2017年12月英语四级阅读写作目的题讲解（2）

2017-09-04 15:04:06来源：新东方在线

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　　Passage 2

　　Why does cream go bad faster than butter? Someresearchers think they have the answer，and itcomes down to the structure of the food, not itschemical composition一a finding that could help ridsome processed foods of chemical preservatives.

　　Cream and butter contain pretty much the same substances, so why cream should sour muchfaster has been a mystery. Both are emulsions一tiny globules (小球)of one liquid evenlydistributed throughout another. The difference lies in what’s in the globules and what’s in thesurrounding liquid, says Brocklehurst, who led the investigation.

　　In cream, fatty globules drift about in a sea of water. In butter，globules of a watery solutionare locked away in a sea of fat. The bacteria which make the food go bad prefer to live in thewatery regions of the mixture. “This means that in cream, the bacteria are free to growthroughout the mixture, he says.

　　When the situation is reversed，the bacteria are locked away in compartments (密封仓)buried deep in the sea of fat. Trapped in this way, individual colonies cannot spread andrapidly run out of nutrients. They also slowly poison themselves with their waste products. Inbutter，you get a self-limiting system which stops the bacteria growing，” says Brocklehurst.

　　The researchers are already working with food companies keen to see if their products can bemade resistant to bacterial attack through alterations to the food's structure. Brocklehurstbelieves it will be possible to make the emulsions use in salad cream，for instance, more likethat in butter. The key will be to do this while keeping the salad cream liquid and not turning itinto a solid lump..

　　The significance of Brocklehurst research is that_____.

　　A. it suggested a way to keep some foods fresh without preservatives

　　B. it discovered tiny globules in both cream and butter

　　C. it revealed the secret of how bacteria multiply in cream and butter

　　D. it found that cream and butter share the same chemical composition

　　A 依据是文章第三行开头：a finding that could help ridsome processed food of chemical pre-servatives.

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