问题 问答题 简答题

简述食品中αW与脂质氧化反应的关系。

答案

参考答案:

食品水分对脂质氧化既有促进作用,又有抑制作用。当食品中水分处在单分子层水(αW=0.35左右)时,可抑制氧化作用,其原因可能在于:

⑴覆盖了可氧化的部位,阻止它与氧的接触;

⑵与金属离子的水合作用,消除了由金属离子引发的氧化作用;

⑶与氢过氧化合物的氢键结合,抑制了由此引发的氧化作用;

⑷促进了游离基间相互结合,由此抑制了游离基在脂质氧化中链式反应。

当食品中αW>0.35时,水分对脂质氧化起促进作用,其原因可能在于:

⑴水分的溶剂化作用,使反应物和产物便于移动,有利于氧化作用的进行;

⑵水分对生物大分子的溶胀作用,暴露出新的氧化部位,有利于氧化的进行。

单项选择题 A1型题
阅读理解

阅读理解。

     I know what you're thinking: pizza (比萨饼)? For breakfast? But the truth is that you can have last

night's leftovers in the a.m. if you want to.

     I know lots of women who skip breakfast (不吃早餐), and they have a ton of different excuses for

doing it. Some say they don't have time. others think they're "saving" calories (卡路里), still others just

don't like breakfast food.

     But the bottom line is that eating in the morning is very important when you're trying to lose weight.

"Eating just about anything from 300 to 400 calories would be better than nothing at all," says Katherine

Brooking, R.D, who developed the super-easy eating plan for this year's "SELF CHALLENGE". And even

pizza can be healthy if it's loaded with vegetables, and you stick to one small piece.

     Breakfast is one meal I never miss, and the same goes for most weight loss success stories. Research

shows that eating breakfast keeps you from overeating later in the day. Researchers at the University of

Southern California found that breakfast skippers have a bigger chance of gaining weight than those who

regularly have a morning meal.

     So eat something in the morning, anything. I know plenty of friends who end up having no breakfast

altogether, and have just coffee or orange juice. I say, try heating up last night's leftovers-it may sound

crazy, but if it works for you, do it! I find if I tell myself, "You can always eat it tomorrow," I put away

the leftovers instead of eating more that night. Try it…you may save yourself some pre-bedtime calories.

And watch your body gain the fat-burning effects.

1. The word "leftovers" in Paragraph 1 probably means ____.

A. food remaining after a meal

B. things left undone

C. meals made of vegetables

D. pizza topped with fruit

2. What can we infer from the text?

A. Working women usually have breakfast in a hurry.

B. Many people have wrong ideas about breakfast.

C. There are some easy ways of cooking a meal.

D. Eating vegetables helps save energy.

3. According to the last paragraph, it is important to ____.

A. eat something for breakfast

B. be careful about what you eat

C. heat up food before eating it

D. eat calorie-controlled food

4. The text is written mainly for those ____.

A. who go to work early

B. who want to lose weight

C. who stay up late

D. who eat before sleep