The flavor of coffee is influenced by multiple factors such as grinding degree, extraction efficiency, and powder distribution, and the grinder is the core tool for adjusting these parameters. The following analysis is conducted from dimensions such as scientific principles, operation methods, and flavor correlations to help users precisely control the flavor of coffee.
First, the correlation between grinding degree and flavor
The influence of grinding degree on extraction
Fine grinding (such as Italian concentration grade) :
The particles have a large surface area, a fast extraction speed, and are prone to releasing more soluble substances (such as caffeine, acids, and caramelized substances).
Flavor characteristics: High body, strong bitterness, low acidity, suitable for espresso or short extraction methods.
Medium grinding (such as hand-brewed coffee grade) :
The extraction is balanced, and the acidity, sweetness and bitterness are well-coordinated.
Flavor characteristics: Balanced sweet and sour taste, soft texture, suitable for most brewing methods (such as V60, Chemex).
Rough grinding (such as French press grade) :
The particle surface area is small, the extraction speed is slow, and it is easy to retain highly volatile aromatic substances (such as floral and fruity scents).
Flavor characteristics: High acidity, low bitterness, prominent aroma, suitable for steeping brewing.
Mathematical model for flavor adjustment
Extraction rate (EY) and concentration (TDS) :
The finer the grinding, the higher the EY and TDS, and the stronger the flavor. On the contrary, it is even milder.
Target value reference:
Espresso: EY 18%-22%, TDS 8%-12%;
Hand-brewed coffee: EY 18%-20%, TDS 1.2%-1.5%.
Second, the specific methods for adjusting the flavor through a grinding machine
Select the type of cutter head
Flat Burr
The grinding particles are uniform but contain a lot of fine powder, making it suitable for users who pursue a rich flavor (Ruyi concentrated).
Conical Burr
The fine powder content is low, and the flavor layers are more distinct. It is suitable for hand brewing or cold brewing.
Ghost Burr
The particles have regular shapes and a prominent sweet taste, but the price is relatively high.
Adjust the grinding degree
Espresso
Target grinding degree: Similar to salt particles (about 200-300μm).
Adjust the direction: If the bitterness is too strong, you can slightly adjust the coarseness (increase the extraction time compensation). If the sourness is prominent, refine it.
Hand-brewed coffee
Target grinding degree: Similar to coarse granulated sugar (about 600-800μm).
Adjust the direction: If the texture is thin, grind it finely. If the bitterness is strong, thicken it.
French press kettle
Target grinding degree: Similar to sea salt particles (approximately 800-1000μm).
Adjust the direction: If the acidity is too high, grind it finely. If the turbidity is strong, thicken it.
Control the rate of fine powder
The influence of fine powder:
Fine powder will accelerate the extraction, resulting in an enhanced bitterness and astringency.
Adjustment method:
Use a sieve to remove the excess fine powder (such as filtering through an 80-mesh sieve);
Choose a cutter head with a low fine powder content (such as a conical knife or a ghost tooth).
Combine the optimization of brewing parameters
Powder to water ratio
When fine grinding, reduce the ratio of powder to water (such as 1:1.5) to avoid excessive extraction.
When performing coarse grinding, increase the ratio of powder to water (such as 1:18) to enhance the flavor richness.
Water temperature:
Fine grinding combined with low temperature (such as 88-90℃) reduces bitterness.
Coarse grinding combined with high temperature (such as 92-94℃) enhances the extraction efficiency.
Third, cases of grinding adjustment under different brewing methods
Espresso
Problem: The extraction time is too long (>30 seconds), resulting in a bitter taste.
Adjustment:
Coarser the grinding degree (for example, from #6 to #7, taking EK43 as an example);
Reduce the amount of powder (for example, from 18g to 17g) and lower the extraction pressure.
Hand-brewed coffee
The taste is thin and lacks layers.
Adjustment:
Fine-tune the grinding degree (for example, from #20 to #18, taking the C40 hand-craned mill as an example);
Extend the water injection time (for example, from 2 minutes and 30 seconds to 3 minutes).
French press coffee
The acidity is too high and the flavor is sharp.
Adjustment:
Refine the grinding degree (such as from #10 to #8);
Extend the soaking time (for example, from 4 minutes to 5 minutes).
Fourth, advanced techniques and precautions
Calibrate the grinding machine regularly
Wear of the cutter head can lead to a coarser grinding degree and requires calibration every 3 to 6 months (if using calibration screws or a laser particle size analyzer).
Avoid overheating of the grinding machine
Continuous grinding can cause the cutter head to heat up, affecting the flavor (such as acid loss). Suggestion:
The single grinding amount shall not exceed 50g.
Grinding machines using low-speed motors (such as DC brushless motors).
Adjust in combination with the characteristics of coffee beans
Light-roasted beans: The grinding degree needs to be adjusted to increase the extraction rate (for example, from medium grinding to fine grinding).
Deep-roasted beans: The degree of coarser grinding should be adjusted to avoid bitterness (for example, coarse grinding should be adjusted to medium-coarse grinding).
Fifth, Summary
The core of adjusting the flavor of coffee through a grinder lies in precisely controlling the grinding degree, fine powder rate and extraction parameters. Users need to flexibly adjust the type of cutter head, grinding fineness and brewing parameters according to the brewing method, the characteristics of coffee beans and their personal taste preferences. For example:
When pursuing a rich flavor, choose a flat knife, fine grinding and high-temperature extraction.
When pursuing a refreshing and acidic taste, choose a conical knife + coarse grinding + low-temperature extraction.
Suggestion:
Regularly test the grinding consistency using a screen or a laser particle size analyzer;
Record the flavor changes after each adjustment and establish a personal parameter library;
Give priority to choosing grinding machines with fine-tuning functions (such as EK43, Comandante C40).
Through scientific adjustment, users can fully exploit the potential of the grinder and achieve precise control of coffee flavor.