A brief discussion on coffee extraction: what conditions and tools are needed? Do I need to extract all 30%?

Preface

In previous articles, we talked about how to choose a grinder and a coffee machine. Of course, such articles are not popular and will be difficult to circulate.

It is obviously easier to persuade people to consume rationally according to their own needs rather than to persuade them to consume impulsively.

However, I still believe that single-dose and single-head coffee machines will gradually increase in the future coffee market, and there will be more and more thoughtful coffee shops because there will be more and more thoughtful people.

Such a coffee shop will be the most rational and gentle in the coffee industry.

Let’s talk about coffee extraction today!



I often hear baristas say:

“This cup of coffee is under-extracted”

“This coffee is over-extracted”

…

So what exactly is extraction? Is there a clear answer?

some!

70% insoluble fiber and carbohydrates + 30% water-soluble substances = coffee beans

The process of extracting these 30% water-soluble substances is called extraction.

How do we extract it? What conditions and tools are needed? Do we need to extract all 30%?

Let’s discuss these issues together today.



Extraction requires several key conditions: water, grinder, and coffee machine.

First of all, it is water. We know that 30% of water-soluble substances need to be hydrolyzed, so they definitely need to rely on water. A cup of coffee is 98% water. I would like to explain water to you first.

Sometimes the coffee you drink abroad is different from that in China, and even if you bring foreign coffee beans back home, the taste will be different after brewing. This is a very normal thing. When you rack your brains to find the right answer, you don’t realize that it is just because of the different water quality.

The following is the "Health Standard for Drinking Water" (GB5749-2006) implemented in my country in 2012.



I want you to see how our domestic water reaches our coffee shops and homes.



You will find that, oh! After filtering out the sand and gravel, the water plant will disinfect it with chlorine and then transport it to our homes and coffee shops through "long pipes".

Although my country's tap water quality index is very high, pollution incidents are reported in the newspapers very frequently. There are two main reasons for this:

1. The local government failed to meet the targets as per the standards.

2. Secondary pollution caused by water pipeline transportation.

If it is just hand brewed coffee, we can use boiling water. Most coffee shops will choose automatic water supply for espresso machines (I personally use a water tank device)

If the water is automatically inlet, then you must purchase a water purifier. The question is, which water purifier is better? (Water purifier advertising space for rent here)

The following are the "water for coffee" recommendations given by SCAA (Specialty Coffee Association of America). Last night, I discussed the issue of TDS (total dissolved solids) with Nongfu Spring's technical director. Regarding the 150mg/L indicator, we only use it as a reference.

The most important thing is clean, clean, clean! (Secondary contamination of water purifiers is the most serious problem. When purchasing a water purifier, you must compare the performance, price, and filter replacement frequency in detail.)

The joke in the water industry is: Actually, I don’t sell water purifiers, I sell filter cartridges



When we have very clean water, we cannot directly hydrolyze the soluble substances in coffee beans. Why?



Because the contact area between water and coffee beans is too small, hydrolysis is very limited, so we need to use a knife to grind the coffee beans into powder to increase the contact area between water and powder, thereby hydrolyzing more water-soluble substances!



(It may take a long time to sharpen with this kind of knife...)

Technology makes people progress, and we will use coffee grinders.



This is a pair of blades from a coffee grinder. The two blades work together to grind the coffee beans into powder flakes, thus helping to hydrolyze soluble substances.



The question is, how much powder do we need?

If you are using an 18g powder basket, you can try 5g-20g, but there is a general principle here - the amount of powder you use is not only determined by your powder basket, but also by the water distribution network of your coffee machine. That is to say, the amount of powder you use cannot be so much that it touches the height of the water distribution network of the coffee machine.

How can you make sure that the coffee powder touches the water diversion net when the handle is buckled on the coffee machine?

It's very simple. Put the handle on and then take it off to see if the powder is still intact. If you want to know how much space is left between the water-dividing net and the powder, you can put a coin on the powder, then put the water-dividing net on and then take it off, and judge the size of the gap by the dent on the coin.

