What should I do if the filtration speed of cold extract coffee is slow? What efficient cold extraction filtration techniques are there?

It takes half a day to filter the cold extract for a moment. For those of you who like homemade cold coffee, have you also encountered such troubles: you thought it would be convenient to drink today last night, but in the process of separating the dregs, the coffee liquid flowed more and more slowly, more than ten minutes later, and the pot of cold extract had not been finished yet. You don't have to guess. The filter paper must have been blocked by fine powder again. What should I do?

The problem of the slow speed of cold extraction filtration can be said to haunt many friends. The workers who are in a hurry to go out are going to be late, but the liquid level does not drop for a long time, so they finally have to deploy more filter paper and filter cups to isolate the slag. It was not easy to filter the whole pot of cold extract.

The same degree of grinding

Why is the filtration speed of cold extraction so much slower than that of hands?

Compared with other rigorous parameters of high temperature hot water extraction, the compatibility of cold water immersion is very high. Under the condition of standing at low temperature, the concentration of coffee will change greatly unless it is greatly adjusted. Otherwise, the slight grinding difference will not cause a significant difference in the final taste.

In general, for the thickness of coffee powder used in cold extraction, Qianjie comparison recommends that we use a scale similar to that of hand grinding, that is, a medium fine degree (the screening rate of No. 20 sieve is about 70,85%, the EK43s bean mill has a scale of 910.5, and the hand mill C40 has a scale of about 20,22).

At this thickness, when we extract coffee by hand, we can usually handle the dripping time very well. taking the parameters of 15 grams of coffee powder, the ratio of powder to water at 1:15, and three-stage parameters, for example, the coffee can often be dripped in less than 2 minutes and 20 seconds. However, the same degree of grinding in the cold extraction of the filtration link, but far more than this time, why?

I don't know if you remember a comparative experiment in Qianjie, in which coffee powder with two different grinding scales was soaked in cold water, and other parameters remained the same. in the end, the concentration of coffee in the carefully ground group was even lower.

The reason is that the lighter fine powder particles are easy to absorb enough water first, and then the adhesion phenomenon occurs, which first reduces the extraction efficiency, weakens the taste of coffee, and when filtered by dregs, the clumps of fine powder particles will also take the lead to block the pores of the filter paper, making the water slower and slower.

Is there any way to solve it?

1. Use non-woven filter bag for cold bubble.

Cold extraction is nothing more than the simple steps of grinding powder, adding water, stirring, sealing, putting in the refrigerator, and filtering dregs, so if you want to get up without waiting, you can easily get a cup of iced coffee, we have to skip the patient part of the filter residue. According to the previous experience of cold extraction in the street, using a non-woven filter bag to cover the soaking of coffee powder is a good way.

Compared with the way that you have to wait for the filter slowly after soaking, using a filter bag to do cold extraction can really save a lot of trouble. A comparative experiment has been done in Qianjie, the coffee brewed from the filter bag can also have full flavor and tonality, and the fruit acid is even better than that soaked directly. It should be noted that the amount of powder soaked in a single tea bag should not be too much and should be controlled within 30 grams as far as possible, otherwise the water will not be able to come into contact with the internal particles, and finally the coffee will become light.

2. Can you directly filter the coffee liquid on the top layer without stirring?

Since the biggest "culprit" leading to the slow speed of cold extraction filtration is fine powder, some friends may wonder whether it can be solved by pouring out the light-colored liquid directly without stirring up the powder before filtration. In order to test this statement, Qianjie made two more pots of coffee to see if "not stirring" is feasible.

Coffee beans: 25g Santavini Water: 250g normal temperature Water (Nongfu Spring) Grinding degree: EK43s Bean Mill scale 9.5Lattice soaking time: 8 hours before soaking: all stir after soaking: one pot stir several times and then separate the residue / one pot does not stir, directly separate the dregs.

When directly comparing the two cups of cold extraction, we can see that the coffee without stirring the direct filter residue is much lighter than that after stirring, and the concentration is also the same (stirring group: 2.07%, non-stirring group: 1.75%).

The left is the mixing group, and the right is the non-mixing group.

In terms of taste, the unstirred Santa Veni cold extract has a light aroma, heavy water feeling, and almost no coffee flavor; as for the coffee filtered after stirring, the taste is obviously fuller, with the sour and sweet taste of passion fruit, grape, carambola and lemon, as well as round tea. Drink with ice to make it more refreshing and sour. Thus it can be seen that if you want the cold extract flavor to perform well, the action of "stirring" can not be saved.

3. Spread the coffee grounds at the bottom first, then filter them.

This is a small skill found in Qianjie when searching for materials, which comes from netizens with rich experience. The principle is to use larger coffee grounds as the medium to intercept the fine powder, so as to keep the gap of the filter paper unobstructed, so that there will not be serious blockage.

The operation steps are not complicated, the soaked cold extract should be fully stirred first, then rest slightly until most of the powder settles to the bottom, and then pour the upper liquid directly into a clean container to expose the bottom coffee grounds. At this time, we need to scoop out 2 tablespoons of powder, spread a layer in the filter paper, and then pour all the liquid into the filter cup and wait for it to filter.

After the trial in Qianjie, it is found that this method is indeed much faster than pouring it directly into the coffee pulp. A pot of cold extract with fine granulated sugar content about 250ml can be filtered in about a minute.

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