Drying Food

 

Broadcast: Jan 21, 2003
By Gary Garriott

Drying food is a simple, low-cost way to keep food safe for eating. Drying removes water that small organisms use to break down food into other substances. Some of these substances may be poisonous to humans.

A device that uses the sun is a good way to dry food. There are several kinds of solar dryers². The easiest to build is called the direct dryer¹. The sun shines directly on the food being dried. The direct dryer is a box with holes in it so that air can enter and leave the box. It has a cover made of clear glass or plastic. When the sun shines into the box, heat is produced. The heat is trapped inside the box and cannot escape back through the cover. The heat dries the food.

The solar dryer works better if the sides of the box are black. This is because dark colors hold heat while light colors reflect it. One way to make the sides black is to use wood that has been blackened by fire.

If you use black paint instead, be sure the paint contains no lead. Lead is poisonous to people, especially children.

The box can be made of almost any material such as wood, concrete or sheet metal. The dryer should be two meters long, one meter wide and twenty-three to thirty centimeters1 deep. The sides and bottom should have additional material, called insulation³, to keep the heat from escaping.

The surface on which the food is placed should permit air to enter from below and pass through to the food. A surface made of wires with small square openings works very well. You should use wire with the largest openings or squares that do not allow the food to fall through. Air that comes in from below the wire surface will also carry away water evaporated2 from the food as it dries.

A direct dryer will dry most vegetables in two-and-one-half to four hours at temperatures from forty-three to sixty-three degrees Celsius⁴. Fruits take longer, from four to six hours at the same temperatures.

Solar food drying is fast, safe, and low-cost. It is also healthy because nutrients⁵ such as Vitamin C are kept in the food. Solar dried food also tastes and looks good.

You can get more information about solar food dryers from the group Volunteers in Technical Assistance. You can contact VITA through the Internet at its Web address: w-w-w dot v-i-t-a dot o-r-g. (www.vita.org)

1. centimeter [5sentImI:tEr(r)] n. 厘米
2. evaporate [I5vApEreIt] v. (使)蒸发, 消失
 

1 dryer   

n.干衣机，干燥剂

参考例句：

• He bought a dryer yesterday.他昨天买了一台干燥机。
• There is a washer and a dryer in the basement.地下室里有洗衣机和烘干机。

2 dryers   

n.干燥机( dryer的名词复数 )；干燥器；干燥剂；干燥工

参考例句：

• Men also have hair dryers and, if they suffer from baldness, they use a growth stimulator, buy hairpieces, or have hair transplanted from the hirsute part of the scalp to the bare areas. 男士也有他们的吹风机，而且如果他们秃顶的话，还会用毛发生长剂、买假发，或者把头发从密集的地方移植到谢顶的地方。 来自《简明英汉词典》
• The dryers can be automated. 干燥机可以自动化作业。 来自辞典例句

3 insulation   

n.隔离；绝缘；隔热

参考例句：

• Please examine the insulation of the electric wires in my house.请检查一下我屋子里电线的绝缘情况。
• It is always difficult to assure good insulation between the electric leads.要保证两个电触头之间有良好的绝缘总是很困难的。

4 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

5 nutrients   

n.（食品或化学品）营养物，营养品( nutrient的名词复数 )

参考例句：

• a lack of essential nutrients 基本营养的缺乏
• Nutrients are absorbed into the bloodstream. 营养素被吸收进血液。 来自《简明英汉词典》