千年来，日本人在烹饪中加入了一种被称为海带的海藻，因为他们发现海带能让食物变得吃。但它不是

　　直到1908年，科学家们才发现海带中改善味道的成分是谷氨酸。

　　从1908年到1956年，谷氨酸在日本通过一种缓慢和昂贵的提取方法进行商业生产。在1956年，这一过程的速度得到了改善，工业生产大幅增加，并一直持续到今天。事实上，今天全世界有成千上万吨味精被生产出来。

　　那么味精到底是什么?味精含有78.2%的谷氨酸，12.2%的钠和9.6%的水。

　　谷氨酸是一种氨基酸，可以在所有含蛋白质的食物中自然找到，所以这包括肉和奶酪等食物。

　　众所周知，中国和日本的食物中都含有味精，但许多人似乎没有意识到世界其他地方的食物中也含有味精。举个例子

　　味精存在于商业制作的意大利披萨、美国快餐和英国薯片中。

　　那么，味精究竟是如何起作用的呢?嗯，在西方世界，我们通常说四个

　　“味道”，我相信你们都熟悉甜，酸，苦和盐的概念。1908年池田菊苗(Kikunae Ikeda)发现了第五种“味道”。人们认为味精能强化某些食物中自然产生的“味道”。从进化的角度来看，我们

　　因为谷氨酸是天然食品中最常见的一种氨基酸。

　　芝加哥大学(University of Chicago)副约翰•普雷斯科特(John Prescott)认为，这是第五种

　　味觉和其他味觉一样有其作用。他认为，甜味暗示着食物中含有提供能量的碳水化合物，就像甜味暗示着食物中含有蛋白质一样。他说，苦味提醒我们食物中有毒素，酸味提醒我们食物变质，咸味暗示食物中有矿物质。

　　那么，关于第五种味道，我们还知道些什么呢?

　　师资点题剑桥雅思7听力：

　　考题精解

　　Question 31 B

　　当听到发言人说Today I am going to explore why it is so ...就要留意了，接着听到more importantly这一信号表达，确定答案就是后一句how does it enhance the flavour of food?中，而这一句含义等同于B选项，确定答案是B。

　　Question 32 C

　　1908是定位词，听到它后，接着听到the ingredient in Japan ... was actually discovered to be glutamate by scientists working there，discover与C选项中的identify是同义词，判定正确答案为C。

　　Question 33 A

　　1956是定位词，听到1956后，接着听到the speed of the process was improved，and industrial production increased dramatically, manufacture与produce同义，确定正确答案为A。

　　Question 34 water

　　当考生听到sodium之后，紧接着听到nine point six percent water, 9.6%是定位词，确定Question 34正确答案是water。

　　Question 35&36 meat, cheese

　　当发言人讲到protein-containing foods时，立即定位Question 35&36，接着听到so this includes food such as meat and cheese，确定答案是meat，cheese。

　　Question 37 5th / new taste

　　当听到In 1908，立即定位此题，接着听到Kikunae Ikeda identified a fifth taste。而identify与discover属于同义词，确定正确答案是5th/ new taste。

　　Question 38 common

　　演讲者提到It does make perfect evolutionary sense that we should have the ability to detect or taste glutamate ...确定Question 38的答案在后面。接着听到because it is the amino acid which is most common in natural foods. So与Most同义，in natural foods与naturally同义，Question 38需要填一个形容词，正确答案为common。

　　Question 39 bitterness

　　当考生听到carbohydrates后，紧接着听到bitterness, he says, alerts us of toxins in the food。确定正确答案是bitterness。

　　Question 40 minerals

　　当听到saltiness后立即定位于Question 40，紧接着听到signals the presence of minerals。确定正确答案是minerals。