科学美国人60秒：咖啡磨太细，反而影响口感

This is Scientific American's 60-second Science. I'm Karen Hopkin.

这里是《科学美国人》的60秒科学。我是凯伦·霍普金。

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. [Michael I. Cameron et al., Systematically improving espresso: Insights from mathematical modeling and experiment]

做咖啡并非尖端科研。但一项新的研究表明，有数学和分析化学的背景也不错。因为研究人员将他们在材料科学和建模方面的技能应用于冲泡浓缩咖啡，并取得了一个突破性的发现：与普遍的看法相反，使用少量的咖啡豆和粗糙的研磨，会让咖啡口感更稳定。他们的研究成果发表在《物质》杂志上。[迈克尔-I-卡梅伦等人，《系统地改进浓缩咖啡：来自数学建模和实验的启示》。]

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.

如果你是一个咖啡爱好者，无疑已经注意到，有些时候，咖啡味道很好;有些时候，就不那么好。即使使用同样的咖啡，同样的机器，同样的设置。

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.

为了了解这种变异性，研究人员开发了一个数学模型，以探索当水通过咖啡粉床时，咖啡是如何被提取或溶解的。

“Basically, what we did was to start by writing down some equations, which apply to just a single ground.”

基本上，我们是从写下仅适用于单个粉床的方程式开始。

Jamie Foster, a senior lecturer in mathematics and physics at the University of Portsmouth.

杰米·福斯特，朴茨茅斯大学数学和物理学高级讲师。

“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. And so a more tractable problem is to write down the equations on a single ground.”

所以这是一个不那么可怕的任务，因为在真正的咖啡床中，有数以百万计的颗粒，它们以这种非常复杂的方式聚集在一起。因此，写出针对单个粉床的方程更容易解决。

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.

为了对整个咖啡床进行建模，福斯特和他的同事们将这个方程复制了数百万次，再搅入一点数学知识，然后注入理论水。

“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.”

模型显示，在理想情况下，在所有咖啡被所有水均匀接触时，我们应该期待的效果。

Christopher Hendon, a computational chemist at the University of Oregon, who also took part in the study.

克里斯托弗·亨登，俄勒冈大学的计算化学家，他也参与了这项研究。

“And indeed, 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 you grind sufficiently fine, that’s when we started to see, in real life, a divergence from the expectation that the model was telling us.”

事实上，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。但当把咖啡豆研磨得足够细时，就会开始发现，你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.

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。

“The thinking, if you want a stronger cup of coffee, is, well, I’ll grind it finer, because by doing that, I’ll have smaller particles in my grounds, and the smaller particles will have a higher surface area. And so this high surface area allows for more rapid extraction from the grains”

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，继而接触面就更大。接触面积大，咖啡颗粒被萃取的速度就会更快。

But what the researchers found is ...

但研究人员发现...

“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.”

如果过度研磨，最终发生的情况是：颗粒太小，事实上，它们堵塞了水要流动的缝隙。而这实际上阻碍了萃取，而不是有助于萃取。

And the same is true for the amount of coffee you start with—so that less can, counterintuitively, end up tasting like more.

对于所使用的咖啡量来说，也是如此——因此，反其道而行之，少量的咖啡，也能尝起来像更多。

“Since this article came out, there has been a tremendous amount of activity on Twitter—arguing, discussing, just general excitement and interest in the project. And independent of whether this helps make more reproducible coffee or not, this is a tremendous success—that we have got millions of people to have read a scientific article and engage with science. That’s a great success for scientific literacy.”

自从这篇文章发表后，Twitter上出现了大量的活动，人们对这个项目进行争论和讨论，这表明了人们对其的普遍兴奋和兴趣。无论是否有助于制造口味更具可复制性的咖啡，这都是一个巨大的成功，因为我们让数百万人阅读了科学文章，参与了科学研究。这对科学素养来说是一个巨大的成功。

And we can all drink to that.

我们都可以为此干杯。

Thanks for listening for Scientific American's 60-second Science. I'm Karen Hopkin.

感谢收听《科学美国人》的60秒科学。凯伦·霍普金报道。