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Are you afraid of the "sour" in coffee?

Introduction: Perhaps you will fall in love with the sour coffee that you are afraid of.

On a sunny morning, you go to a cafe to order a cup of coffee and take a sip. You get a mouth full of “sourness.” How would you react?


Nowadays, more and more cafés are appearing in the streets of cities and there is more and more abundance of coffee drinks that are offered by different styles of cafes.

The coffee drinks that we have tasted no longer only bitter. There is also more and more "sour" coffee as well as many fruity type of coffee. It makes some consumers who do not like sour drinks have do not know what to choose.


The "sourness" that many specialty coffee people love, has made many consumers want to avoid. Is "sour" coffee that terrible?

Random survey

We randomly interviewed dozens of coffee consumers in various industries and asked them about their attitude towards “sour” coffee. We compiled several interview records that can represent the majority as follows:


We are finding that even in the city of Pu’er where people love eating sour food like sour papaya and sour mangoes still many consumers cannot accept the acidity in the coffee.


The reasons are roughly the following three:

1. The traditional impression of dark roasted coffee makes people think that coffee should be bitter. Connecting sourness with food rottenness.

2. The bad acid in the coffee is too irritating and unacceptable.

3. The person’s stomach cannot handle sour coffee.

It can be seen that two-thirds of people are not really unable to accept sour coffee because they have not drunk a cup of good quality sour coffee. Some people have not even tried it out leaving no reason not to like it. Serving in the store, most baristas will respect the customer's choice. If you say that you don't like sour coffee, they will not recommend any fruity-type coffee for you. Maybe you will lose the chance to encounter a good cup of coffee.


If your stomach can take it and you are not a person who refuses sourness, we encourage you to find a cup of good quality, sour coffee that you love.


The coffee cherry is fruit.

The coffee tree belongs to the Rubiaceae genus. When the coffee cherry is ripe, it is like a red cherry. It doesn’t have much pulp but it is very sweet. Unlike other fruits, coffee beans(seeds) are the core of the fruit thus it is reasonable to have acid in the coffee.


In the early days, people mostly drank coffee for it’s caffeine and did not care about the flavor. Many roasters roast coffee till it’s dark because it is beneficial for the preservation and stability of coffee. Therefore the impression that "coffee is bitter" has also imprinted in people's minds.

Coffee varietal and growing conditions.

We find that many coffee advertisements would use the words “high altitude” and “Arabica varietal.” There are reasons why businesses list these words as a symbol of good coffee.


Coffee is grown in tropical and subtropical regions and the higher the altitude, the greater the temperature difference between day and night. The coffee ripening cycle is lengthened and there is more time for respiration to produce flavors within the coffee beans.

A variety of high-quality organic acids such as citric acid, malic acid, etc., also start to accumulate at this time.


Arabica is a relatively broad name for coffee varietals and the Robusta varietal is often compared with it. Because of different genes, growth environment, etc., the organic acid, sugar, and other nutrients in the Robusta coffee beans are much lower than the Arabica, which makes it boring to drink.


Because of Arabica’s rich nutrients, it’s acid and sugar make it taste clean and smooth causing it to be favored by more people.


Common coffee processing methods can be roughly categorized as natural, honey, and washed. In conventional processing, the acidity of the washed coffee is brighter and easier to be perceived than other processed coffee.

(Washed processing)

(Washed processing)

On the other hand, because honey and natural coffee beans are dried with mucilage or pulp, there are more opportunities for microbial fermentation than washed coffee and different chemical compounds are being produced.

(Honey processing)

(Honey processing)

(Natural processing)

(Natural processing)

It will make people feel that the acidity is not very predominant but that the sweetness is stronger. Therefore, you can make your choice of taste preference based on different processing methods.


When roasting coffee the darker roast it is the higher the degree of caramelization will have, and the more the acid will be damaged.

For high-quality coffee green beans, light-to-medium roast is the right choice, exposing it’s rich flavors such as a floral and/or fruity fragrance.


This is also why specialty coffee roasters are leaning more towards roasting their coffee light, showing more of the charming characteristics of coffee.