The amount of powder determines the output of espresso to a large extent (I personally like a large powder bowl with less powder, such as the 21g powder bowl of La Ma corresponds to 17g or 18g of powder)

The weight of the espresso liquid (e.g. 40g) obtained by brewing a specific amount of powder (e.g. 18g) through a coffee machine is called the powder-to-liquid ratio (1:2.2).

So, how much liquid do we use for a cup of espresso? The traditional definition is 25-30 grams, but such espresso is too concentrated and stimulating. According to a questionnaire survey of foreign coffee shops, more and more baristas are starting to increase the powder-liquid ratio. 30g-50g is very common, which was very unorthodox in the past.

Although everyone's taste may be different, the SCAA recommends the best extraction rate: 18%-22%. However, relying on this framework, more possibilities can still be found.

Speaking of this, it is said in the industry that espresso will bring bitterness and off-flavors in the later stage. Generally, when espresso has bitterness and off-flavors, most people’s first reaction is: over-extraction!

I personally think that this judgment is a bit of a "simplistic attribution". First of all, the latter part does not necessarily bring bitterness and off-flavors.

Many baristas choose to pinch off the tail, but I think this destroys the integrity of a cup of coffee.

Speaking of the "back end", is the end of the espresso considered the back end? If it is just because there is too much liquid that it will feel bitter, then I have used 18 grams of powder and extracted several hundred grams of espresso in less than 30 seconds (espresso simulated hand-poured) and I did not taste any foreign flavors, so it is a bit biased to emphasize the back end.

"Backend" is an ambiguous term, I prefer to use "framework".

Another example: when coffee tastes sour, most people attribute it to under-extraction, because in their impression, acid tends to appear in the front. Some people also think it is over-extraction, because sometimes you spend 40 seconds to extract espresso and it still has a strong sour taste.

So is it under-extraction or over-extraction?

More reasons: uneven extraction.

When water passes through coffee powder, due to its own inertia, it passes through the places where it is easy to pass, but less places where it is difficult to pass. This causes the soluble substances in the coffee powder in the powder bowl that come into contact with water to be hydrolyzed at a wrong speed, resulting in a very strong and difficult to swallow "acidic espresso".

.



So what is the purpose of extraction? Simply put: to find the sweet spot of espresso.

Once we have determined the required amount of powder and the output, the only condition that needs to be determined is time.

How much time is needed to reach the target yield of the specified amount of powder is the most important point in the espresso process. We will adjust the time by changing the coarseness of the coffee powder, so a term is derived here: grinding adjustment (adjusting the scale of your grinder)

We can adjust the distance between the grinder's blades and change the coarseness of the coffee powder by turning the grinder's dial, but the question is: will the grinder change its distance as we wish every time we make a fine adjustment?

Therefore, many coffee grinders claim to have: infinite fine-tuning!

But here comes the problem. Sometimes you turn the screws around but the parameters don’t change, or even the parameters themselves become out of order (for example, you coarsen the grind but the flow rate becomes slower). This is very puzzling.

I want to tell you a sad fact: not all coffee grinders can produce powder that is faithful to the grind!

The technology of infinite fine-tuning does not exist alone. For example, the Mythos one, which I think is the most convenient "continuous cup grinder" at present, has infinite fine-tuning that is equivalent to an aircraft carrier, and its escort ships include: inclined titanium blades, ultra-short powder channel, and constant temperature system.

Every function serves its infinite fine-tuning. (Even so, after adjusting the grind of Mythos One, I still recommend clearing a handful of powder. Even with such a short powder path, there will still be a lag of about 1 handful, not to mention other grinders.)

With the help of the constant temperature system, the particle size of coffee powder is ground more stably. The combination of all these functions truly achieves the pleasure of "point where you want, and grind there" grinding.

By the way, I think the best infinite fine-tuning technology currently lies in the Italian Eureka grinder brand, but it was acquired by Nuova, and the mythos one grinder produced by Nuova is actually largely based on Eureka (but unfortunately Eureka is very unpopular in China!)

Back to the point, if you like to adjust the grind, I suggest you buy a precision grinder (I personally like to use those "straight-out" or ultra-short powder path grinders for espresso recently: such as EK, MCD4, 270... I would like to talk to you about the evaluation of different grinders if there is a chance)



Since we are just briefly discussing extraction, I think that’s about it.