让咖啡口感更佳的科学研究

Scientific study on how to make coffee taste better

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.

煮咖啡并非尖端科学。但一项新研究表明，对于煮咖啡来说，拥有数学和分析化学背景并没有坏处。因为研究人员将材料科学和建模技术应用于煮咖啡后，获得了一个突破性发现与普遍观点相反，少量咖啡豆和更粗糙的研磨会让咖啡口感更稳定。他们的研究成果发表在《物质》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.

如果你是咖啡爱好者，无疑会发现有时浓咖啡的味道绝佳；而有时却不太令人满意。即使使用的是同一种咖啡豆、同一咖啡机和同样的设置。为了了解这一变化性，研究人员开发了一个数学模型，以探索当水冲过咖啡粉床时，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，我们是从写下仅适用于单个粉床的方程式开始。”朴茨茅斯大学的数学和物理高级讲师杰米·福斯特说到。这个任务不怎么吓人，因为在真实的咖啡粉床中有数百万颗粒以这种非常复杂的方式聚集在一起。

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，写出针对单个粉床的方程更容易解决。为了模拟整个咖啡床，福斯特及其同事将方程式复制了数百万次，再搅入一点数学知识，然后注入理论水模型显示，在理想情况下，在所有咖啡被所有水均匀接触时，实验应该出现期待的效果。

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.

俄勒冈州大学的计算化学家克里斯托弗亨登也是这项研究的参与者。他说模型充分描述了颗粒研磨的真实设置情况，即放入数量充足的大颗粒时，水就可以顺畅地流过粉床。但当人们将咖啡豆研磨得足够细时，就会发现预想的情况和模型显示的情况存在偏差。

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.

精细研磨咖啡豆后，咖啡口味有些比预想的浓郁。但有些味道却相当淡，这与传统观点背道而驰。传统观点认为，如果想让咖啡口味更浓郁，就要把咖啡豆磨得更细，因为这样粉床上的颗粒会更小。

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.

接触面积大，咖啡颗粒被萃取的速度就会更快。但研究人员的发现是如果研磨过度，最后的情况会是：颗粒变得过小，以致于堵住水要流过的缝隙。这实际上是阻碍萃取，而不是有助于萃取。同样的道理也适用于开始时的咖啡量，少一点的咖啡粉量最终尝起来也许会更有味道。

图片来源摄图网，版权归摄图网享有