Coffee is a Science: The Complete Guide to Coffee Analysis, Compounds, and Evaluation

Exploring the physical characteristics, chemical compounds, and sensory evaluation of coffee

Sep 15, 2025

Introduction: Coffee as a Scientific Endeavor

Welcome to the fifth installment of our "Coffee Is" series, where we delve into coffee through multifaceted perspectives. In this chapter, we explore coffee is a science - a systematic pursuit of knowledge about the physical attributes, chemical composition, and sensory evaluation that define exceptional coffee quality.

From green coffee analysis to the intricate world of cupping coffee, understanding the science behind coffee compounds and flavor perception transforms how we appreciate and evaluate this remarkable beverage. Every sip represents the culmination of scientific principles applied throughout the supply chain.

For how these compounds interact with processing styles, see Coffee is a Process and the practical Washed vs Natural comparison both are useful when mapping chemistry to cup.

The Science of Green Coffee Evaluation

Green coffee analysis begins with systematic evaluation of physical characteristics that influence roasting and final flavor. This coffee science approach ensures consistency and quality in specialty coffee production.

Physical Characteristics of Green Beans

Green coffee grading evaluates several key physical attributes using standardized methods:

• Screen Size: Measuring bean size through mesh screens, typically ranging from 14-19 64th inch increments
• Density: Assessing cellular structure through bulk density or liquid displacement methods
• Moisture Content: Maintaining optimal 9-12% moisture for quality preservation and microbial stability
• Defect Analysis: Identifying physical imperfections that impact coffee evaluation

These physical characteristics directly influence roasting profiles and help predict potential flavor outcomes in coffee compounds analysis.

Defect Classification in Specialty Coffee

Specialty coffee standards require zero Category 1 defects and fewer than 5 Category 2 defects per 350g sample:

• Category 1: Full blacks, full sours, severe insect damage, foreign matter
• Category 2: Partial defects, immature beans, parchment, floaters, withered beans

Understanding these defects is crucial for green coffee analysis and maintaining specialty grade quality standards.

Chemical Compounds in Green Coffee

The science of coffee compounds reveals a complex biochemical profile that transforms during roasting. Green coffee contains various compound categories that contribute to flavor development.

What makes Ethiopian coffee particularly fascinating from a chemical perspective is its genetic diversity. The 10,000+ heirloom varieties in Ethiopia's highlands each express slightly different compound profiles - different ratios of sugars, acids, and aroma precursors. This is why a Yirgacheffe tastes different from a Guji, even when processed identically. The plant's genetics determine the chemical raw materials; processing and roasting transform them.

Organic Acids and Flavor Foundation

Organic acids make up approximately 5% of green coffee by weight and provide the foundation for acidity and tartness:

• Simple Organic Acids: Citric, malic, acetic, and quinic acids that survive roasting
• Chlorogenic Acids: Complex acid chains that break down into various flavor compounds during roasting

These coffee compounds are highly extractable and contribute significantly to the perceived brightness and complexity in coffee flavor.

Practical Example: Mapping Compounds to Tasting Notes

Want a quick mental model? Use this mapping when cupping or sourcing:

• Citric & malic acids: Bright, citrus and apple-like acidity
• Sucrose breakdown: Sweetness and caramel notes after roasting
• Chlorogenic acid derivatives: Bitterness and body components when over-extracted
• Volatile esters and aldehydes: Fruity and floral aromatics often associated with naturals

Lab & Field Tools for Green Coffee Analysis

Useful tools include moisture meters (for immediate QC), bulk density kits (predict roast behavior), and spectrophotometry/HPLC for deep chemistry when available. Even simple, repeatable cupping protocols provide high-value information for buying decisions.

If you source, pair lab checks with our sourcing guide and our regional origin map Practical Guide to Ethiopian Green Coffee Origins.

Minerals, Sugars, and Bitter Components

Additional compound categories include:

• Minerals and Salts: Potassium, magnesium, calcium providing subtle saltiness (1% by weight)
• Sugars: Sucrose (8-12% by weight) that caramelizes and contributes sweetness
• Bitter Compounds: Caffeine, trigonelline, and chlorogenic acids creating complexity

These elements interact during roasting to develop the balanced flavor profile characteristic of quality coffee.

