Bean grinder: on the importance of bean grinder in extraction the technology of making a cup of coffee

No matter what kind of extraction method we use, what kind of coffee beans and equipment we use to make a cup of coffee, the grinding quality plays a key role from beginning to end. Many novice beginners pay great attention to how to choose equipment and equipment, pay attention to brewing methods, but often underestimate the importance of the influence of bean grinders on products.

Little do you realize that a good cup of coffee that can really be called a high-quality coffee should be indispensable for making "beans, technology, grinding and machine".

It is also an urgent task for beginners to understand as soon as possible what factors the bean grinder has on the product.

The reason why we don't say "what is good" but take "how to understand" as the theme of this article is also from the point of view of the public. After all, it is unconvincing to state the facts in the form of "a certain type of cutter head structure grinds more evenly" or "a certain type of bean grinder has better flour quality".

Over time, people will think more and more about "Why on earth is it better?" How can the performance of a bean grinder be distinguished? "

In this paper, we will first put aside the explanation of dynamic facts such as "differences in grinding powder with different structures" and "comparing the flour quality of two bean grinders", and sort out the influence of bean grinders in extraction one by one. I hope it can give some guidance to those who have not yet understood the definition of bean grinder.

Time is limited, let's get to the point.

Rigidity conditions for determining milling quality (1): uniformity

The working principle of the coffee grinder is that the inner cutter head of the grinder is driven by an electric motor to rotate at a high speed, and the coffee beans entering the inner and outer knife through the bean warehouse are divided into fine particles and become the coffee powder we need to brew.

The fineness of grinding is determined by the distance between the upper and lower cutterheads before grinding.

The farther the knife distance is, the thicker the grinding powder is, and the closer the knife distance is, the finer the grinding powder is. generally, the dial or knob is used to adjust the thickness.

The actual purpose of what players often say that "different utensils need different powder thickness" is to make the thickness of coffee powder correspond to the extraction principle of a certain kind of apparatus, and adjust it according to their own techniques, so as to reduce the possibility of excessive or insufficient extraction and achieve a relatively better effect.

When you find the right powder size, consider the next important factor: uniformity.

The grinding process of each cup of coffee usually takes a few seconds to more than ten seconds. According to the fineness of grinding powder required by different brewing methods, the grinding machine grinds each coffee bean into about 100,3500 coffee beans with a particle diameter of about 0.05~0.7mm. When extracting so many coffee particles, the influence of uniformity on the product is extremely critical.

What is extraction? The definition of extraction itself refers to a process of substance exchange between coffee powder and water.

Put aside what we often say, "if you don't grind evenly, you can't make coffee well." from a more macro point of view.

The taste of a cup of coffee is originally a combination of thousands of coffee granule extracts.

When the fluctuation value of grinding thickness is large, most of the particles can not reach the uniform degree we want.

As a result, under the same extraction conditions, the coarser coffee particles are more likely to be underextracted, while the finer particles are overextracted in advance.

Therefore, the larger the grinding span of coffee powder is, the more turbid and irritating smell can be tasted.

On the other hand, coffee powder with basically the same size and similar shape is used for extraction.

The taste becomes brighter and stronger, and the performance of flavor characteristics is clearer and consistent.

In Italian concentrated extraction, whether the degree of grinding is uniform or not not only affects the taste of the product, but also determines the success of Italian coffee.

If Italian production is carried out with a bean grinder with poor uniformity, it is easy to make the powder particles distributed in a certain part (or possibly more than one part) of Coffee pressed powder thicker, and the high-pressure water flow will quickly squeeze out of these thinner "vulnerabilities" of pressed powder, creating one or more channel effects so that the local coffee powder is overextracted while the surrounding part is underextracted. In this state of Italian extraction, it will only be a cup of bitter water.

When the grinding quality of a bean grinder is seriously lower than the uniformity required for making Italian style, no matter how fastidious the cloth powder is and no matter how good the powder pressing skill is, it is difficult to successfully make a qualified Italian style. Because the technology of powder distribution and powder pressing itself is based on the premise that the powder is uniform enough.

Therefore, if you want to get a better flavor in the cup,

A well-powdered bean grinder will bring about far more improvement than you can imagine.

