Tingroom Radio—蜂蜜为什么变硬？（在线收听）

 Why Honey Turns Hard If a little honey drizzled on a piece of homemade toast or into a cup of tea is how you like to start the day, you’re not alone. One drawback to honey, though, is that after sitting too long on the shelf, it crystallizes and that soft, amber liquid turns to a hard, gooey mass. Actually, though, only part of the honey is crystallizing. Honey is made mostly of two kinds of sugar: glucose and fructose. What crystallizes is the glucose, so the more glucose there is in comparison to fructose, the more likely it is to crystallize. But before honey can crystallize, it needs what’s called a “seed” for the crystals to grow on. The seed might be a grain of pollen, a speck of dust, or even a scratch on the inside of the jar. But the best seed of all is a bit of honey that has already crystallized. Most of the honey in a supermarket has been heated and filtered to remove virtually all the possible seeds. That slows the crystallization, but the heating process also drives off some of the honey’s distinctive flavor. When honey does crystallize, you can soften it again in a microwave or a pan of warm water, but as it cools the crystallization will begin again–faster even than before. Honey crystallizes faster the second time because heat alone can’t remove all the seeds. Dust, crumbs, and other tiny particles that have accumulated since you first opened the jar will remain as seeds to start the process all over again.