各位咖啡控一定都注意到，平常当你向咖啡粉倒水的时候，会有气泡冒出来，随后粉末整体会膨胀，并且冒泡的形式和粉末的膨胀程度常常是不尽一样。

　　All you coffee fevers must’ve noticed, whenever you pour over the water into some coffee grounds, it bubbles up, swells and expands, with a “bloom” followed. The way it bubbles and expands are usually various.

　　那么这些气泡到底是怎么来的呢?实际上，这些气泡中的气体，是烘焙咖啡豆时产生的二氧化碳。形成气泡外膜的是蛋白质或多糖类(与意大利浓咖啡表面覆盖的气泡成分相同)。

　　So where exactly do those bubbles come from? In fact, the reason it happens is because of carbon dioxide gas is brought into the beans while roasting. The skin of those bubbles is made of protein and saccharides (Same as Expresso’s).

　　往咖啡粉里倒水时产生的气泡，有的很细小，有的很大，有时几乎不产生气泡。这是因为豆子释放二氧化碳的方式有所不同。

　　When you pour over the water, you would see some small bubbles, sometimes big ones, or other times, you don’t even see bubbles. That’s because the ways some beans leaching out CO2 are different.

　　有人认为，在冲泡过程中产生的气泡是咖啡发涩的原因，然而这种说法并不完全准确。因为即使是将气泡撇出来，放到冲泡好的咖啡中搅拌，也喝不出和之前的味道有什么不一样。

　　Some people think the bubble is the cause of coffee becoming rough, this is not completely true though. Because if you put some of those bubbles to a ready-to-drink coffee and stir it, you won’t find any different taste.

　　刚刚烘焙好的咖啡豆中含有大量的二氧化碳，如果立即磨成粉，倒入热水时就会产生大量的气泡。这些气泡会妨碍咖啡的萃取，不过这也并不代表咖啡豆就一定不好。

　　Beans are just roasted contain large amount of CO2. If you grind it right away, numerous bubbles will come up. These bubbles will affect the brewing process, though it doesn’t necessarily mean the beans are not good.

　　在这种情况下我们会发现，此时即便用平时的方法冲泡咖啡，味道也比正常的要淡。所以人们常常说：“新磨好的咖啡豆，要放一个晚上再用。”

　　If this is the case, you will find the taste lighter than usual, even if you brewed with the same method as you always did. That's why some people always say, leave your fresh grounds for an overnight before using it.

　　如果你泡咖啡时几乎没见到什么气泡，或者咖啡粉的膨胀度低，这是因为咖啡粉中的二氧化碳含量低。

　　If you don’t see many bubbles or the grounds don’t quite expand while brewing, it means there isn’t much CO2 contained.

　　有人会说，如果咖啡粉不怎么膨胀，那是因为咖啡不够新鲜。的确，烘焙后随着时间的流逝，咖啡豆中的二氧化碳含量会越来越少。

　　Some says if the grounds don’t quite expand, the coffee is not fresh enough. That’s correct. As time passes after the roast, there will be less and less CO2 contained in the beans.

　　还有别的情况，是因为咖啡装包时放入了吸收二氧化碳的脱氧剂，或是由于使用了颗粒大的咖啡粉并缓慢倒入热水，以及水温较低等原因，都会导致咖啡粉膨胀度变低。

　　Although there are also other cases that the grounds won’t expand so much. For instance, your coffee package is put in desoxidant that will absorb CO2, or your grind particles are too big and you pour over slowly, or the water is not hot enough.