英國學生科學讀本 Lesson 91 牛奶及用途(2)

Soon all the little balls of cream have their skins or coats broken, and then the tiny pieces of milk-fat inside them stick together and make a lump of yellow butter. You can make a little butter for yourself by putting a few spoonfuls of cream into a bottle, and shaking it as hard as you can for a while; but you will likely feel very tired before the butter appears.

很快, 奶油小球的外膜破碎, 里面的乳脂顆粒則會黏在一起成為一塊黃油。你也可以自己制作黃油：將幾勺奶油倒入瓶中, 然后竭盡全力地搖晃一陣瓶子;不過, 在黃油成型之前, 你一定會累得不行。

The "skim-milk" which remains after the cream has been taken away is of a bluish-white colour; and while new milk sells for, perhaps, threepence per quart, skim-milk fetches only a penny. Yet there is good nourishment in skim-milk.

不包含奶油的“脫脂牛奶”是一種青白色物質(zhì);如果鮮牛奶的價格是每夸脫三便士, 那么脫脂牛奶就只能賣到一便士。然而, 脫脂牛奶的營養(yǎng)價值同樣很高。

Let us add a little acid—vinegar will do—to some skim-milk. This makes it curdle , and we see little white jelly-like clots or "curds" forming. We will strain off the curds by squeezing the curdled milk through a piece of muslin. The white and solid curds that remain only need pressing to turn them into "cheese. "

現(xiàn)在, 我們往脫脂牛奶中加一些酸性物質(zhì), 比如醋。這樣的話, 牛奶就會凝固, 我們能夠看到逐漸形成的膠狀凝塊或者“凝乳”。我們用一塊棉布將凝固的牛奶包裹起來, 用力擠壓, 過濾掉凝塊。剩下這些白色的固體凝乳經(jīng)過壓制便可成為“奶酪”。

The watery liquid that runs through the muslin is called "whey. " Dissolved in the whey there is a little milk-sugar, the substance that makes new milk taste sweet, and also some lime.

通過棉布流出的水質(zhì)液體就是“乳清”。而溶解在乳清中的物質(zhì)就包括少量的乳糖以及石灰乳, 正是前者的存在才使得鮮牛奶有些甜味。

Now we know why new milk is such an excellent food. The milk-fat and the milk-sugar which it contains warm our bodies and help us to do our work, the curd helps to form our flesh, and the lime helps to form our bones. You can now see how good it is for us to drink milk, and why we add milk to many other kinds of food, such as tea, coffee, and cocoa.

現(xiàn)在我們就知道了, 鮮牛奶果然是一種營養(yǎng)豐富的食物。乳脂與乳糖能夠給人體帶來熱量并且提供我們開展各類活動所需的能量;凝乳有助于人體的肌肉生長, 而石灰乳則可以促進骨骼發(fā)育。如此一來, 你應該就可以明白飲用牛奶能夠帶來的好處以及我們要在茶、咖啡與可可中添加牛奶的原因了。

Have you ever seen condensed milk ? This kind of milk is made by boiling fresh milk for some time, so as to evaporate part of the water contained in it, and then adding some sugar. The sweet, thick liquid thus made is then put into tins, which are carefully closed and sealed, so as to keep out the air. If kept in those air-tight tins, condensed milk will remain good for years.

你見到過煉乳嗎? 它的做法就是：將鮮牛奶煮沸并保持其沸騰狀態(tài), 從而將牛奶中的一些水分蒸發(fā)出去, 然后加入糖。隨后, 人們把這種甜蜜、濃稠的液體放入罐子中, 小心地蓋好并密封起來, 這樣就能夠阻隔空氣。如果保存在密封性能較好的罐子中, 即便經(jīng)過了好幾年, 煉乳依舊能完美如初。

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