Cold Brew coffee is traditionally made by steeping coffee grounds contained in some type of filter/mesh for 12-48 hrs in cold or room temperature water. This process results is a smooth and concentrated coffee that is different in taste, feel, and smell than hot brewed coffee. Cold brew takes longer to brew because the solubles in the grounds are not released as fast in colder temperature water. They are also different solubles than you would get when brewing hot coffee. This is why cold brew taste different. The hot water can pull the solubles out faster, but it also degrades/oxidizes the solubles making them more bitter and acidic than cold brew. A longer description of the differences can be found here.
The Swift cold brew device (Patent Pending) is a completely new process that can brew cold brew coffee in as little as ten minutes. The key difference is the extraction method. Colder or room temperature water is still used which results in the same solubles as normal cold brew being released. During the normal 12-48 hr. steep the water slowly moves at a molecular level through the grounds and filter releasing the solubles at a certain rate. This rate and number of solubles released can be increased if agitation and energy is introduced. This is where the Swift cold brew device excels. The device moves the water from the bottom of a container through the device back to the top of the grounds/filter mesh using a pump. This process forces the water through the grounds at an accelerated pace. The cycle repeats for 10 minutes taking the water from the bottom back through the grounds over and over again. A fresh cup of cold brew results. A more concentrated cup can be made through a longer cycle time or a higher coffee ground to water ratio. A picture of the process is shown below.
You can visualize the science of this process by thinking about how salt dissolves in a glass of water. In the description below, you can think of the coffee ground solubles as the salt. Left to sit for a while, a salt block will dissolve similar to how the solubles in coffee are eventually released. Stirring increases this rate, similar to how the Swift cold brew device moves the water to increase the rate. However, the Swift device moves the water vertically through the grounds. This provides a further increased rate of extraction compared to a traditional circular stirring motion.
“In order for a solute to dissolve, the water molecules (or the solvent molecules, in general) must come into contact with the solute particles. For example, in the salt example, the water molecules must be able to interact with each ions. Stirring exposes more of the solute, and makes more of the solute come in contact with the solvent, thus increasing the rate of dissolution. Put in another way, stirring brings “fresh parts” of the solute into contact with the solvent. If you simply leave a chunk of salt in the middle of a glass full of water, the dissolution will be slow as initially, water can only interact with the particles that are on the surface of the block of salt. If you stir the system, however, you are exposing not only those in the surface, but also the other particles in the bulk of the salt, and hence water can come into contact with them and dissolve the particles simultaneously. “