Rigidity conditions for determining milling quality (2): fine powder content

Fine powder refers to coffee powder with very fine particles, also known as flour and ultra-fine powder.

Fine powder will inevitably exist in the grinding process.

When the proportion of fine powder exceeds a certain degree, it will aggravate the bitterness and miscellaneous taste, and have an adverse effect on the product.

Too much fine powder has a particularly serious effect on the taste of the product when using the French kettle.

A large amount of ultra-fine powder will pass through the filter, making the coffee drink muddy, as if it were imported with soot and wood dregs.

We usually choose the coffee powder with coarser grinding fineness, or directly upgrade the higher density filter screen for pressure production, in order to reduce the production of fine powder.

When it comes to the production of espresso, when the flow rate of Italian concentrate is relatively slow, and the oil is rich, the fine powder will not sink directly into the coffee liquid, but slowly spread and float on the surface of the oil. to form a beautiful "tiger pattern spot"

In other words, the tiger pattern is actually a very fine powder that passes through the filter hole of the powder bowl.

This is why it is easier to produce tiger spots by gently pressing pressed powder or using a bean grinder with a conical knife structure.

However, no matter whether the tiger pattern exists or not, it can not represent the quality of a cup of Italian production.

Some players exaggerate the influence of tiger pattern, and some even think that "tiger pattern is a good performance of Italian extraction."

I can't agree with this.

Too much fine powder will cause the dead point of pressed powder which can not be extracted, form the channel effect, and seriously affect the success rate of Italian extraction.

So, does fine powder do more harm than good to the taste of coffee?

In an early article of Brother Bird, "also talking about the sieving method of single Coffee Powder", comparing the screening of fine powder with the two cups of coffee that are normally ground, the level of production after sieving powder is weak, the sweetness is weakened, and the connection carrier between flavors is lost. it also makes the flavor structure greatly reduced.

The coffee which has completely lost the fine powder can be said to be empty and boring.

Therefore, the existence of a small amount of ultra-fine powder is inevitable and necessary.

An excellent bean grinder can control the amount of fine powder in a small range and reduce its adverse effects.

Other factors affecting the quality of grinding (1): grinding heat

During the working process of the bean grinder, the cutter head produces a certain amount of heat with the high-speed grinding.

Coffee powder will volatilize the aromatic substances ahead of time due to a large amount of heat, resulting in the loss of part of the flavor and aroma.

The heating problem of grinding is mainly caused by the heating phenomenon of Italian bean mill, because the grinding is fine and the friction between the grinding plate and coffee beans is strong, in the case of a small amount of domestic grinding, the effect of heating on the quality of flour is almost negligible. On the other hand, when the bean grinder is used as a commercial place for business or for rapid continuous grinding (such as during the adjustment of scale), the heating of grinding is destructive to the flavor of coffee to a certain extent.

The calorific value of the cutter head depends on many factors, such as the size of the grinding plate, the material used, the structure of the knife, the fineness of grinding, the speed of the motor, the hardness and texture of coffee beans and so on.

Almost all high-end Italian bean grinders are equipped with heat dissipation windows, cooling fans, or higher torque and low speed motor to drive the cutter head, in order to reduce the number of cutterheads.

And the simplest and most effective solution to eliminate grinding heat is to upgrade your bean mill.

Other factors affecting milling quality (2): generation of static electricity

Static electricity is a common phenomenon in the grinding process of coffee powder, and there are many reasons for it.

Compared with the first three, the effect of static electricity on the product is minimal.

But many people still know very little about it. Wolf simply explains it here.

Static electricity usually occurs from the following factors:

The finer the grinding and the faster the grinding, the stronger the static electricity produced.

The internal material is plastic, and the lower powder mouth does not use a bean grinder designed to reduce static electricity, which produces stronger static electricity.

The coffee beans with rich oil and deep roasting degree are ground to produce stronger static electricity.

Static electricity will have some indirect effects on the quality of milled products.

For example:

The powder outlet of the bean grinder accumulates residual powder and blocking powder.

When making hand punching or Italian concentration, the powder is agglomerated, which makes the cloth powder uneven.

Part of the silver skin and ultra-fine powder produced by adsorption and grinding

Timing data affecting the type of electronically controlled quantitative machine

Properly increasing the humidity of the room is also a way to improve the generation of static electricity.

Source:

Gary's blog