评论
打印
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。
