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Electronic color sorting basics

This topic explains the basics of electronic color sorting in coffee milling, how the machines work, and why they are essential for defect removal and consistency in specialty coffee exports.

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Article 4 of 12 in Milling, Sorting & Grading/
Electronic color sorting basics

What is Electronic Color Sorting?

  • An automated step in dry milling where beans are inspected by optical sensors and sorted by color.
  • Removes defective beans that differ in color from the desired lot standard.
  • Increases consistency, reduces labor, and supports specialty-grade quality.

How It Works

  1. Beans flow down a chute in a thin layer.
  2. High-speed cameras or optical sensors scan each bean.
  3. Defective beans (too dark, too light, discolored, insect-damaged) are detected.
  4. Compressed air nozzles eject defective beans into a separate channel.

Types of Defects Removed

  • Black beans (over-fermented, insect damage).
  • Sour beans (yellowish, defective fermentation).
  • White beans (immature or bleached).
  • Foreign matter (stones, husks, sticks).

Advantages

  • Fast and highly accurate compared to hand sorting.
  • Ensures visual and physical uniformity.
  • Essential for meeting specialty buyer standards.
  • Reduces labor intensity in large mills.

Limitations

  • High equipment and maintenance cost.
  • Requires skilled technicians to calibrate and operate.
  • Some subtle defects (e.g., phenolic taints) not visible by color alone.

Integration with Other Sorting Steps

  • Used after screen size and density separation for maximum accuracy.
  • Final polish in preparing export-ready lots.

Market & Quality Benefits

  • Supports higher cupping scores by eliminating defective beans.
  • Ensures consistency across lots → builds buyer trust.
  • Increases acceptance rates in strict importing countries.

Lasting Importance

Electronic color sorting is a key innovation in modern coffee milling. By automating defect removal, it enhances both efficiency and quality, ensuring that carefully processed coffee meets the visual and sensory expectations of global specialty markets.

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Coffee Basics Nerds

Written by : Coffee Basics Nerds

Expert coffee historians and brewing enthusiasts dedicated to sharing the rich heritage and techniques behind your perfect cup of coffee.

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