【最新版】2014届高考英语一轮单元复习精品阅读理解提升文章精选一百篇 (62)

　　Unit 64 The Story of Corn Before 1492, when Columbus "discovered" America, no one living in Europe knew corn existed. Up to this time, corn grew only in the Americas. Scientists believed corn was originally cultivated by Indians in the highlands of Mexico thousands of years ago. American Indians were growing corn in many parts of North America log before the first arrival of European explorers and traders. Christopher Columbus and the explorers that followed him took corn back to Europe and introduced it to the world. Native American Indians taught European colonists to grow many varieties of the corn including yellow, re, blue, pink, and black kernels. As time went on, the new settles to America began to depend on corn as one of the most important farm crops. American farmers have always wanted to grow strong healthy corn plants that yield as much as possible. In the later 1800s scientists worked on the development of hybrid corn. This research led to better varieties of corn and higher yields. Did you know corn is used to help produce antibiotics, baby foods, condensed milk, some fruit juices and even peanut butter? From the corn syrup in your soda pop to thousands of products -- animal feed, human food, drugs, cosmetics, corn sweetener and cleansers, just to name a few. Beyond its food and consumer product uses, corn is replacing petroleum in many industrial applications, from plastic containers to clean-burning ethanol. Because corn products are a biodegradable and renewable natural resource, they are better for the environment than their petroleum counterparts. Corn and products made from corn improve the lives of Americans in thousands of little way. If corn and its products weren't available, many common products would be less useful, more expensive, even unavailable. Here are some examples of the little annoyances and bigger problems Americans would face without corn: No freezing pizza. Freezing pizza is a problem, because the moisture in the sauce can migrate into the crust, making it so soggy that it's unappealing to eat. Modified corn starch is used to provide a barrier that prevents water migration and keeps the crust crisp. On a low-fat diet? Say thank you for corn. Many low-fat foods depend on corn-derived food starches to provide qualities that used to come from fats. Examples include everything from low-fat salad dressing to baked goods and meat products. Frustrating wallpapering. If you've installed wallpaper, you know how important it is to have time to adjust each strip accurately. Repositioning is possible because the wallpaper paste is made with corn starch modified to slow down its adhesive action. Brown lettuce leaves. Many fruits and vegetables start to turn an unattractive brown once they're cut and exposed to air. Citric acid, recognized as a safe food ingredient, can prevent browning and much of the US supply of citric acid is made from corn sweeteners. No coloring for kids. Whether playing with chalk on the sidewalk or crayons in school, American kids rely on corn. Corn starch is used to help such products hold together better when in use.