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托福听力练习-科学美国人60秒:糖衣延长香蕉寿命

2017-04-02 16:24:00来源：科学美国人60秒

点击查看>>科学美国人60秒音频：糖衣延长香蕉寿命

　　科学美国人60秒听力练习：糖衣延长香蕉寿命

　　科学美国人60秒英文文本

　　One day the banana is perfect. Bright yellow, firm, flavorful. But even within the same day brown spots appear on your perfectly ripe banana, its flesh turns mushy, and it's destined for the compost or at best, banana bread.

　　But scientists are developing a way to extend the life of bananas. It's a spray-on coating made from chitosan—a substance found in crab and shrimp shells. The new gel can be sprayed on bananas to slow the ripening process by up to 12 days.

　　Like other fruit bananas remain alive after being picked and they actually continue to respire. This means they take in oxygen and release carbon dioxide. The more the banana breathes the faster it ripens and then rots. Bananas ripen more quickly than most fruit because they don't naturally slow the respiration after being picked, in fact it speeds up, giving bananas their notoriously short shelf life.

　　Chitosan not only kills the bacteria on banana's skin that then leads to rot, it also significantly slows down the respiration in the first place. So bananas won't drive you bananas.

　　中文翻译请点击下一页

本文关键字: 托福听力 科学美国人

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