手沖咖啡為何會有泡泡？ Why does pour-over coffee have bubbles?
最近有人問，為何咖啡沖下去會有泡泡冒出來？到底是怎麼一回事？熱水加入咖啡粉後，就有泡泡出現？其實泡泡是咖啡新鮮度的表現喔。
Recently someone asked, why does the coffee have bubbles? What is going on? When hot water is pouring to ground coffee, why bubbles appear? In fact, the bubbles is a sign of the freshness of the coffee.
咖啡需要經過烘焙，而烘焙過程中，生豆中的水份蒸發、帶有大量木質纖維的豆體會膨脹，內部結構呈不規則蜂巢狀，蜂巢空間內會附著咖啡油脂及經烘焙而產生的氣體。在烘焙完成後，這些附著在內的氣體，會隨著時間慢慢消散；特別在磨豆後、著入熱水時，氣體會大量排出，這就是為何手沖咖啡時會有泡泡的原因了。
Coffee needs to be roasted. During the roasting process, the water in the green beans evaporates, the beans with a lot of wood fibers expand, and the internal structure is irregular honeycomb-like, coffee lipids or oil and gas will adhere to the honeycomb structure. After the roasting is completed, the gas attached to it will slowly dissipate over time; especially after the beans are ground and hot water pours in, the gas will be released in large quantities, which is why there are bubbles during pour-over brewing.
氣體是隨著時間而排出，所以愈新鮮的咖啡、會有愈多的氣體，而且容易出現比較大顆的泡泡；所以我們也可依泡泡多寡、來看豆子的新鮮程度。但同時，焙度愈深、累積的泡泡也愈多、愈大顆，所以淺焙豆子，雖然新鮮，會有比較少的氣體、也是正常的。
The gas is released over time, so the fresher the coffee, the more gas there will be, and larger bubbles are likely to appear. So, we can also find out the freshness of the beans according to the amount of bubbles. But at the same time, the darker the roasting degree, the more bubbles and bigger the bubbles will accumulate, so it is normal for lightly roasted beans, although fresh, to have less gas.
不過，我們之前也有討論過，這些氣體是不利於熱水萃取咖啡中的可溶性物質，所以才會有養豆的需求，養豆是等待這些氣體排出多一點、也同時讓藏在咖啡內的香氣、再多進到咖啡油脂中、讓萃取時、香氣更飽滿豐富。
However, as we have discussed before, these gases are not good for hot water extraction of soluble substances in coffee, so we need to have a coffee bean aging process. Bean aging process is to wait for more of gases to be released, and at the same time to let the aroma in coffee goes into the coffee lipids, so the aroma is fuller and richer during brewing.
這些看似平常的泡泡，卻有著這些意涵，下次沖泡咖啡時，觀察一下，每日的泡泡變化，也別有一番趣味。
These ordinary bubbles have special meanings during coffee brewing. When you brew coffee next time, please observe the bubbles changes daily, which is also interesting.
│延伸閱讀：手沖咖啡黃金比例
│Futher reading：Perfect Pour-Over Coffee Golden Ratio
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