Coffee knowledge course: whether it is pre-soaked or not is really related to whether coffee can be made well.

First of all, let's understand a problem: how to make coffee such as hand-brewed coffee and French pressure Philharmonic pressure coffee. These methods all require a process of soaking, which can also be understood as steaming. The function of steaming is to let the coffee powder fully contact with hot water before extraction, soak and expand. At this time, there is no real extraction of coffee. When we start water injection again, the pressure begins to be lowered, and the pressure begins to be pressed, the coffee liquid is separated from the coffee grounds. This is the real extraction stage (dissenting opinions are allowed, but it is easy to understand here as a comparison). Viagra often says that making coffee is an one-size-fits-all thing, and making most coffee is the same. So it is easy to understand whether or not to pre-soak when doing Espresso. At the beginning, soak the coffee powder in the powder bowl with a small pressure (some machines start with tap water pressure, while the machine in the water tank has no pressure) to make the coffee powder surface expand, so that the coffee powder surface is fully prepared when the higher pressure (usually 9bar) water comes.

To put it simply, the advantages of pre-soaking have two points: 1. Coffee powder surface fully absorbs water, but does not start the extraction, and so on when the 9bar water to extract is very high probability that all coffee powder particles can fully release aromatic substances. two。 Coffee powder surface water absorption expansion, will increase the contact area with the coffee machine water distribution network, and more closely, reducing the probability of extraction failure caused by uneven distribution of powder. Of course, Viagra does not say that it is not good without a pre-soaked coffee machine, because it can make good coffee without a pre-soaked coffee machine.

Let's talk about several pre-soaking methods of the general consciousness coffee machine:

1. Old-fashioned pull rod coffee machine

Prepreg has existed since the birth of espresso, and it is not a new thing invented in modern times. For the earliest pull-rod machines, the prepreg function was natural. When making coffee, pull down the pull rod (lever), lift the piston, the hot water enters the cavity and the filter bowl, and the hot water touches the coffee cake and begins to presoak, and the pull rod is not released until the desired pre-soaking time is completed. The piston begins to press down under the action of the spring to realize the extraction of coffee. In this way, the pressure of the pre-immersed water is the pressure given in the boiler, while the pressure of the extraction comes from the pressure of the tension rod spring, and the highest pressure should be about 9bar.

By the way, the pull rod machine does not need to relieve pressure, because when the piston reaches the bottom of the cavity, the pressure of the spring is already very small.

2.E61 type brewing head

When the motor drives the pump instead of the spring and piston, the barista can save a little time and energy. In order to achieve pre-leaching in a new way, people invented the E61's cooking head (of course, in addition to pre-leaching, E61 also has the function of using the thermosyphon effect to heat the head). The E61 head has a hollow system with pistons and springs. This mechanical system makes the pressure of hot water in the filter bowl build up slowly, thus achieving the effect of pre-soaking. The FAEMA E61 machine was still in use some time ago, the coffee product is really good, and the small mechanical lever brings a very cool feel. The electronic pump is controlled by a small pull rod, and the design is very ingenious. If the pull rod is not pulled, it will always soak or even extract coffee at a very low pressure. If you have a chance, you can play.

The E61 system does not have an electromagnetic pressure relief valve, and the pressure in the filter bowl is manually released by moving a small handle.

3. Electrically controlled coffee machine

In the 1960s, when automatic control technology was still expensive, E61 boiling head was an ingenious solution. Today, with the popularity of microelectronic technology, the realization of prepreg is a very simple thing, and the cost is much lower than that of E61. In the electronically controlled version of the machine, the prepreg generally works in two ways:

A) after pressing the production key, the pump starts to operate until the coffee is made, and the pressure relief cutting is first turned on (at this time, the pressure to enter the hot water in the filter bowl cannot be established), then turn off after the pre-soaking is completed, and then turn on the pressure relief until the coffee is made.

B) after pressing the production key, the pressure relief cutting is turned off until the coffee is made, and the water pump is operated briefly (when the hot water entering the filter bowl is less and the pressure is low), then pause until the prepreg is completed, and then start running again until the coffee is finished.

4. Hand-controlled coffee machine

What about the pre-immersion of the hand-controlled version? Experts do not advocate the manual way of "on-off-pause-on". In fact, the pressure of the pump is not established instantly, coupled with the fact that the water pipe entering the boiling head is very thin (or has a very thin section) and has a flow-limiting effect, so the water pressure in the filter bowl is also established step by step, and there is no need for artificial prepreg.

In fact, no matter which way of pre-soaking, the hot water is only in contact with the thinnest layer of coffee powder on the surface of the coffee cake in the filter bowl, not the whole coffee cake.

Source: Kang tasting Network