What is steaming? What is the effect of the amount of steaming water on coffee extraction?

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01 | principle of steaming

Steaming is a very important step in the brewing process of hand-brewed coffee, which means the beginning of coffee extraction. Let's first take a look at the process of steaming coffee from a physical point of view. The microstructure of coffee powder is actually similar to that of a honeycomb, with numerous penetrating holes in which coffee beans continue to emit carbon dioxide and volatile aromatic substances that are initially stored in these holes.

When we extract with hot water, the hot water will first be heated and extracted along the periphery of the coffee powder. at this time, the carbon dioxide inside the powder is discharged along the hole, isolating the deep communication between the hot water and the coffee powder. as a result, the hot water cannot seep into the coffee powder. So the hot water will only wash the surface of the coffee powder and slip away along the gap between the coffee powder particles, resulting in that only the surface of the coffee powder is extracted, but not the interior. Some of the hot water flowed away without even participating in the extraction of coffee powder.

The main purpose of steaming in hand-brewed coffee is to help coffee powder discharge carbon dioxide smoothly and quickly, so as to improve the extraction efficiency of the following steps.

02 | method of steaming

After understanding the principle of steaming, what should be paid attention to when steaming?

Water quantity: usually the proportion we take is that the amount of water is about twice the weight of powder. It is usually just enough to soak the coffee powder completely.

Time: the steaming time is about 20-30 seconds after water injection, which is related to the freshness and baking degree. The fresher the beans are, the longer the steaming time is, the deeper the beans are, the more intense the exhaust is, so the steaming time is relatively long.

Technique: many people have their own opinions and opinions, depending on their personal preferences.

Personal understanding of steaming:

Be gentle, soak quickly and evenly, and control as little water as possible. Tenderness is to prolong the immersion and extraction time of water in coffee powder as much as possible. Fast is to make the soaking time of all coffee powder consistent as far as possible. The reason for controlling the small amount of water is that the hot water injected during steaming is not too much involved in the extraction of coffee substances, and too much water will affect the extraction efficiency of the following steps.

03 | verify the effect of steaming water on the extraction of filtered coffee

The purpose of this experiment is to explore the effect of stuffy steam on filtered hand flushing.

The experimental apparatus uses a smart cup, the hand steaming stage to open the piston, simulated filter cup extraction, the latter part of the piston closed, the use of immersion extraction to prevent experimental errors caused by water injection.

Group 1 (36 g of steaming water):

Setting of cooking parameters:

Experimental coffee beans: sun Sidharma Lion King (baking date 5.19)

Cooking method: hand flushing

Degree of grinding: 4W (BG)

Smart cup, 18 grams of powder, water temperature 90 degrees, ratio of water to powder close to 1:15

38 grams of water steaming for 20s (open the piston)

After injecting water into 240ml (closing piston), the total water volume is 278g, and the soaking time is 2 minutes and 30s.

Flavor description:

The entrance has sticky tropical fruit and berry flavor, high cleanliness, orange peel at the end, long finish and rich fluctuation.

Sweetness: ☆☆☆☆

Acidity: ☆☆

Bitterness: ☆

Alcohol thickness: ☆☆☆☆

Group 2 (75 g of steaming water):

Setting of cooking parameters:

Experimental coffee beans: sun Sidharma Lion King (baking date 5.19)

Cooking method: hand flushing

Degree of grinding: 4W (BG)

Smart cup, 18 grams of powder, water temperature 90 degrees, ratio of water to powder close to 1:15

75 grams of water steaming for 20s (open the piston)

After injecting water to 200ml (close the piston), the total water volume is 275g and the soaking time is 2 minutes and 30s.

Flavor description:

The entrance feels the obvious orange acid feeling, the mellow thickness is general, the taste is slightly tea, the flavor is single and has no layered feeling.

Sweetness: ☆☆

Acidity: ☆☆☆

Bitterness: ☆

Alcohol thickness: ☆☆

Contrastive conclusion:

If there is too much steaming water, the hot water in the steaming part of the front section will not extract enough coffee ingredients, but dilute the whole cup of coffee, affecting the overall alcohol thickness, layering and final flavor performance of the coffee.

04 | end

As the saying goes, "A good beginning is half done". For hand-brewed coffee, the steaming process is very important. Although it is only a small part of the hand-brewing process, it has a significant impact on the flavor of the final cup of coffee. To brew a good cup of coffee, we also need to take every step seriously and understand how each step affects the taste of the coffee.