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Oxidation and staling pathways

This topic explains how oxidation and staling occur in green coffee, the chemical pathways involved, and their impact on flavor, quality, and shelf life.

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  • Coffee Basics Nerds
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Article 5 of 12 in Green Coffee Chemistry & Aging/
Oxidation and staling pathways

What is Oxidation in Green Coffee?

  • Oxidation = chemical reactions between oxygen and compounds in coffee.
  • Primary targets: lipids, chlorogenic acids, and proteins.
  • Leads to loss of aromatic precursors and development of rancid or woody notes.

Lipid Oxidation

  • Lipids (~10–15% of green coffee) are vulnerable to oxygen.
  • Oxidation produces aldehydes and ketones → cardboard, rancid, stale flavors.
  • Accelerated by heat, light, and poor packaging.

Polyphenol Oxidation

  • Chlorogenic acids break down into quinic and caffeic acids.
  • Contributes to bitterness, loss of brightness, and astringency.
  • Reduces antioxidant potential of coffee.

Protein and Sugar Degradation

  • Proteins oxidize, reducing availability of amino acids for Maillard reactions during roasting.
  • Sugars degrade, lowering sweetness and caramelization potential.

Staling Pathways

  1. Autoxidation: Spontaneous reaction of lipids with oxygen.
  2. Photo-oxidation: Light exposure accelerates degradation.
  3. Enzymatic oxidation: Residual enzyme activity in poorly dried/stored beans.
  4. Moisture-driven reactions: High humidity accelerates all pathways.

Sensory Effects of Staling

  • Flat, woody, papery, or earthy cup profile.
  • Diminished sweetness and acidity.
  • Reduced aroma complexity.

Factors Accelerating Staling

  • High storage temperature (>25°C).
  • Fluctuating humidity (causes condensation and microbial growth).
  • Oxygen permeability of packaging (jute bags without liners).
  • Long storage times (9+ months for specialty lots).

Prevention Strategies

  • Use hermetic packaging (GrainPro, Ecotact) to limit oxygen exposure.
  • Store in cool, stable environments (18–22°C).
  • Maintain moisture at 10–12% and a-w 0.55–0.65.
  • Implement FIFO (first in, first out) rotation.

Lasting Importance

Oxidation and staling pathways are the main enemies of green coffee quality. By understanding and controlling them, producers and buyers can extend shelf life, preserve flavor integrity, and ensure that coffee reaches roasters fresh, aromatic, and true to its terroir.

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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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