Green Coffee Quality Control: Defects, Grading Systems & What Importers Should Inspect

A practical guide to evaluating green coffee quality before you buy

Dec 01, 2025

Introduction: Why Quality Control Matters

For importers and roasters, understanding green coffee quality control isn't optional it's fundamental to your business. A single defective lot can damage customer relationships, waste roasting capacity, and erode margins. Conversely, developing strong QC skills helps you identify exceptional value, negotiate fair prices, and build confidence in your sourcing decisions.

This guide covers the essential elements of green coffee quality control: defect identification, grading systems (with a focus on Ethiopian standards), physical measurements, and practical inspection protocols. Whether you're evaluating samples from a new supplier or conducting pre-shipment inspection, these fundamentals will serve you well.

Quality control connects directly to everything else in the supply chain from the agricultural practices that produce coffee to the processing methods that prepare it for export. Understanding QC helps you appreciate what's happening at origin and communicate more effectively with your Ethiopian coffee suppliers.

Understanding Coffee Defects

Coffee defects are imperfections in green beans that can negatively affect cup quality, roast consistency, or shelf life. The Specialty Coffee Association (SCA) and various origin-country grading systems categorize defects by severity and impact.

Category 1 Defects (Primary/Full Defects)

These are severe defects that significantly impact cup quality. A single Category 1 defect can ruin an entire cup. In SCA specialty grading, zero Category 1 defects are allowed in a 350g sample.

Category 2 Defects (Secondary Defects)

These defects have less severe but still measurable impact on cup quality. SCA allows a maximum of five Category 2 defects in a 350g specialty-grade sample.

Ethiopian Coffee Grading System

Ethiopia uses its own grading system that differs from the SCA framework, though both assess defect count and cup quality. Understanding Ethiopian grades is essential when sourcing from the current harvest.

Ethiopian Grade Classifications

Washed vs. Natural Grade Expectations

It's important to understand that washed and natural processed coffees often have different defect profiles:

• Washed coffees typically have more uniform appearance and fewer fermentation-related defects, making G1 more achievable
• Natural processed coffees may show more variation in color and occasional fruit remnants; G1 naturals command significant premiums
• Regional variations: Yirgacheffe washed G1 vs. Sidamo natural G1 will look quite different

Physical Quality Measurements

Beyond defect counts, several physical measurements help assess green coffee quality:

Moisture Content

Moisture content is critical for storage stability and roast consistency. The science of coffee preservation starts here.

Water Activity (aw)

Water activity measures the "free" water available for microbial growth and chemical reactions. It's increasingly used alongside moisture content for quality assessment.

• Target range: 0.50-0.60 aw
• Above 0.70 aw: Significant mold risk
• Below 0.45 aw: May indicate over-drying

Screen Size

Screen size indicates bean size and can affect roast uniformity. Ethiopian coffees are graded by screen size as part of quality assessment.

Note: Ethiopian heirloom varieties naturally produce smaller beans than many other origins. A screen 15 Ethiopian may cup better than a screen 18 from elsewhere. Understanding coffee varieties helps contextualize screen size expectations.

Density

Bean density correlates with altitude, ripeness, and potential cup quality. Higher-density beans typically come from higher altitudes and develop more complex flavor compounds.

• High density: >680 g/L - typically high-altitude, specialty grade
• Medium density: 620-680 g/L - standard quality range
• Low density: <620 g/L - lower altitude or quality issues

Sensory Evaluation: The Cup Test

Physical inspection tells part of the story, but sensory evaluation through cupping reveals how the coffee actually tastes. The SCA cupping protocol is the industry standard.

SCA Cupping Basics

• Sample prep: Light roast (Agtron 58-63), 8.25g coffee to 150ml water
• Water: 200°F (93°C), clean, neutral (125-175 ppm TDS)
• Steep time: 4 minutes before breaking crust
• Evaluation: Score fragrance/aroma, flavor, aftertaste, acidity, body, balance, uniformity, clean cup, sweetness, overall

Specialty Grade Cupping Requirements

Practical Inspection Protocol for Importers

Here's a systematic approach to evaluating green coffee samples:

Step 1: Visual Inspection

• Examine overall color consistency (blue-green for fresh washed, yellow-brown for naturals)
• Look for obvious defects, foreign matter, broken beans
• Assess uniformity of size and shape
• Note any unusual odors (musty, fermented, chemical)

Step 2: Defect Count

• Weigh out 300-350g representative sample
• Sort and count Category 1 defects separately
• Sort and count Category 2 defects
• Calculate defect score per 300g or 350g as appropriate
• Compare against grade specifications

Step 3: Physical Measurements

• Measure moisture content (multiple readings)
• Check water activity if equipment available
• Screen size distribution if relevant to spec
• Density measurement for altitude confirmation

Step 4: Roast and Cup

• Sample roast to light/medium (Agtron 58-63)
• Count quakers in roasted sample
• Conduct proper cupping evaluation
• Score according to SCA protocol
• Note any cup defects or off-flavors

Red Flags: When to Reject a Lot

Not every lot that meets grade specifications will work for your needs. Watch for these warning signs:

• Any Category 1 defects in specialty-grade samples
• Moisture above 13% - storage risk too high
• Musty or chemical odors in green - won't roast out
• Significant variation between sample and pre-shipment
• Excessive quakers in roasted sample (>5% of beans)
• Cup defects like ferment, phenol, or rio
• Sample doesn't match documented origin/process

Working with Your Supplier on Quality

Quality control is a partnership between buyer and supplier. Here's how to build productive relationships:

• Communicate specifications clearly - grade, moisture range, screen size requirements
• Request type samples before committing to volume
• Require pre-shipment samples that match the actual lot
• Provide feedback on arrivals - positive and negative
• Build long-term relationships with reliable suppliers

At Ethio Coffee Export, we welcome detailed QC discussions. Understanding what our buyers need helps us select the right lots and maintain the direct relationships with farmers that ensure consistent quality.

Conclusion: Quality as a Competitive Advantage

Developing strong green coffee quality control skills isn't just about avoiding bad lots it's about building the confidence to identify exceptional value and make decisions that strengthen your business. Whether you're evaluating your first Ethiopian samples or refining an established QC program, the fundamentals remain the same: systematic inspection, proper measurement, and honest sensory evaluation.

Understanding quality control also deepens your appreciation for what happens at origin. The agricultural practices, processing decisions, and commercial logistics that bring Ethiopian coffee to your door all influence the quality you receive. The more you understand these connections, the better partner you become for your suppliers and your customers.

Quality coffee is never an accident. It results from intentional decisions at every stage of the supply chain. By investing in your QC capabilities, you honor that effort and ensure the exceptional coffees of Ethiopia reach consumers as their producers intended.