What is Extraction?

In simple terms, extraction refers to the process of dissolving flavor compounds and aromatic substances from ground coffee beans into water. When brewing coffee, hundreds of compounds are extracted into the water, directly affecting the final taste and aroma of the coffee. Common substances extracted include, but are not limited to:

• Caffeine
• Acids
• Oils
• Sugars
• Carbohydrates

How Extraction Influences Taste

Coffee compounds do not extract simultaneously or at the same rate:

• Early-stage extraction: Fruit flavors and acidity.
• Mid-stage extraction: Sweetness and balance.
• Late-stage extraction: Bitterness.

Under-extracted coffee lacks sweetness and complexity, often tasting overly sour or sharp.
Over-extracted coffee becomes excessively bitter, masking sweetness and pleasant acidity.
Proper extraction strikes a balance, producing coffee with harmonious flavors.

What is the Perfect Extraction?

You may have heard of Extraction Yield or measuring Total Dissolved Solids (TDS). Simply put, this represents how many compounds are extracted from coffee into the water, typically between 18% to 22%.

However, rather than pursuing a specific numerical target, focus on extracting delicious compounds that highlight the coffee's unique flavors.

How to Control Extraction

To achieve the best flavors, controlling extraction is crucial. If your coffee doesn’t taste right, understanding extraction control can solve the issue:

• Coffee too sour? Likely under-extracted.
  Solution: Brew longer or grind finer.
• Coffee too bitter? Likely over-extracted.
  Solution: Grind coarser or shorten brewing time.

Adjustments to extraction also compensate for bean freshness:

• Older coffee beans: Grind finer to enhance extraction and intensify flavor.
• Dark roast beans: Easier to extract due to a more porous bean structure. Grind slightly coarser compared to lighter roasts to prevent over-extraction.

Factors Affecting Extraction

Extraction is influenced by multiple factors aside from the inherent characteristics of coffee beans. These controllable variables include grind size, water temperature, and brewing method.

Factor 1: Grind Size

• Finer Grind:
• Increases extraction speed due to greater surface area.
• May cause bitter flavors due to rapid extraction of many compounds.
• Reduces gaps, slowing water flow and prolonging brewing time (for drip methods).
• Coarser Grind:
• May produce weak, underwhelming coffee due to insufficient extraction.

Tip: When brewing with fine grounds, pay attention to water flow to avoid uneven extraction. Small particles may rise, becoming isolated and under-extracted.

Factor 2: Brewing Time

Longer brewing leads to higher extraction:

• Short brewing generally produces brighter acidity.
• Extended brewing may increase bitterness.

Examples:

• Espresso: Short brewing time (25-30 seconds), fine grind, high pressure.
• French Press: Coarser grind, longer brewing time (4 minutes), minimizes bitterness.

Factor 3: Water Temperature and Quality

Ideal brewing temperature: around 90°C (194°F to 205°F).

• Higher temperatures accelerate extraction.
• Lower temperatures slow extraction, unable to extract certain compounds (notably in cold brew, which is smoother and less acidic).

Water quality recommendations:

• Neutral pH (7.0), free from contaminants that affect flavor.
• Moderate mineral content:
• Magnesium (Mg²⁺) highlights fruity, intense flavors.
• Calcium (Ca²⁺) increases body and mouthfeel.
• Excessive minerals reduce extraction efficiency, negatively affecting flavor.

Factor 4: Coffee Bed Distribution

Consistent and even coffee bed distribution is essential for uniform extraction:

• Uneven coffee beds or water flow cause channeling, where water bypasses certain areas, leading to uneven extraction.
• Poor pouring techniques may push grounds against filter walls, causing extraction inconsistencies.

Important considerations:

• Too shallow coffee bed: Rapid water flow leading to under-extraction.
• Too deep coffee bed: Excessive brewing time resulting in over-extraction.

Conclusion

Extraction involves managing multiple variables simultaneously. Understanding and controlling these factors allows precise tuning of coffee flavors, enabling you to discover and enjoy coffee’s full potential.