Aroma Precursors and Textural Elements

Volatile compounds and structural components complete the green coffee composition:

• Aroma Precursors: Aldehydes, ketones, furans, pyrazines forming the basis of coffee flavor notes
• Lipids and Amino Acids: Providing body, texture, and nutty characteristics
• Structural Components: Cellulose, hemicellulose, lignin maintaining bean integrity

These compounds transform dramatically during roasting, creating the thousands of aroma compounds that define coffee science.

Flavor Perception and Sensory Science

Coffee flavor perception involves complex interactions between chemical compounds and human sensory systems. Understanding this science enhances coffee evaluation techniques.

The Components of Flavor

Flavor in coffee comprises three primary elements:

• Taste: Chemical detection of sweet, sour, salty, bitter, umami on the tongue
• Aroma: Olfactory perception through the nose, the dominant contributor to flavor
• Body/Texture: Tactile sensation of weight, viscosity, and mouthfeel

Aroma, processed through olfactory neurons and the brain's limbic system, provides the majority of flavor complexity in coffee evaluation.

Sensory Errors and Bias in Tasting

Scientific sensory analysis identifies common errors that affect coffee flavor perception:

• Adaptation: Reduced sensitivity after repeated exposure to intense flavors
• Contrast Effects: Perception changes based on preceding samples
• Expectation Bias: Preconceived notions influencing flavor interpretation
• Context Effects: Environmental factors impacting sensory experience

Recognizing these physiological and psychological factors improves the accuracy of coffee evaluation methods.

Cupping Coffee: The Art of Sensory Evaluation

Cupping represents the systematic sensory evaluation of coffee, combining scientific methodology with skilled assessment. This coffee science approach standardizes flavor analysis across the industry.

The Cupping Protocol

Professional cupping follows established procedures:

• Sample Preparation: Light roasting, grinding, and brewing with consistent ratios
• Evaluation Framework: Assessing fragrance, aroma, flavor, aftertaste, acidity, body, balance, sweetness, uniformity, clean cup, overall
• Scoring System: Numerical ratings from 1-10 across quality attributes

Modern cupping incorporates new forms like the Coffee Value Assessment (CVA) that separate descriptive and scoring functions.

Best Practices for Accurate Evaluation

Scientific cupping methodology includes:

• Blind Tasting: Randomized sample presentation to minimize bias
• Reference Standards: Using baseline coffees for calibration
• Replication: Multiple evaluations for statistical reliability
• Controlled Environment: Consistent conditions for valid comparisons

These practices ensure objective coffee evaluation that supports quality assessment and pricing decisions.

Conclusion: The Scientific Foundation of Coffee Excellence

Quick Lab Protocol (Moisture & Density)

A repeatable, low-cost protocol for quick green QC:

1. Collect a 350g representative sample from multiple bags.
2. Measure moisture with a calibrated moisture meter (record three readings, average).
3. Measure bulk density using a standardized cylinder or displacement kit.
4. Record screen size distribution and note any visible defects.
5. Roast a small 50–100g sample using your sample roaster and cup for initial acceptance.

Mini Glossary

• Screen Size: Mesh measurement for bean size (64th inch units)
• Bulk Density: Predictive of roast behavior and end yield
• Cupping: Standardized sensory evaluation method for coffee

Coffee is a science that demands systematic knowledge of physical characteristics, chemical compounds, and sensory evaluation. Understanding green coffee analysis, flavor perception, and cupping methodology provides the foundation for appreciating and producing exceptional coffee.

At Ethio Coffee, we apply rigorous scientific principles to every aspect of our sourcing and evaluation process, ensuring that our partners receive coffee of the highest quality and consistency.

Continue Your Coffee Education

Now that you understand the science behind coffee quality, explore how that knowledge is applied:

• Coffee Is Art - How roasters use scientific understanding to craft exceptional roast profiles
• Sourcing Green Coffee - Apply quality evaluation to your buying decisions
• 2026 Specialty Coffee Trends - See how science is driving innovation in the industry