讓咖啡口感更佳的科學研究

Making a cup of coffee isn't rocket science. But a new study shows that a background in math and analytical chemistry doesn't hurt. Because researchers who applied their skills in materials science and modeling to brewing espresso have made a grounds-breaking discovery: contrary to popular belief, using fewer beans and a coarser grind will give you a more consistent shot. Their work appears in the journal Matter.

煮咖啡并非尖端科學。但一項新研究表明，對于煮咖啡來說，擁有數(shù)學和分析化學背景并沒有壞處。因為研究人員將材料科學和建模技術(shù)應用于煮咖啡后，獲得了一個突破性發(fā)現(xiàn)與普遍觀點相反，少量咖啡豆和更粗糙的研磨會讓咖啡口感更穩(wěn)定。他們的研究成果發(fā)表在《物質(zhì)》期刊上。

If you're a coffee aficionado, you've no doubt noticed that some days, you may get a great espresso; other days, not so much. Even with the same coffee, the same machine, the same settings. To understand that variability, the researchers developed a mathematical model to explore how coffee is extracted or dissolved as water passes through the bed of grounds.

如果你是咖啡愛好者，無疑會發(fā)現(xiàn)有時濃咖啡的味道絕佳；而有時卻不太令人滿意。即使使用的是同一種咖啡豆、同一咖啡機和同樣的設(shè)置。為了了解這一變化性，研究人員開發(fā)了一個數(shù)學模型，以探索當水沖過咖啡粉床時，咖啡被萃取和溶解的方式。

“Basically, what we did was to start by writing down some equations, which apply to just a single ground, ” said Jamie Foster, a senior lecturer in mathematics and physics at the University of Portsmouth. So it's a less intimidating task, because in a real coffee bed, you've got millions and millions of particles that are packed together in this very complicated way.

“基本上，我們是從寫下僅適用于單個粉床的方程式開始。”樸茨茅斯大學的數(shù)學和物理高級講師杰米·福斯特說到。這個任務(wù)不怎么嚇人，因為在真實的咖啡粉床中有數(shù)百萬顆粒以這種非常復雜的方式聚集在一起。

So a more tractable problem is to write down the equations on a single ground. To model the entire coffee bed, Foster and his colleagues copied that equation millions of times, stirred in a bit more math and then poured on the theoretical water. The model tells us what we should expect in an ideal situation when all of the coffee is being contacted by all of the water equally.

因此，寫出針對單個粉床的方程更容易解決。為了模擬整個咖啡床，福斯特及其同事將方程式復制了數(shù)百萬次，再攪入一點數(shù)學知識，然后注入理論水模型顯示，在理想情況下，在所有咖啡被所有水均勻接觸時，實驗應該出現(xiàn)期待的效果。

Christopher Hendon, a computational chemist at the University of Oregon, who also took part in the study, said the model describes reality very well for particular grind settings, where there is a sufficient amount of large particles so the water can flow freely through that bed. But when people grind them sufficiently fine, that's when we started to see a divergence from the expectation that the model was telling us.

俄勒岡州大學的計算化學家克里斯托弗亨登也是這項研究的參與者。他說模型充分描述了顆粒研磨的真實設(shè)置情況，即放入數(shù)量充足的大顆粒時，水就可以順暢地流過粉床。但當人們將咖啡豆研磨得足夠細時，就會發(fā)現(xiàn)預想的情況和模型顯示的情況存在偏差。

With the fine grind, some shots were stronger than predicted. But some were considerably weaker, which flies in the face of conventional wisdom. The thinking, if you want a stronger cup of coffee, is if we grind it finer, the smaller particles will have a higher surface area.

精細研磨咖啡豆后，咖啡口味有些比預想的濃郁。但有些味道卻相當?shù)?，這與傳統(tǒng)觀點背道而馳。傳統(tǒng)觀點認為，如果想讓咖啡口味更濃郁，就要把咖啡豆磨得更細，因為這樣粉床上的顆粒會更小。

So this high surface area allows for more rapid extraction from the grains. But what the researchers found is if you kind of overdo the grinding, what ends up happening is: the particles are so small, in fact, that they kind of clog up the gaps where the water's trying to flow. And that actually hampers the extraction rather than helping it. The same is true for the amount of coffee you start with-so that less can, counterintuitively, end up tasting like more.

接觸面積大，咖啡顆粒被萃取的速度就會更快。但研究人員的發(fā)現(xiàn)是如果研磨過度，最后的情況會是：顆粒變得過小，以致于堵住水要流過的縫隙。這實際上是阻礙萃取，而不是有助于萃取。同樣的道理也適用于開始時的咖啡量，少一點的咖啡粉量最終嘗起來也許會更有味道。