时差N小时 如何保存肉类?(上)（在线收听）

On the way home from the grocery, you get delayed so much that the frozen meat you’ve bought thaws out. The question for this Moment of Science is should you refreeze it? We’ve been told by reliable authorities that it’s not good to refreeze uncooked meat. Why not? If freezing the meat in the first place helps preserve it, why doesn’t this work the second time around? The answer to this question lies in the fact that all food has some bacteria in it, but normally not enough to hurt us. We freeze uncooked meat so that bacteria will not grow in it. But freezing does not kill all the bacteria that are already there, it just puts them in a kind of suspended animation. When the meat is thawed the bacteria come back to life and begin reproducing.

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从商店回家的路上，你的行程延误了，因为你刚买的冷冻肉开始融化。这今天的《科学时刻》的问题是我们是否应该再次冷冻肉？权威人士已经告我们再次冷冻肉，这种做法并不好。为什么呢？如果第一次冷冻肉能保存肉，为什么第二次冷冻就不行呢？问题的答案在于所有食物中都有细菌，但是细菌的数量还不至于伤害我们。我们将未煮过的肉冷冻，那样里面的细菌都不会生长。但是冷冻并不会杀死里面所有的细菌，只是抑制细菌暂停生长。当冻肉开始融化时，细菌又复活了，重新开始繁殖。