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第1段
1 .<-NARRATOR:-> Listen to part of a talk in a food science class.
听一段食物科学课堂上的片段。
第2段
1 .<-FEMALE PROFESSOR:-> Everyone knows food can become spoiled—go bad and become inedible.
谁都知道食物会腐败——腐烂并且不可食用。
2 .Usually, the cause is harmful bacteria that grow naturally in food.
通常，腐败是由食物中自然生长的有害细菌引起的。
第3段
1 .So, one of the best ways to prevent food from spoiling is to slow down bacterial growth.
所以，预防食物腐败的最好方式之一就是减缓细菌的生长。
2 .But how do you do that?
但是，如何实现呢？
3 .Well, what influences how fast bacteria grow?
那么，什么影响细菌的生长速度呢？
4 .Mainly, it’s temperature and moisture.
总体上，是温度和湿度。
第4段
1 .So if you want to prevent food spoilage, you need to slow bacterial growth by controlling these factors.
所以，如果想预防食物腐败，需要通过控制这些因素来减缓细菌生长。
2 .Why’s controlling temperature so important?
为什么控制温度这么重要呢？
3 .Because the bacteria that cause food spoilage grow fast at warm temperatures and more slowly at cooler temperatures.
因为能引起食物腐败的细菌在高温下生长快而在低温下生长慢。
第5段
1 .When your food is kept cool, it lasts longer, right?
当食物被冷藏，就能保存得更长，不是吗？
2 .For example, fresh fish left out in the sun on a warm day will spoil in a few hours.
例如，热天暴露于阳光下的鲜鱼几个小时就会腐败。
第6段
1 .But if you freeze the fish, it will keep for months and months, right?
但如果鱼被冷冻，就能保存好几个月，不是吗？
2 .That’s because low temperatures drastically slow down bacterial growth.
这是因为低温能大大地减缓细菌的生长。
第7段
1 .Now, I said that moisture’s another factor you need to control.
而且，我说过湿度是另一个需要控制的因素。
2 .And every living thing needs moisture, and bacteria are no exception.
所有生物需要湿度，细菌也不例外。
3 .Food that’s high in water content provides the moisture that bacteria need to grow.
含有大量水的食物为细菌的生长提供了湿度。
第8段
1 .Let’s, uh, let’s compare two different kinds of milk, okay?
我们来比较两种不同的牛奶，好吗？
2 .Let’s compare regular liquid milk with dried, powdered milk.
我们比较液体的牛奶和干燥的奶粉。
3 .Regular milk spoils quickly, right?
常规的牛奶腐败很快，是吧？
4 .But milk in powder form can be stored quite a long time…in fact, for years.
但奶粉就能储存很长时间...实际上，好几年。
5 .Of course, bacteria are present in powdered milk too.
当然，奶粉中也有细菌存在。
第9段
1 .But what’s different between powdered and regular milk is the water content.
但奶粉和常规牛奶的区别就在于水分含量。
2 .Powdered milk has had the water, the moisture removed, and without moisture bacteria can’t grow.
奶粉把水分除掉了，没有水分，细菌不能生长。
3 .And this isn’t true just for milk; just about any fresh food will spoil more quickly than a dried food.
但是，牛奶却不是这样；任何新鲜食物都比干燥食物腐败更快。