(单词翻译:单击)
You know that horrible, sour smell that comes from expired milk? Yeah.
过期牛奶可怕的酸味还有印象么?没错 。
You only need to smell it once to make sure it never happens again.
只要闻过一次保准这辈子都不想再来第二次 。
Luckily, many food manufacturers put some kind of Sell By, Best By,
幸运的是,很多食物生产商在他们的产品上都保质期、最佳食用期、
or Use By date on their products to tell you... well, actually, they don't tell you much.
或是此日期前食用等标识来告诉大家...好吧,事实上他们也没告诉你什么 。
These labels are mainly for quality and flavor purposes, not safety.
这些标签主要是保证质量和食物的味道,而非食物的安全 。
And a lot of common foods are edible past what it says on the label.
多数普通食物即使过期了也可食用 。
This can make it difficult to figure out what you can eat and what needs to go in the compost bin.
这就使得区别哪些食物可以吃、哪些食物需要扔进垃圾桶变得困难 。
But understanding what's happening chemically when foods go bad, both before and after those dates pass, can help you out.
但是理解保质期前后食物变质过程中发生的化学变化能够帮助到你 。
A product's real expiration date is tricky to predict,
产品的真实保质期很难预测,
because it can be affected by everything from the sanitation of the factory to the temperature of your fridge.
因为保质期会受到工厂环境、冰箱温度等的各种影响 。
But a lot of it depends on what kind of food you're buying.
但是多数还是取决于你购买的是什么食物 。
Produce, for instance, can become unsafe anywhere from hours to weeks after you buy it; a huge variation most labels don't account for.
例如,农产品,在你购买后的几小时几星期都可能变得不安全;这是大部分标签无法解释的巨大变量 。
Most of this has to do with when it gets moldy, and not about things like brown spots.
大部分问题是从发霉开始的,和褐色的斑点无关 。
Although those don't look pretty, they're harmless. Mold, meanwhile, can actually hurt you.
虽然那些斑点看起来并不漂亮,但是它们是无害的 。而霉菌对人类有害 。
Some strains produce substances called mycotoxins, which can cause everything from skin infections to internal bleeding and death.
一些菌株会产生一些被称为霉菌毒素的物质,会引起皮肤感染、内出血和死亡的问题 。
And because produce is such a water- and nutrient-rich home for mold,
由于农产品的水分和营养成为了霉菌的温床,
it can start growing as soon as 24 hours after you bring your produce home.
所以在你把农产品买回家的24小时,霉菌就开始生长 。
And it grows even faster in warm temperatures, like on your sunny kitchen countertop.
霉菌在温暖的环境中生长更加迅速,比如在沐浴阳光的厨房台面 。
Extending the shelf life of your produce is pretty easy, though: Just throw it in the fridge.
延长农产品的保质期很简单:只用把它们放进冰箱 。
Chemical reactions happen more slowly at cold temperatures, so it takes longer for mold to grow and reproduce in there.
在低温中,化学反应发生更加缓慢,所以在低温中,霉菌的生长和繁殖所需时间更长 。
But it will grow eventually.
但是最终还是会长的 。
And when it does, whether it's after a day or a few weeks, it's time for the compost bin.
当霉菌出现时,不论是一天还是几个星期,都是时候把它们扔进垃圾桶了 。
Dropping the temperature might be a great trick for a lot of food preservation,
降温或许是延长食物保质期的小技巧,
but if you want to really push back the expiration date, you have to kill bacteria before letting them reproduce.
但是如果你想真的将保质期向后推,你不得不在细菌繁殖前,将它们消灭 。
That's not easy with produce, but it's exactly how we treat milk.
对农产品来说很不不太容易,但是我们就是这样保存牛奶的 。
According to the label, milk is usually at its best for around two weeks after you buy it.
根据标签,通常牛奶的最佳使用日期是在你买回家后的两周左右 。
But depending on the kind you buy and how you treat it, it could really expire a few days later, or earlier.
但是这也取决于你买的是哪种牛奶以及你如何储存它,牛奶可能在几天后甚至更早就过期了 。
Traditional milk goes through the process of pasteurization, a heat treatment process that denatures enzymes in living bacteria and renders them harmless.
传统牛奶经过巴斯德氏杀菌法、热处理过程等过程改变活菌中酶的性质并将它们变成无害酶 。
And it does a good job, but it's not perfect.
这确实是个不错的方法,但是不是完美的方法
Some of those bacteria survive pasteurization, and over time, they convert the sugars in milk into lactic acid.
其中一些细菌在巴斯德氏杀菌中存活了下来,它们随时间将牛奶中的糖分转换成了乳酸 。
That's what gives spoiled milk that sour smell.
这使得变质奶牛发出酸味 。
Normally, this process takes a couple of weeks and, typically, it's still drinkable for around five days after the Sell-By date.
