时间:2018-12-28 作者:英语课 分类:初学者听力文摘精选


英语课

Some methods of preserving food are easy to understand. 



一些保存食物的方法很容易理解。



For example, it's easy to see that freezing your food, or packing it in salt, would make it inhospitable to the microbes which would otherwise cause it to spoil.



比如,把食物冷藏,或者用盐腌起来,都是很常见的方法。通过这些方法,不给细菌提供滋生的环境,以防止食物腐败变质。



You might wonder, however, about jams, jellies, and preserves, all of which are protected from spoiling by a high concentration of sugar.



不过,果酱,果冻和蜜饯都是用高浓度的糖来防止其变质的,你可能对此感到疑惑。



Sugar is one of the most basic foods for all life--bacteria and mold like to eat it just as much as we do. On today's Moment of Science we'll learn how too much of a good thing can be deadly, at least for microorganisms.



糖是生物的最基本食物之一-如我们一样,细菌和真菌也喜欢糖。在今天的《科学时刻》节目中,我们来见识见识,什么叫物极必反:太多的糖也会致命-至少对微生物来说是如此。



Sugar works not by poisoning the food-spoiling microbes, but by causing them to literally 1 die of thirst.



糖之所以能杀灭会令食物变质的细菌,并不是因为它有毒,而是高浓度的糖让细菌“渴死”了。



This is because sugar attracts water very well; the more sugar there is in any solution, the more water it tries to draw from its surroundings. This is bad news for any microbe that happens to be inside a jar of jam. High concentrations of sugar will suck the microbe's vital water right through its cell wall, causing it to dehydrate 2. This process is called "osmosis," and it can be deadly for bacteria and mold.



这是因为,糖的吸水性较好,在任何溶液中,糖的含量越高,其越能从周围吸水。这对恰巧滋生在一瓶果酱里的细菌来说可不是什么好消息。高浓度的糖会将细菌体内赖以生存的水分从细胞壁吸引出来,造成细菌脱水。这一过程被称为“渗透作用”。对细菌和霉菌来说,这可能是致命的。



In order for osmosis to work, the sugar concentration has to be quite high. If any water falls onto the surface of your jam, the sugar concentration at that spot might become low enough to allow mold to grow. That's why it's important to take the back up measure of refrigerating all jams, jellies, and preserves once you've opened them.



为了让渗透作用发生,糖的浓度必须达到很高。如果你的果酱上落了一滴水,那一点的糖的浓度可能就降低了,到了霉菌可以滋生的程度。这就是为何,果酱、果冻和蜜饯一旦开封,就一定要放到冰箱冷藏。



Like an oasis 3 in the desert, condensed water dripping from the jar's lid can give a dehydrating microbe the relief it needs.



如同沙漠中的绿洲一般,凝结的水滴从瓶盖上落下,便给正处脱水状态的细菌必要的喘息时机。



1 literally
adv.照字面意义,逐字地;确实
  • He translated the passage literally.他逐字逐句地翻译这段文字。
  • Sometimes she would not sit down till she was literally faint.有时候,她不走到真正要昏厥了,决不肯坐下来。
2 dehydrate
vt.使脱水
  • People can very quickly dehydrate in the desert.人在沙漠里很快就会脱水。
  • Without these structures, many warm-blooded animals would quickly dehydrate,especially in dry climates.没有这样的结构,许多温血动物将很快脱水,特别是在干燥的气候条件下。
3 oasis
n.(沙漠中的)绿洲,宜人的地方
  • They stopped for the night at an oasis.他们在沙漠中的绿洲停下来过夜。
  • The town was an oasis of prosperity in a desert of poverty.该镇是贫穷荒漠中的一块繁荣的“绿洲”。
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ADPase
Alexes
analysis of fatigue data
anticoagulant agent
arnouls
ass-breaths
best maid
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Bonna
bullock one's way
carnationed
catalogue sale
cellular type endosperm
chlorinated soda solution
coffee-bean sign
condomized
connectathon
continuous learning
Coxeter-Dynkin diagram
cross-structure bending moment
dermatitis skiagraphica
digital record
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don't-care couples
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entrism
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escalation of fault
ex-actly
exserticlava uniseptata
external-compensated
fish story
flat-leaf spring
floppy disks
frame sawing machine
Galapagos penguin
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gooderoon
Google Code
Grünendeich
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htnf-?
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International Association for Time-Keeping
International Labor Oraganization
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Mamori
meet ... halfway
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Production Information Control System
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protaetia fusca
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Sinlu
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Tringa flavipes
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Virgilite
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white colony
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work on all cylinders
youing