时间:2019-01-02 作者:英语课 分类:VOA2003(上)-社会广角


英语课

 



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 dryers 2. The easiest to build is called the direct dryer 1. 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 insulation 3, 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 Celsius 4. 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 nutrients 5 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
 



n.干衣机,干燥剂
  • 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。
n.干燥机( dryer的名词复数 );干燥器;干燥剂;干燥工
  • 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
n.隔离;绝缘;隔热
  • 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。
adj.摄氏温度计的,摄氏的
  • 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。
n.(食品或化学品)营养物,营养品( nutrient的名词复数 )
  • 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》
学英语单词
'Uiha I.
alopecia symptomatica
aquile
bakestones
battery box cover
caats
carbohydrate equivalent
cathodic synthesis
Ceptaz
charcoal of animal origin
chemical deposits
Cin
cloverleaf skull
colletotrichum cypripedii hori
common fractional size
common soybean varieties
configuration space instability
contralateral associated movement
control command program
control cubicle
Curza, Pta.di
dental sac
dick inches
Dionysius I
direction-finder set
district cross-cut
East Prospect
electromagnetic ammeter
end pipe connection
Epistle to the Hebrews
ethylene glycol diacetate
exemplums
Fiume
foot post
functional parts
genital corpuscles
geodesic parallels
give sb a rap on the knuckle
Haemachromatosis
Haematoconite
helotage
hexakisooctahedron
hrozny
jetten
joshing you
juice groove
keep...in subjection
kersten
kickback transformer
Lapin Lääni
lawful heir
light maintenance
link state advertisements
machine house
mandill
manufacturing procedure
march unit
menopausal period
mp4
multipaths
myringoscopy
northern parulas
number of common initial
ollendick
ovicell
Parmeliopsis
penetrating injury of kidney
pipe-support
plenye
power perch
protoyonogenin
quadratic residue
rebous
redundancy term
relationship of production
seesaw the point
SEPN
show interest in
skinflute
soil mineralogy
soup-strainers
sport cruiser
stereofunduscope
sudden load reduction
sumodom
sunshine time
tain
terminal aerodrome forecast
toroidal geometry
tower fermenter
Transjordanians
trip recorder
tweenen-brain
uncinula verniciferae p.henn.
under-frock
underdoses
User Profile Editor
varde
volumnia
weak data problem
wirecutter
zaranj