Everyone knows food can become spoiled, go bad and become inedible. Usually the cause is harmful bacteria that grow naturally in food. So one of the best ways to prevent food from spoiling is to slow down bacteria growth. But how do you do that? Well, what influences how fast bacteria grow? Mainly it's temperature and moisture. So if you want to prevent food spoilage, you need to slow bacteria growth by controlling these factors. Why is controlling temperatureso important? Because the bacteria that cause food spoilage grow fast at warm temperatures, and more slowly at cooler temperatures. When your food is kept cool, it lasts longer right? For example, fresh fish left out in the sun on a warm day will spoil in a few hours, but if you freeze the fish, it will keep for months and months, right? That’s because low temperatures drastically slow down bacteria growth. Now I said that moisture is another factor you need to control, and every living thing needs moisture, and bacteria are no exception. Food that’s high in water content provides the moisture that bacteria need to grow. Let’s …uh let’s compare two different kinds of milk, ok? Let’s compare regular liquid milk with dry powdered milk. Regular milk spoils quickly right? But milk in powder form can be stored quite a long time, in fact, for years. Of course, bacteria are present in powdered milk too, but what’s different between powdered and regular milk is the water content. Powdered milk has had the water, the moisture removed. And without moisture, bacteria can’t grow. And this isn’t truth just for milk, just about any fresh food will spoil more quickly than the dried food.
Using points and the examples from the talk, explain two ways of preventing food spoilage and why they are effective.
Food spoilage is caused by bacteria and the two key factors to prevent food from going bad is temperature and moisture.
First, controlling the temperature can slow down the growth of bacteria, so food can be stored for longer time in cooler environment. For example, the fresh fish can be kept for months if being frozen, but they will go bad very quickly under the sun in warm days. Because the low temperature drastically slows down the growth of bacteria.
Plus, moisture is another factor to control. Food high in water content will go bad more quickly, because the moisture offers the bacteria necessary supplies to grow. For example, the liquid milk spoils quickly than the powdered milk. Because the water has been removed from the powdered milk, and without moisture, bacteria can’t grow.
vt. 欣赏；感激；领会；鉴别 （appreciate的第三人称单数）
They don't have any confidence that houses will appreciate in value.(TPO49-20)