问题 问答题 简答题

简述淀粉的糊化过程。

答案

参考答案:

淀粉混于冷水中搅拌时成为乳状悬浮液,称为淀粉乳浆。若停止搅拌,经一定时间后,则淀粉粒全部下沉,上部为清水,这是因为淀粉不溶于冷水,且其相对密度较水大的缘故。淀粉颗粒不溶于冷水是由于羟基间直接形成氢键或通过水间接形成氢键的原因。氢键力很弱,但淀粉粒内的氢键足以阴止淀粉在冷水中落解。淀粉在冷水中有轻微的润涨(直径增加10%-15%),但这样润涨是可逆的,干燥后淀粉粒恢复原状

阅读理解

The first time Luca heard the Island of Inventions, he was very young, but the wonders he heard about sounded so unbelievable to him that they were forever kept in his memory. Since then, he never stopped searching clues which might lead him to that place of wonder. He read widely to collect information.

Taking a little from here and there, he got quite a clear idea of what the Island was really like. It was a secret place, where all the great men learn and invent together. To be able to join that select club, you had to have created great inventions. Only then could you receive the invitation.

To get a chance, Luca spend the years studying and inventing. Every new idea he got, he made it into an invention, and if there were anything he didn’t understand, he would seek help. Soon he met other brilliant inventors too, and he told them of the secrets of the Island. These young inventors would likewise dream of being sent “the letter”.

As time passed, the disappointment of not being sent the letter gave rise to even greater cooperation and help between them. Their inventions soon became known throughout the world.

But no invention came.

They didn’t lose heart. They continued learning and inventing, trying to come up with better ideas. Fresh talent was added to their group. One day, Luca, already very old, was speaking with a brilliant young man who had written to join their group. Luca told the young man the secrets of the Island, and of how he was sure that they would receive an invitation. Surprised, the young inventor said: “What? You mean this isn’t really the Island of Inventions?”

It inspired Luca and he realized that his dream had become true.

小题1:Luca read widely to ________.

A.get information about the great inventions

B.get clear ideas about the island for vacations

C.seek massages about the secret club of inventions

D.get more knowledge for the benefit of his inventions小题2:Luca and other brilliant inventors around him shared a dream of _______.

A.being great inventors of worldwide fame

B.being accepted as members of the Island of Inventions

C.being inventors envied by members of the Island of Inventions

D.being remembered for the contribution to scientific development小题3:What is the effect of their not being given “the letter”?

A.They were disappointed, while it encouraged them to work harder.

B.They became desperate and decided to have another way of living.

C.They changed their strategy and promote their inventions publicly.

D.They gave up their dream while continued their inventions together.

单项选择题