影響咖啡風味的「通道效應」 What causes the channeling effect?
The process of pour over brewing coffee creates a “channeling effect” that can cause the uneven extraction. This results in a mix of under- and over-extracted flavors or textures in the coffee.
What is the channeling effect? According to the physical characteristics of water taking an easy path (where the resistance is low), if a “channel” is created in the coffee powder, the water will preferentially choose such a channel to flow, which will make the coffee near the channel more extracted. The flow rate of other parts is too low or there is no water flow at all, resulting in insufficient extraction and uneven coffee extraction, which is the so-called “channeling effect.”
What causes the channeling effect?
The powder is uneven or too tight
Pouring coffee powder is a detail that is easily overlooked by many people, but it also has an important impact on the success of subsequent extraction. When the coffee powder is poured into the filter cup, the powder can be evenly distributed into small hills. There is no need to make a flat action. After beating, it is easy to make the gap between the powder and the powder smaller and firmer, and it is easy to block the subsequent steaming. The required water flow to wet the space cannot achieve the goal of infiltrating the coffee powder at the same time.
Coffee powder is not evenly moist
Dry coffee powder will repel water more than soaked coffee powder, which is related to the mutual combination of water molecules. Dry coffee powder has lower hydrophilicity. Therefore, if blooming at the beginning of brewing is more successful, the coffee grounds are fully soaked, ideal for even extraction.
During the brewing process, gently pour water in a circle to help the water flow stably and evenly wet the coffee powder.
The strong exhaust carbon dioxide in the coffee beans prevents the contact between water and coffee powder
The fresh beans or the heavier roasted coffee beans, the more vigorous the carbon dioxide exhaust, the carbon dioxide will block the contact between the coffee powder and the water, resulting in uneven extraction. Therefore, through blooming the coffee powder is fully infiltrated and water is poured evenly and gas is discharged, which helps to dissolve the aroma substances of coffee more completely in the follow-up.
The water is poured to the junction edge of the filter paper and the coffee
If the water is poured to the edge, the water will directly pass through the filter paper and flow into the sharing pot without passing through the coffee grounds.
Did you find that the brewing details we usually do are to avoid the channelinf effect? Follow us to understand the working principle of extraction step by step. The more familiar you are, the better it will help you to brew good coffee. With a solid basic concept, you can brew the coffee with the right taste by adjusting the factors.
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