问题 问答题 简答题

为什么有时人造奶油会出现内部颜色变浅且有氧化异味?

答案

参考答案:

人造奶油的甘油三酯中的不饱和脂肪酸与氧气发生氧化反应,生成氢过氧化物,氢过氧化物进一步分解成多种挥发性化合物如醛、酮、烃、醇、酯和少量芳香及杂环化合物,导致人造奶油内部颜色变浅,且有氧化异味。因此,为了避免人造奶油的氧化,须采取相应措施。

①人造奶油油相配方中不用或尽量少用含多不饱和脂肪酸(尤其是亚麻酸)含量较多的油脂,这些油脂最容易引起人造奶油氧化变质。

②必须对原料油脂和配料进行品质检验,即原料油脂的过氧化物和甲氧基苯胺检测以及油脂、水和铜、铁、镍的含量检测,不使用不符合质量要求的原辅料。

③避免空气(尤其是氧气)进入人造奶油中,因而加工中应注意以下方面:首先加工时,水相、油相及水油相混合时,应避免剧烈搅拌,以减少人造奶油中包含的空气(氧气)量;其次人造奶油包装贮存时应充入氮气或二氧化碳代替空气,以避免氧化;再次任用不透明的包装材料进行包装,并将人造奶油在低温下避光保存。最后使用抗氧化剂,如BHT(0.005%~0.02%)、PG、BHA(0.005%~0.02%)、异抗坏血酸钠、GRIN、DOXTM系列抗氧化剂等。

完形填空
Mrs. Green, including her husband and three children, lived in a city,   41_was very near the countryside. She worked  42  a teacher and gave music lessons at a school. Of course she was fond of.  43__. Mrs. Green had a good voice and she  44 her classes exciting. But she had a   45 point. Some of her notes (音调) were so high that they sounded like a door which needed   46 . In order to improve her notes, she took   47  chance that she could find to practise.
As her house was not big, she couldn't practise  48__ in it. So she usually left home, walking and singing  49 the country road. She practised her high notes  50 walking. However, each time she heard a person or a car   51  along the road, she  52 singing. She did not want her high notes to be  53 , for she was shy.
One afternoon a fast open car came up to her so  54   and so fast that she didn't  55 it until the car was only a few meters. She was practising some of her  56 and most difficult notes at that time. As the car passed by, she saw a  57 expression come over the driver's face. He stopped suddenly to  58 all the tires (轮胎) carefully.
Mrs. Green felt it shy to tell the driver what the   59  he had heard really was. The driver found 60  wrong, got back into the car and drove off.
小题1:
A.thatB.whichC.whereD.there
小题2:
A.asB.likeC.withD.on
小题3:
A.booksB.picturesC.sportsD.music
小题4:
A.gotB.supportedC.madeD.forced
小题5:
A.weakB.strongC.goodD.special
小题6:
A.paintingB.lockingC.cleaningD.oiling
小题7:
A.some B.eachC.aD.other
小题8:
A.operatingB.listeningC.singingD.other
小题9:
A.acrossB.besideC.close toD.along
小题10:
A.as soon asB.whileC.afterD.before
小题11:
A.comingB.disappearingC.leavingD.driving
小题12:
A.keptB.went onC.stoppedD.began
小题13:
A.foundB.madeC.hearingD.heard
小题14:
A.quietlyB.quicklyC.carefullyD.slowly
小题15:
A.recognizeB.catchC.realizeD.provide
小题16:
A.biggestB.highestC.niceD.largest
小题17:
A.puzzledB.sadC.seriousD.happy
小题18:
A.watchB.examineC.controlD.notice
小题19:
A.factB.noteC.noiseD.music
小题20:
A.the tiresB.everythingC.somethingD.nothing
单项选择题 案例分析题