英語(yǔ)時(shí)差：當(dāng)好香蕉變壞

on this Moment of Science Yael and Don discuss what causes the brown spots on bananas. Y: So Don, yesterday I was walking down the produce aisle when I saw it--long, ripe,yellow. The perfect banana. It really looked delicious and I had to have it. I took it home and hung it on a banana hanger. The very next morning, it developed nasty brown spots.

D: And you're wondering what gives.

Y: Right. It was a good banana yesterday. What happened?

D: It's no mystery, Yael. Those spots are a natural part of the ripening process. You see, just like all fresh produce, your bananas are alive. They're taking in oxygen to help them convert sugars into energy, and releasing carbon dioxide. This process is called respiration.

Y: I don't know, Don, this banana looks dead to me.

D: Now, the quicker a fruit or vegetable respires, the quicker it ripens. For most fruits,the respiration rate slows down after the initial growth stage and the fruit ripens slowly. The growth and ripening process of bananas, however, is different. Although at first the banana's respiration slows down too, when it's ready to ripen, the banana's pulp releases a chemical that increases respiration. This converts the starches in the banana to sugars and gives it its fabulous taste. And you know how good bananas taste!

Y: Watch it--you're drooling. But what does all this ripening have to do with spots?

D: Well, with all this respiration, the banana eventually processes all the starches available. And that's when it begins to die. Those brown spots are rot and decay.

Y: Poor thing. It just ran out of fuel.

D: Yeah, it's never easy seeing a good banana go bad.