Coffee connoisseurs have long held the belief that adding a little water to the beans before grinding them could make a difference. A new study by researchers at the University of Oregon seems to confirm exactly why.

The research explored how the technique, which started as an attempt to address the often messy coffee-making process, also affected flavor.

“When you grind coffee, it goes everywhere,” said study coauthor Christopher Hendon, an associate professor of computational materials chemistry at the University of Oregon. “Dust comes out of the grinder, it’s like a plume that covers everything. But if you add a little water, it seems to not go everywhere. It’s cleaner. That was the primary reason people did it.”

The mess is caused by static electricity, which is created by friction when the beans are smashed together. This static charge then makes the particles of ground coffee repel each other — like magnets of the same polarity — sending them off in every direction. Water acts like an insulator, dampening this effect — a process known as the “Ross droplet” technique. “It was first proposed by some enthusiast on a home barista forum,” Hendon said. “The idea has been around for several years, and originally it was borrowed from the materials production industry, like wood pulping.”

However, what started out as a way to reduce mess slowly morphed into a more sophisticated way to obtain a better brew — or at least so people thought. The theory was that by reducing static electricity, water not only kept the ground coffee from flying around or sticking to the insides of the grinder, it also prevented microscopic clumps from forming during brewing. Why are clumps bad? Because water flows around them, leaving untouched coffee — and therefore flavor — behind. In barista parlance, they decrease extraction yield, or the amount of coffee that ends up in the cup, dissolved in the liquid.

“If you have clumps forming, there’s going to be significant amounts of void space, kind of like when you stack watermelons,” Hendon said. “As a result when you push water through you end up with less surface area touching the water and therefore lower extraction.”

The study, published Dec. 6 in the journal Matter, tested this more subtle, harder to see potential benefit of adding water to the beans: getting rid of flavor-robbing microclumps. François Knopes of the Independent Coffee Lab, a professional coffee roaster and taster who was not involved with the study, said he routinely sprays his beans before grinding for tasting evaluation and would recommend doing so to anyone in a home setting. (SD-Agencies)

Words to Learn 相关词汇

【演变成】yǎnbiàn chéng morph into gradually change into

【说法】shuōfǎ parlance a formal word that means a group of words or style of speaking used by a particular group of people

长期以来，咖啡品鉴师们一直认为，在磨豆之前加一点水可以让咖啡变得与众不同。俄勒冈大学研究人员的一项新研究似乎证实了这一点。

研究探讨了加水是如何影响咖啡风味的，这种方法起初是为了解决咖啡制作过程中粉末乱飞的问题。

这项研究的共同作者、俄勒冈大学计算材料学副教授克里斯托弗•亨登说：“研磨咖啡时，咖啡粉会到处飞。粉尘从研磨机里出来，弄得到处都是。但如果你加一点水，粉尘不会四处飞散，就更干净了。这是人们磨豆之前加水的主要原因。”

这是由静电造成的，豆子一起摩擦时产生静电，让咖啡粉颗粒像极性相同的磁铁一样相互排斥，向各个方向散开。

水把咖啡豆包裹起来，可以抑制这种效应 —— 这被称为“罗斯液滴”技术。亨登说：“最早是某个咖啡爱好者在家庭咖啡师论坛上提到这种做法。它已经存在好几年了，最初是从材料生产行业借鉴过来的，比如木材制浆。”

起初只是防止粉末飞散，后来慢慢演变成了一道用来获得更好的冲泡效果的工序 —— 至少大家这么认为。当时的理论是，通过减少静电，水不仅能防止咖啡粉四处飞散或粘在磨豆机内部，还能防止咖啡在冲泡过程中形成微小的结块。

结块为什么不好？因为水从它们周围流过，部分咖啡没接触到水，味道也就没出来。用咖啡师的话来说，结块会降低萃取率，即最终留在杯中溶解在液体中的咖啡量。

亨登说：“如果咖啡结块，就会产生大量的空隙，就像把西瓜叠在一起。因此，当你把水压过咖啡粉时，粉末接触水的表面积减少，从而降低萃取率。”

这项于12月6日发表在《物质》杂志上的研究测试了向咖啡豆中加水更微妙、更难察觉的好处：防止破坏咖啡风味的微结块。

独立咖啡实验室的弗朗索瓦•克诺普斯是一名专业咖啡烘焙品鉴师，没有参与这项研究。他说，自己经常磨豆前喷点水，以便更好地品鉴咖啡，并建议大家在家里也这样做。

(Translated by Debra)