Why Does Moka Pot Coffee Taste Burnt? How to Adjust Over-Extracted Moka Pot Coffee? What to Do When Moka Pot Coffee is Scorched? Why Does Moka Pot Coffee Easily Over-Extract?

FrontStreet Coffee has discovered that many friends are troubled by the issue of over-extraction in moka pot coffee. Whenever FrontStreet Coffee shares posts related to moka pots, friends leave comments in the section asking questions like: "How can I avoid over-extraction in moka pot coffee?" or "Why does the extracted coffee taste so bitter?"

Indeed, compared to most other coffee brewing methods, moka pots are indeed more prone to over-extraction. Like espresso machines, they use pressurized extraction. The advantage of pressurized extraction is its high efficiency, allowing coffee to be extracted in a very short time. However, due to this high efficiency, coffee is also more likely to be over-extracted. Over-extracted coffee tastes noticeably burnt or has many off-flavors, and even with added sugar and milk, the coffee remains unpleasant to drink.

Solving Moka Pot Over-Extraction

So today, FrontStreet Coffee will share how we can solve the problem of over-extraction in moka pot coffee! By preventing bad flavors from appearing at the source, coffee can become much more enjoyable.

But before that, FrontStreet Coffee recommends that friends who don't fully understand the meaning of "over-extraction" first learn about it through the article "What is Over-Extraction." As the saying goes, "Know your enemy and know yourself, and you will never be defeated." Only after becoming familiar with the concept of over-extraction can we more thoroughly improve the problem of over-extracted coffee.

Channel Effect

For pressurized extraction, one of the reasons leading to frequent over-extraction in coffee is the "channel effect." What is the channel effect? It refers to hot water concentrating in a specific area for extraction, causing the coffee grounds in that area to be over-extracted while the coffee grounds in other areas are under-extracted. The resulting coffee tastes both bitter and sour, with very poor balance.

The reason channel effects occur is because water has inertia and will preferentially flow to places where it can move easily. To dissolve a large amount of flavor compounds from coffee grounds in a short time, pressurized extraction typically uses very finely ground coffee. This allows the coffee puck to have enough resistance to build pressure. However, if a certain area has less coffee grounds with lower density than other areas, hot water will concentrate and pass through this spot, leading to the channel effect. Therefore, if we want to improve the over-extraction problem in moka pot coffee, we must first prevent the occurrence of channel effects. So, what factors can lead to channel effects?

1. Uneven Distribution

Similar to espresso, uneven distribution of coffee grounds can cause channel effects. If the coffee grounds in the filter basket are distributed unevenly and tamping is done without adjustment, density differences will appear in the coffee puck, and channel effects will follow.

This situation is easy to solve! After putting the grounds into the filter basket, we can pay appropriate attention to see if the amount of coffee grounds is similar in every area. If so, we can proceed with tamping and extraction. If not (as shown in the picture above), we need to use our fingers to stir the coffee grounds to make their distribution uniform. Then gently tap the filter basket to make the connections between coffee grounds tighter, and finally proceed with tamping and extraction.

By adjusting the coffee grounds in this way, we can make the density of the coffee puck tend toward consistency, making it more difficult for channel effects to occur.

2. Low Heat and Cold Water

Initial water temperature and heat level both affect the extraction of moka pot coffee. They mainly influence the time from heating the moka pot to coffee flowing out. The longer the heating time, the more likely channel effects will occur during the extraction process.

As we all know, moka pots need to be heated to generate sufficient steam pressure, which pushes hot water to extract the coffee grounds. During the heating process, steam is continuously generated, and steam from the water in the lower chamber rises upward, moistening the coffee grounds at the bottom of the puck. The areas pre-moistened by steam will have reduced density, making them easier to pass through during extraction compared to other areas. The longer the heating time, the more the puck gets moistened, the lower its density, and the easier it is to pass through.

In other words, when the heating time is too long, the density of the coffee puck changes due to steam, making channel effects more likely to occur during extraction. Using too low heat during brewing and low initial water temperature (the temperature of water initially poured into the lower chamber) will both extend the heating time, making extraction more unstable. Therefore, when conditions permit, FrontStreet Coffee recommends using medium to high heat to brew moka pot coffee before coffee flows out, and the higher the initial water temperature, the better. This can significantly reduce the occurrence of channel effects and increase the probability of making delicious coffee.

Heat Control After Coffee Flow

It's worth noting that after coffee starts flowing, it's best to adjust the heat for brewing the moka pot to low heat or even turn it off, using residual heat to generate steam to extract the moka pot coffee.

Because if you continue to use the current heat to extract coffee after it starts flowing, the excess steam will cause over-pressurization, making hot water pass through the coffee puck quickly in a short time, greatly shortening the extraction time. Besides under-extraction, continuous high-heat brewing will also lead to channel effects, making the coffee taste both bitter and sour.

Grind Size and Water Amount

Moka pots usually come with an instruction manual that details usage methods and official recommended parameters. For example, for a 2-cup serving, use a certain amount of coffee grounds and 120ml of water for brewing; for a 4-cup serving, use a certain amount of coffee grounds and 180ml. Many friends follow these parameters when first starting out.

There's nothing wrong with this, but if your grind is very fine, similar to espresso machine grind with flour-like particles, you need to pay attention to the amount of water used. Finely ground coffee more easily releases flavor compounds, and more water will increase the dissolved flavor compounds. If we use flour-like grind particles and also use a large amount of water, it will be very easy to brew a cup of moka pot coffee that is burnt, bitter, and rich in off-flavors.

Many friends use pre-ground coffee that cannot be freely adjusted in grind size. In this case, we need to control the coffee extraction rate by adjusting the amount of water and the heat level after coffee starts flowing. However, the latter is relatively difficult to adjust, so FrontStreet Coffee more recommends adjusting by reducing the amount of water.

The above are the three main reasons that FrontStreet Coffee can think of that lead to over-extraction in moka pot coffee. If friends have other discoveries, welcome to supplement them in the comments section~

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