Why should I spray water before grinding coffee beans? Can RDT really make coffee better?

I believe that everyone has usually seen some "naughty operations" in coffee making on various media platforms or articles on Qianjie. For example, digging a small hole in the center of the coffee powder bed, or applying "acupuncture" to the coffee powder are all various auxiliary methods invented by the big shots in the industry to better make a delicious cup of coffee! In addition to these common daily methods, there is also an operation called "RDT", which can also help us make a delicious cup of coffee.

As we all know, coffee beans are very prone to static electricity during the grinding process. This is caused by the friction between the coffee bean and the blade and the uneven distribution of charge during the bean cracking process. When the coffee beans are roasted deeper (the lower the moisture content) and the finer the ground, the more static electricity will be generated through grinding. The existence of static electricity will cause the coffee powder to generate adsorption, and some coffee powder with finer particles and lighter weight will therefore be adsorbed on the larger particles and condensed into blocks.

After the coffee powder is agglomerated, its water-contacting surface area will be reduced, which will lead to a reduction in the extraction rate of coffee. At the same time, agglomerated coffee powder can easily promote the emergence of channel effects. Especially in the extraction of Italian coffee, there is a high probability that the water flow will bypass the agglomerated coffee powder and focus on extracting the surrounding areas with relatively loose texture. This will make the extraction of coffee very uneven, which is what we often call the channel effect. If we want to make a cup of coffee stably with a very large amount of agglomerated coffee powder, then we need to use some auxiliary means to eliminate the impact of static electricity. In addition to the cloth powder injection mentioned on the street two days ago, there is also the "RDT" implemented before coffee beans are ground.

The so-called RDT is the abbreviation for Ross Droplet Technique, which translates to "Ross droplet technology." It first appeared in 2005 at a coffee forum called "Alt.Coffee." Although it sounds very ambitious, in fact, all this method requires is to spray water on the coffee beans or moisten the coffee beans. With such a simple operation, we can reduce the occurrence of agglomerated coffee powder and reduce the chance of channel effects during coffee extraction. Because the person who invented this method is named David Ross, people call this method Ross Droplet Technique, or RDT for short.

At the end of the year before last, a new paper published by the University of Oregon in the journal Matter also confirmed this statement. Qianjie has also been verified through practice that spraying coffee beans with water can effectively reduce caking and reduce the adsorption of coffee powder. So we can know that RDT is indeed a feasible optimization solution. However, the RDT method still has certain drawbacks, which prevents it from being well used in daily products in stores. There are two main reasons. One is that RDT is only suitable for "single dose" coffee beans, which is difficult to use in batches. Because coffee beans have been wet since the water spray came into contact with them. Even if the speed is slow, the flavor substances in the coffee beans have begun to decompose, which makes us need to grind and use this moist coffee powder in a short time, otherwise the aroma of coffee will be greatly reduced.

Therefore, RDT is difficult to use in the case of a large amount of cups, because this will increase the cost of coffee production for a lot of time, and the efficiency will be greatly reduced. What's more, the main target affected by agglomerated coffee powder is espresso. For espresso, there are only a handful of stores that put in a "single dose" of coffee beans at a time. It's better to use a cloth powder injection to pour it out.

Secondly, RDT's water volume control requirements are actually relatively high. Spraying less will not have much effect. Spraying too much will make the coffee powder more likely to clump due to humidity. This agglomeration is even greater than the negative impact of static electricity. In addition, when the cutter head is in contact with water for a long time and is not cleaned in time, there is a probability that rust will occur. In other words, when we use it incorrectly, it is easy to lose the gain. Therefore, Front Street does not recommend using RDT without guarantees. If the amount of caked coffee powder is really very, very large and it is really necessary to use RDT to reduce the amount of caked, then the Front Street Association recommends using the method shared by James Hoffmann, the great god of the coffee world: by immersing the handle of the spoon in water, and then using the handle with water droplets to quickly stir the coffee beans. When the coffee beans are roughly evenly wrapped, you can start grinding. Otherwise, it would be safer to put powder injection ~

- END -