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  3. Why does cream go bad faster than butter? Some researchers think they have the answer, and it comes down to the structure of th

Why does cream go bad faster than butter? Some researchers think they have the answer, and it comes down to the structure of th

admin2009-06-15  58
问题 Why does cream go bad faster than butter? Some researchers think they have the answer,  and it comes down to the structure of the food, not its chemical composition--a finding that could help rid some processed foods of chemical preservatives.
Cream and butter contain pretty much the same substances, so why cream should sour much faster has been a mystery. Both are emulsions--tiny globules(小球体)of one liquid evenly distributed throughout another. The difference lies in what’s in the globules and what’s in the surrounding liquid, says Brocklehurst, who led the investigation.
In cream, fatty globules drift about in a sea of water. In butter, globules of a watery solution are locked away in a sea of fat. The bacteria which make the food go bad prefer to live in the watery regions of the mixture. "This means that in cream, the bacteria are free to grow throughout the mixture," he says.
When the situation is reversed, the bacteria are locked away in compartments(隔仓室)buried deep in the sea of fat. Trapped in this way, individual colonies cannot spread and rapidly run out nutrients(养料). They also slowly poison themselves with their waste products. "In butter, you get a self--limiting system which stops the bacteria growing," says Broeklehurst.
The researchers are already working with food companies keen to see if their products can be made resistant to bacterial attack through alterations to the food’s structure. Brocklehurst believes it will be possible to make the emulsions used in salad cream, for instance, more like that in butter. The key will be to do this while keeping the salad cream liquid and not turning in into a solid lump.
选项 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
答案A
解析 第二段指出研究的领导人是Brocklehurst，所以第一段给出的是他的研究结果。第一段说这一发现能有助于加工品中去除化学防腐剂。故A符合题意。B、C、D是研究中的发现，而非重大意义。
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