The principle of steaming? what is steaming?

About the steaming of coffee. Many baristas or enthusiasts have different opinions on the way, time and amount of steaming, and learn the process of steaming from the physics of steaming in coffee making. When the coffee bean is ground into a coffee powder, the coffee powder we can see with the naked eye is a whole, but in fact, the microstructure of the coffee powder is actually similar to that of a honeycomb, with countless penetrating holes in it. Carbon dioxide is constantly released from freshly roasted coffee beans, and much of this carbon dioxide is initially stored in these holes in the coffee beans.

Just imagine, hot water is poured directly and at high speed on such a coffee powder, the hot water will be extracted close to the periphery of the coffee powder, and the internal carbon dioxide is blocked by water and cannot be eliminated. And because there is carbon dioxide in the powder, the hot water can not seep into the coffee powder. So hot water will only constantly wash the surface of the coffee powder, resulting in excessive extraction on the surface of the coffee powder, but not on the inside.

So the purpose of steaming in coffee is to help coffee powder discharge carbon dioxide smoothly. In order to achieve this goal, the amount of water needed must be the right amount, and gently let the water stop on the coffee powder and let it squeeze into the coffee powder to force the discharge of carbon dioxide to ensure the smooth extraction. For hand flushing with this production method, the amount of steaming water is the best to master. The amount of steaming water is just enough to soak the powder layer until the lower edge of the powder layer begins to drip. But at this point, there are high requirements for the way of water injection, which requires that water injection must be gentle, stable and fast, and it is best that the surface of the foggy powder layer does not blister. Because if blisters, it means that the local high water injection leads to the flow directly through the powder layer flow, and the powder particles are not evenly immersed in water.

At this point, the coffee powder layer has been fully soaked, and water begins to seep into the coffee powder to squeeze out the carbon dioxide. We can obviously see that the powder layer begins to swell and the carbon dioxide is constantly discharged, but if when is the best time to inject water again, it is the moment when all the carbon dioxide is discharged and the coffee powder layer begins to collapse. But it really needs to be observed very carefully when it collapses, but if you can't observe it for the time being, we suggest that the newer the coffee beans, the longer the steaming time. For example, the steaming time of roasting overnight is even 45-50sec, the coffee beans can be reduced to 30-35sec after three days, and the steaming time of coffee beans after a week is probably only 20sec. If the coffee beans for a long time can not be bulged after water injection, it is recommended to cancel steaming and direct secondary water injection.

Similarly, for the equipment such as pressure kettle, electric drip filter, love pressure and so on, we also hope that the relatively new coffee beans can be extracted more efficiently by adding steaming process, and the amount and time of steaming can be properly referred to by hand, but the amount of steaming water under pressure should be reduced appropriately.