Taste effect

Imagine if you are eating an apple, a pineapple, or a kiwi and you can only taste the sweetness from them. Would you still like them?


Would you feel like you are eating fake fruits? This is because the four tastes we often mention “sourness, sweetness, bitterness and saltiness” interact with each other. Sourness, sweetness and a little bit of saltiness will make the flavor taste three-dimensional.


Therefore, the acid in the coffee also has the same pleasant taste effect which can enhance the winey and fruity flavor in the coffee.

After the summary above, did you find that the "acid" in coffee is not so terrible?

The combination of high-quality acid and pleasant sweetness gives us an enjoyable experience like drinking fruit juice. Although it is a personal preference to choose to drink a cup of sour coffee, it is still such a regret if you miss something you might like because of some misunderstandings.

If you are interested in acidity, next time you go to a coffee shop let the barista recommend an excellent fruity type of coffee for you.


[Curiosity] Does the filter paper need to be soaked before brewing?

Do you really want to soak the filter paper before brewing after all?

Curious Saya has been plagued by differing opinions on this issue for quite some time. Though some have performed experiments and written articles, she has never done them herself and finally could not restrain herself.


So on a sunny and slightly muggy morning it seemed destined for taking care of things.

Saya got together with Dabai to conduct an experiment pitting traditional methods against uncommon ones.


We have heard positive and negative reasons for soaking the filter paper:


These reasons have been heard from the mouths of baristas who use different brewing techniques. We don’t know if these baristas have ever done these experiments, but they absolutely inspired us to do this experiment.


  • Experiment filter cups: hario V60 ceramic filter cup, kalita stainless steel cake cup, bonavita ceramic smart cup

  • Experimental filter paper: Mola, V60 bleached filter paper

  • Experiment brewer: SCI Brewing Instructor Dabai

  • Experiment coffee: Torch Mountain Man Coffee Beans

  • Participating Q-Graders: Internet Persona Joel, Roast Master Little Cabbage, and Curious Saya

  • Experiment objective: To compare the TDS, extraction rate, taste and texture of coffee brewed from soaked and non-soaked filter papers under the same conditions of filter cup brewing, water temperature and filter paper. 

Within this process, TDS will be measured by a measuring instrument, the extraction rate will be calculated by a formula, and the taste will be recorded by three Q-Graders. The table of their notes is below:


Instructor Dabai kept performing the test over and over, and our three Q-Graders kept on drinking.

They became a bit excited from all the drinking(I hope they didn’t drink too much…)


Now, to come back to the subject, the final results were quite interesting. 

First and foremost, a table of the combined three Q-Grader evaluations: 


We used these three filter cups to make coffee with soaked filter paper and non-soaked filter paper, respectively. When scoring, we looked at seven different details of the coffee, and summarized the following points:

1. Using non-soaked filter paper or soaked filter paper has little effect on the aromatic trend of the coffee, but there is a clear discrepancy in taste;

2. Coffee brewed without soaked filter paper is stiff, dry and tart, and coffee brewed with soaked filter paper is a distinctive and smooth;

3. When looking at the extraction rate, we can see that the extraction rate of soaked filter paper is marginally higher than that of non-soaked filter paper, though the difference is inconsequential.

-Further Discussion: To Soak with Cold or Hot Water -

After we answered the problem of whether to “soak or not soak the filter paper before brewing,” we discovered another problem: if you must first soak the filter paper, is it better to use cold or hot water?


Consequently, the three decided to seize the moment and simply perform this experiment as well.

We directly used V60 to do the test, brewing two cups of coffee. Before making each cup, we soaked the filter paper, once with hot water and the other with cold water. The data is as follows:



The sense of sweetness of the coffee made with filter paper soaked with cold water is slightly better.  The texture is thick but mixed, and after it cools, the flavor becomes bitter and astringent.

Of course, we believe that every instrument, every filter paper, and whether or not it is soaked are all ways of making coffee more spectacular. Some friends who like Japanese-style brewing will choose to not soak their paper. The results from this experiment are just a reference.

If you have interested friends, please feel free to conduct your own experiments, and we can communicate about our findings together.