问题 问答题 简答题

分析食品中脂肪测定提取剂的种类及各自的特点。

答案

参考答案:

(1)、乙醚:溶解脂肪的能力强,应用最多。乙醚可饱和2%的水。含水乙醚在萃取脂肪的同时,会抽提出糖分的非脂成分。所以必须用无水乙醚作提取剂,被测样品也要事先烘干。易燃。

(2)、石油醚:石油醚的沸点比乙醚高,不太易燃,溶解脂肪能力比乙醚弱,吸收水分比乙醚少,允许样品含微量的水分。对于结合态的脂类,必须预先用酸或碱及乙醇破坏脂类与非脂类的结合,才能提取。(有时也采用乙醚+石油醚共用。但是乙醚、石油醚都只能提取样品中游离态的脂肪。)

(3)、氯仿-甲醇:一种有效的溶剂,对脂蛋白、磷脂提取效率较高。特别适用于水产品、家禽、蛋制品中脂肪的提取。

完形填空

第二卷(非选择题,满分35分)

第四部分:写作(共两节;满分35分)

第一节:对话填空(本节共10小题;每小题1分,满分1分)

请认真阅读下面对话,并根据各题所给首字母的提示,在答题卡上标有题号的横线上,写出一个英语单词的完整、正确的形式,使对话通顺。

D="Doctor," P=Patient

D: Hello, w  (76)  can I do for you?                                          76     

P: Well, I’ve been getting lots of headaches I  (77)  .                               77     

The problem is that I’m busy p  (78)  for the College Entrance Exam.             78     

D: I see. Are you sleeping well?                 

P: No, not really.

D: Well, don’t get u  (79)  . I will do you some tests.                                79      

P: How I hope you will help me recover from my i  (80)  !                      80     

D: Ok, nothing s  (81)  . Your problem is that you feel too stressed.                     81       

P: Stress! Really?  

D: How much time do you take to r  (82)  yourself as well as to study per day?    82        

P: None at all. I don’t have any spare time.

D: I think you’ll do better if you c   (83)  your study with some relaxation.     83     

P: That’ll be great! Thanks.

D: Not at all. And in the meanwhile, you’d better t  (84)  regular exercise        84       

and have a balanced d  (85)  every day.                                      85     

P: I’ll try. Thank you! See you.

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