The Impact of Grinder Speed on Coffee's Sweetness and Acidity

JC咖啡小學堂

2025-01-24

磨豆機轉速對咖啡甜感與酸感的影響

Contents:

1. Grinder Speed and Fine Particle Production
2. Heat Impact on Aromatic Compounds
3. Extraction Uniformity and Flavor Balance
4.Sensory Preferences and Personal Perception
5. Example Analysis: Ethiopia Geisha Village Banjii Green Label Washed

Coffee flavor is influenced by various factors, and one important variable is the grinder speed (RPM). Different speeds affect the heat generated during grinding, particle uniformity, and the amount of fines, which in turn alters the extraction process and the final flavor. This article explores the differences between high-speed (1500 RPM) and low-speed (500 RPM) grinding, analyzing why low-speed grinding might enhance sweetness.

Grinder Speed and Fine Particle Production

The grinder speed directly impacts the particle distribution and the production of fines, the smallest particles in the grind. Fines can lead to over-extraction during brewing, bringing out bitterness and off-flavors.

Low Speed (500 RPM): Low-speed grinding is gentler, producing fewer fines. The resulting grind is more uniform, leading to more stable extractions and a natural balance between sweetness and acidity.

High Speed (1500 RPM): Higher speeds generate more friction, producing more fines. These fines can cause over-extraction, masking the coffee's natural sweetness and introducing undesirable bitterness.

The creation of fines is a key factor in the expression of sweetness and acidity. The uniformity of low-speed grinding helps preserve the coffee's natural sweetness, avoiding imbalances from over-extraction.

Below is a particle size distribution measured by the CM-200 grinder. It is clear that low speed (500 RPM) has a more concentrated distribution (left), while high speed (1500 RPM) results in a broader distribution (right).

CM-200量測粒徑分佈

Heat Impact on Aromatic Compounds

The heat generated during grinding can affect the aromatic compounds in the coffee beans, especially the volatile compounds related to sweetness and acidity. Higher speeds generate more heat, which may cause some aromatic compounds to evaporate prematurely, altering the coffee's flavor.

Low Speed (500 RPM): Lower speed produces less heat, preserving the volatile aromatic compounds in the beans. Compounds related to sweetness, such as sugar breakdown products and floral or fruity aromas, are retained more fully.

High Speed (1500 RPM): High speed generates more heat, which may evaporate some of the aromatic compounds related to acidity, weakening the acidic notes and creating a thicker, less refreshing sweetness.

Low-speed grinding preserves the natural flavors of the beans, especially delicate floral and fruity notes, due to lower heat generation.

Extraction Uniformity and Flavor Balance

The balance between sweetness and acidity is strongly influenced by extraction uniformity. Low and high speeds affect the extraction differently, leading to distinct flavor profiles.

Low Speed (500 RPM): The higher particle uniformity allows for more stable extractions. The levels of acidity and sweetness are clearly defined, with a light, natural sweetness.

High Speed (1500 RPM): The slightly uneven particle distribution can lead to over-extraction in some areas, masking sweetness or dulling the acidity. The sweetness may become heavier but lacks finesse.

When extraction is uniform, sweetness and acidity can coexist harmoniously. Low-speed grinding contributes to this balance.

Sensory Preferences and Personal Perception

Each person has different sensitivity to taste and preferences, which also influences their perception of grinder speed. Coffee ground at low speed, with its balanced sweetness and acidity, is often perceived as sweeter.

Low Speed (500 RPM): Acidity is bright and clean, and the sweetness is more noticeable. The flavor profile is clear and structured, particularly suitable for coffees with floral or fruity aromas.

High Speed (1500 RPM): The acidity may become muted or less distinct, while the sweetness becomes heavier but lacks complexity. This is more suited for those who prefer a bolder, richer taste or use methods like espresso that emphasize stronger flavors.

Example Analysis: Ethiopia Geisha Village Banjii Green Label Washed

Using a light roast coffee bean as an example: Ethiopia Geisha Village Banjii Green Label Washed, with flavors like jasmine, honey, lime, fruit juice and clean, the results at different speeds may be as follows:

Low Speed (500 RPM):

Floral Notes: The jasmine aroma is more pronounced, with strong structures and a long-lasting finish.

Acidity: Lime acidity is bright and delicate, with a refreshing fruit juice quality.

Sweetness: Honey sweetness is natural and crisp, with a clean aftertaste.

Overall Performance: The flavor is rich with structures, balanced acidity and sweetness, and a pure flavor profile.

High Speed (1500 RPM):

Floral Notes: The jasmine aroma is slightly weaker compared to low speed, with sweetness slightly masking the floral notes.

Acidity: Lime acidity becomes fuller, but with reduced structures.

Sweetness: Honey sweetness becomes richer, but might feel too heavy.

Overall Performance: The flavor leans towards being richer but lacks the delicacy and refreshing aftertaste of low-speed grinding.

In coffee grinding, both low-speed (500 RPM) and high-speed (1500 RPM) have their characteristics. However, when it comes to sweetness and acidity, low-speed grinding is more suitable for those seeking a refined and balanced flavor profile. Low speed reduces the production of fines and heat generation, helping preserve the coffee's natural aromatic compounds, and enhances sweetness and delicacy. Additionally, the uniform particle distribution aids in stable extraction, allowing for perfect balance between acidity and sweetness.

Justin Coffee stores use Mahlkönig EK OMNIA grinders, which can adjust speeds between 500 RPM and 1500 RPM to meet the grinding needs for different scenarios. Whether for the delicate flavor of pour-over coffee or the boldness of espresso, the grinder can be precisely adapted.

If your goal is to highlight floral, fruity, and bright acidic notes with a light sweetness, low-speed grinding is the ideal choice. High-speed grinding, however, is more suitable for scenarios where quick grinding or a richer taste is desired. Adjusting the speed based on the coffee bean's characteristics and personal preferences will help you achieve the best coffee flavor experience.

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