各位咖啡控一定都注意到，平常當你向咖啡粉倒水的時候，會有氣泡冒出來，隨後粉末整體會膨脹，並且冒泡的形式和粉末的膨脹程度常常是不盡一樣。

　　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.

　　那麼這些氣泡到底是怎麼來的呢?實際上，這些氣泡中的氣體，是烘焙咖啡豆時產生的二氧化碳。形成氣泡外膜的是蛋白質或多糖類(與意大利濃咖啡表面覆蓋的氣泡成分相同)。

　　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).

　　往咖啡粉裏倒水時產生的氣泡，有的很細小，有的很大，有時幾乎不產生氣泡。這是因爲豆子釋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.

　　有人認爲，在沖泡過程中產生的氣泡是咖啡發澀的原因，然而這種說法並不完全準確。因爲即使是將氣泡撇出來，放到沖泡好的咖啡中攪拌，也喝不出和之前的味道有什麼不一樣。

　　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.

　　剛剛烘焙好的咖啡豆中含有大量的二氧化碳，如果立即磨成粉，倒入熱水時就會產生大量的氣泡。這些氣泡會妨礙咖啡的萃取，不過這也並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.

　　在這種情況下我們會發現，此時即便用平時的方法沖泡咖啡，味道也比正常的要淡。所以人們常常說：“新磨好的咖啡豆，要放一個晚上再用。”

　　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.

　　如果你泡咖啡時幾乎沒見到什麼氣泡，或者咖啡粉的膨脹度低，這是因爲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.

　　有人會說，如果咖啡粉不怎麼膨脹，那是因爲咖啡不夠新鮮。的確，烘焙後隨着時間的流逝，咖啡豆中的二氧化碳含量會越來越少。

　　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.

　　還有別的情況，是因爲咖啡裝包時放入了吸收二氧化碳的脫氧劑，或是由於使用了顆粒大的咖啡粉並緩慢倒入熱水，以及水溫較低等原因，都會導致咖啡粉膨脹度變低。

　　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.