通常这个过程需要几周时间,在保质期五天左右仍可食用 。
But if the milk gets exposed to slightly warmer temperatures somewhere along the shipping route,
但是如果在运输过程中,牛奶被暴露在稍微温暖的温度下
or if you run your refrigerator a few degrees warmer, it can spoil faster.
或者你将冰箱的温度调高几度的话,牛奶就会迅速变质 。
And while you're probably not going to catch anything life threatening from drinking spoiled milk, you can catch some brutal food poisoning.
虽然喝变质的牛奶不会有什么生命问些,但是你可能会严重食物中毒 。
The good news is, it's easy to tell if milk's gone bad. Just give it a whiff, and take in that lovely lactic acid smell.
好消息是,分别牛奶是否变质还是很容易的 。小闻一下,吸入迷人的乳酸的味道 。
Finally, while heat treatments are awesome for getting rid of bacteria in milk, you'll need a different strategy for meat.
最后,虽然热处理能够起清除奶中的细菌,但是对付肉类,需要不同策略 。
Typically, the Best or Use By dates on these products is for a week or so past purchase.
这类产品的保质期是一周或买后就要马上食用 。
But while it's often safe past then, it doesn't last for that much longer.
但虽然过了保质期也是安全的,但是肉类的保质期没那么久 。
That's because meat is a prime breeding ground for bacteria.
这是因为肉类是细菌的最佳滋生地 。
It's a wet, nutrient-dense home with all kinds of fuel sources.
肉类是潮湿且营养密集的地方,还有各种燃料源 。
For a few days, these bacteria won't cause you any trouble because there aren't that many of them.
几天的时间,这些细菌不会对你造成任何问题,这是因为这时细菌还没有那么多 。
But over time, they'll multiply. And that's when you get problems.
但是随时间推移,它们会繁育 。并且这个时候就会对你造成问题 。
Bacteria, like Psuedomonas or Lactobacilli, feast on the meat's surface,
像假单胞菌或乳酸杆菌这样的细菌在肉的表面大吃大喝,
where there are free floating sugar molecules and light weight compounds to nom on.
在这里有免费的浮动糖分子和轻便的化合物 。
Some of these bacteria can make you sick, but they do at least announce their presence.
虽然一些细菌会让你生病,但是至少它们确实会宣示自己的存在 。
As they break those compounds down, they leave behind some nasty smelling byproducts.
当它们分解那些化合物时,它们会留下一些难闻的副产品 。
These have all kinds of shapes and compositions, but they all fall into a category called volatile organic compounds, or VOCs.
这些副产品有各种形状和组成,但是它们都被归为一类,被称为挥发性有机物或VOCs 。
Normally, these VOCS smell like rotten meat.
通常这些VOCs闻起来就像是腐烂的肉一样 。
And because you find them when bacteria have been chowing down and multiplying,
由于你在细菌已经大快朵颐并已经繁殖的时候才发现它们,
there's a pretty strong sign your meat has gone bad.
这就强烈预示着你的肉已经变质了 。
Besides the smell, you can also probably tell your meat has expired based on how it looks.
除了这些难闻的味道外,你还可以根据肉的外表来判断 。
For example, VOCs like hydrogen sulfide can convert the natural muscle pigment in meat into something that looks more green.
例如,VOCs,比如硫化氢可以肉中的天然肌色素转换成一些绿色的东西 。
Typically, all this happens a few days after the Use By date on that sticker.
这一变化发生在使用日期后的几天 。
But if you notice any of those funky smells or a little slime on your beef… it's time for it to go, no matter when it happens.
但是如果你注意到了牛肉上的任何恶臭或粘液...是时候扔掉它了,不论是什么时候变成这个样的 。
Food science can be tricky, and those ambiguous labels don't always help.
食品科学可以很微妙,并且那些模糊不清的标签并不总是有用 。
Knowing a little bit about how and why food expires can help you keep your fridge full for longer.
了解食物如何以及为何过期能够帮助你保持冰箱食物 。
But if you're really uncertain… it's okay to play it safe.
但是如果你真的不确定的话,就不要冒险啦 。
Thanks for watching this episode of SciShow!
感谢收看本期《科学秀》!
Scishow is a production of Complexly, which also produces channels like The Financial Diet where Chelsea, Erin,
《科学秀》由Complexly出品,Complexly的节目还有《The Financial Diet》,节目中Chelsea、Erin
and Lauren dive into personal finance topics with no fear.
以及Lauren带你深入私人金融话题 。
If you want to learn other ways to help keep your fridge fuller longer, and on a budget, check out their video on Rules for Mastering The Grocery Store.
如果你想知道怎样保持冰箱食物,请观看《掌控杂货店法则》 。
From the emotional side of money to technical financial terms, you'll learn tricks to improve your life by getting a better handle on money.
从金钱的情感方面到技术金融术语,你将学到如果通过更好的掌控金钱来改善生活 。
Check out new videos every Tuesday and Thursday on The Financial Diet.
《The Financial Diet》每周周二周四更新 。