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Why does my bottled water have an expiration date? Does this stuff actually go bad?
Hi everyone, Julian here for DNews. Have you ever left a glass of water out overnight.
And the next day, taking a drink, and noticed it tasted funny?
Does that mean the water is going bad, or what's happening here?
Well the water itself doesn't have any sugars or proteins like food, so microbes aren't consuming it and rotting it.
However, that's not to say the chemistry of the water hasn't changed.
By being exposed to air, the water absorbs some CO2, and a tiny portion of that, about 0.13%, is converted into carbonic acid.
Some carbonic acid will then lose a proton or two, forming bicarbonate or carbonate respectively.
This lowers the pH of water, making it slightly acidic and changing the taste.
So does that mean it's unsafe? Probably not, no. Unless you are a shellfish.
Carbonic acid forms about 4 million times more bicarbonate than carbonate, and shellfish need carbonate to build their shells.
The bias towards bicarbonate production means they have less to build their shells from.
Not only that, but the higher acidity can actually dissolve shells.
Since the Industrial Revolution, the ocean surface has become slightly more acidic.
So if you love oysters, there's another reason to care about CO2 in the atmosphere.
Anyway, if you're a human, the small shift in pH isn't going to be what hurts you.
The problem is water in an unsealed container has been exposed to bacteria.
Most tap and bottled water has chlorine additives, which will keep the microbes from multiplying for a day or two,
but after that they can go crazy. Water left outside can also start growing algae
and host mosquito larvae, which will make you sick and is gross to think about,
but not as gross as thinking about the dust inside your house landing in your water!
It can be purified with chemicals, like iodine or chlorine, or it can be filtered and boiled, and it'll be good as new.
Again, it's not the H2O breaking down and going bad,
it's just hosting other nastiness that spoils the taste.
Our ancestors didn't have the benefit of germ theory or chemical purification,
so when their water became unsanitary, they had to come up with a different solution.
When they set out for long voyages, Europeans sailors had stores of water in wooden barrels.
After a few weeks though, it would start to grow algae, so to get around this, sailors also brought along beer.
And when that beer ran out, they switched to that old pirate favorite, rum.
The alcohol in the beer and rum killed off bacteria, but the side effect was drunken sailors early in the morning.
In fact, British sailors actually got a daily rum ration until 1970.
Now though we can store water indefinitely without having to worry about its safety, provided it's stored correctly.
The CDC says commercially bottled water is the safest, but it should still be stored out of direct sunlight.
Some plastics release a hormone disruptor called bisphenol-A, or BPA, into the water when heated.
Plastic bottles are also permeable, so water should not be stored near pesticides or gasoline.
Aside from that though, you don't have to worry about the expiration date on bottled water.
That's a holdover from old New Jersey law that has since been repealed because there's no scientific evidence to support it.
Gotta love it when science informs lawmaking.
So now the question is, how much water do you actually need to drink? Trace covers that here.
A lot of our fluid intake comes from food. The rules say that we need to drink fluid,
so if we eat a banana or an orange, we consume their fluid, which is to say, we take their water.
Have you gotten sick from drinking water? Did you switch to rum? Or do you have any other questions you want us to field?
Let us know in the comments or on facebook or twitter.
Subscribe for more, and I'll see you next time on DNews.
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【冷知識】我都不知道水也會過期? (Does Water Ever Expire?)

102681 分類 收藏
Jeng-Lan Lee 發佈於 2017 年 8 月 10 日   黃世閔 翻譯   James 審核

影片簡介

水會過期嗎?這個問題應該大部分的人都沒有想過吧!但是為什麼水放久有奇怪的味道呢?這部影片幫大家詳細的解惑。

1
bottled water0:02
bottled water 是「瓶裝水」的意思,就是一般裝在寶特瓶的水,寶特瓶的英文是 plastic bottle,也就是「塑膠瓶」的意思。

我們生活中的水有分很多種,我們分別來看看:

tap water「自來水」:tap 是「水龍頭」,酒吧常見的盛裝啤酒的機器就叫做 beer tap。
distilled water「蒸餾水」:水煮沸蒸發後冷卻形成的水。
mineral water「礦泉水」:水中含有少量礦物質(如:鈉、鈣)的水。
sparkling water「氣泡水」:含有二氧化碳的水,像是汽水的口感。
water fountain/drinking fountain「飲水機」:室外常見直接對嘴的飲水機。
water dispenser「飲水機」:雖然與上方的也是飲水機,但這種是常見的盛裝式飲水機。

* 同場加映
天氣熱好渴?可是你真的能喝那麼多水嗎?Can You Drink Too Much Water?


