Oil and Water

To understand the emulsifying process, we must first accept the scientific

principle that oil and water do not naturally mix. Quite literally, they

find each other's presence repulsive. A good illustration of  this aversion

 is homemade  oil       and    vinegar salad dressing.When you shake or beat your

salad dressing, you do more than disperse the oil throughout the vinegar:

you also break down the oil into droplets minute enough to remain

temporarily suspended in the vinegar (which from now on we will call water,

because that tart condiment is in effect mainly water). The second you 

stop  agitating  the  dressing,  the  oil  droplets  start  to  combine 

into  units  too  large  to  be suspended in the water, and thus slither

their way upward, separating from the water in the process. The oil rises

to the top and the water sinks because oil has a lower specific density

than water. If you want a stable emulsion, you need an emulsifying agent

which prevents the oil droplets from combining  into  larger  units. 

Emulsifying  agents  occur  naturally  in  many  animal  substances

including egg yolks and milk. An emulsifying agent helps to keep the oil

particles from combining in three basic ways. First, the agent coats the

oil, serving as a physical barrier between the droplets. Second, it reduces

the water's surface tension, which, in turn, reduces the water's ability to

repulse oil. Third, the agent gives the surfaces of the oil droplets

identical electrical charges; since like charges repel each other the

droplets repel each other.

油和水

為理解乳化過程的發(fā)生，我們必須首先認識到這樣一條科學原理：水和油不能自 然混合，它們實實在在互相排斥。 家制的油醋沙拉調(diào)料就是一個好例子。

當你攪拌沙拉調(diào) 料時，你不僅使油擴散到醋里，而且使油滴被攪得很小可以懸浮在醋中(自此我們改稱它為 水，因為事實上這種酸性調(diào)味品的主要成份就是水)。

一旦你停止了攪動，油滴就會凝聚， 大到再也不能懸浮在水中時，它們就向上滑動出來而與水分離了。  因為油的密度小，所以 油會浮在水上。

如果想得到穩(wěn)定的乳化，就需要一種乳化劑。 它可以不讓油形成大的油滴。 自然界中，很多動物體中含有乳化劑，如蛋黃和牛奶。

乳化劑可以從以下三方面阻止油滴 凝聚。  一、  乳化劑包裹住油滴，在油滴間形成一道物質(zhì)屏障。  二、  乳化劑降低水的表面

張力，從而降低了水排斥油的能力。  三、  乳化劑使油滴表面帶上了同種電荷，因為同種電 荷互相排斥，油滴之間也相互排斥。

譯路通武漢翻譯公司整理

2012.7.12