2
proteins0:20
proteins 指的是「蛋白質」,是五大營養素的其中一類。人體中大概有16% - 20%是蛋白質組成,是構成細胞的基礎,負責人體的生理功能,如:DNA 複製、指甲和頭髮的生長、控制賀爾蒙等等。

一般來說,動物性蛋白質的蛋白質比植物性蛋白質的含量高,肉類、魚類、雞蛋、等都含有豐富的動物性蛋白質,花椰菜、菠菜、杏仁、南瓜子等有植物性蛋白質。
Your protein intake is crucial when it comes to building muscles.
蛋白質的攝取對於長肌肉相當重要。


以下來介紹五大營養素:

carbohydrate「醣類」
也就是碳水化合物,carbohydrate 的 carbon 是化學元素的「碳」,hydrate 是水合物,意思是含水的化合物,像是葡萄糖、果糖、澱粉都是碳水化合物。

proteins「蛋白質」
蛋白質分成兩類,有 animal protein「動物性蛋白質」跟 plant protein「植物性蛋白質」。

fat「脂肪」
脂肪的來源可以分成 animal fats「動物性脂肪」跟 plant fat「植物性脂肪」,動物性脂肪有豬油、牛油、雞油、魚油等,植物性脂肪有棕梠油、葵花油、橄欖油等。

minerals「礦物質」
礦物質又稱無機鹽,常見的礦物質有 calcium「鈣」、sodium「鈉」、magnesium「鎂」等等。

viatamin「維生素」
維生素又稱作維他命,它們是生物體所需要的微量營養成分,而一般又無法由生物體自己生產,需要通過飲食獲得。

3
chlorine1:18
chlorine「氯」是常見的化學元素之一,氯的化合物可以用來消毒,一般來說,我們許多使用的水都是有經過氯消毒過,去游泳池會聞到漂白水味,這也是因為游泳池有經過氯的消毒,而漂白水其中之一的成分就是氯。
Many people think it is the chlorine in the swimming pool that turns blonde hair green, but in fact, copper is the main reason.
很多人以為是游泳池裡的氯讓金髮變綠,但事實上,銅才是主要原因。


* 同場加映
比爾蓋茲化便便水為神奇?主持人喝給你看!Bill Gates and Jimmy Drink Poop Water


4
drunken sailor early in the morning2:08
drunken sailor early in the morning 這句是指白天醉醺醺的水手,這是出自一首歌 Drunken Sailor 其中一句歌詞,這是一首 sea shanty「船夫號子」,也就是水手在帆船做事時會唱的歌曲。

不過,注意影片中 earlyy 發音不是發 [ɪ],而是發 [aɪ],因為在某些版本的 Drunken Sailor 這首歌裡,early 這個字發音是 [ˋɝlaɪ],所以這句話就引用歌詞,也發音成 [ˋɝlaɪ],不過確實也有一些版本是唱 [ˋɝlɪ]

5
pesticide2:33
pesticide「殺蟲劑」,我們可以來看看這個字的組成,pesticide 是由 pest-cide 組成,pest 是「害蟲」的意思,而 -cide 的字尾有「殺掉、去除」的意思。
Pesticides can be harmful to the environment, and even people's health.
殺蟲劑對環境有害,甚至對人的健康也有害。


再來看看幾個常見字首的搭配吧:

herbicide「除草劑」:herb + -cide「藥草/花草」+「去除」
insecticide「除蟲劑」:insect + -cide「昆蟲」+「去除」
suicide「自殺」:sui + -cide「自己」+「殺」
homicide「他殺」:homi + -cide「人」+「殺」

看完影片後,小編也學了一課呢!所以只要好好的存放水,水是不會過期的喔,請大家不用擔心!

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