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Alkaloids: caffeine and trigonelline

This topic explains the main alkaloids in green coffee—caffeine and trigonelline—their roles in plant defense, human perception, and how they transform during roasting.

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Article 3 of 12 in Green Coffee Chemistry & Aging/
Alkaloids: caffeine and trigonelline

Caffeine

  • Content: ~1.0–1.5% in Arabica, ~2.0–4.0% in Robusta.
  • Role in plant: Natural insecticide and antifungal compound.
  • Physiological effect: Stimulant; blocks adenosine receptors in humans, increasing alertness.
  • Flavor contribution: Slight bitterness but not primary flavor driver.
  • Roasting impact: Relatively stable; little degradation even at dark roasts.

Trigonelline

  • Content: ~0.6–1.2% of green coffee.
  • Role in plant: Secondary metabolite; contributes to nitrogen storage.
  • Flavor contribution: Mild bitterness in green state.
  • Roasting impact: Highly reactive:
  • Degrades into nicotinic acid (niacin, Vitamin B3), contributing to nutritional value.
  • Produces aromatic compounds like pyridines, responsible for sweet, roasty, caramel-like notes.

Interaction with Cup Quality

  • Arabica vs Robusta: Higher caffeine in Robusta → harsher, more bitter taste.
  • Trigonelline breakdown products add complexity, sweetness, and aromatic depth in roasted coffee.
  • Excessive trigonelline degradation (very dark roasts) → bitter, smoky flavors.

Storage & Aging Effects

  • Caffeine remains stable during long storage.
  • Trigonelline slowly degrades, reducing potential for aromatic development in roasting.

Market & Consumer Relevance

  • Caffeine: Drives consumer choice (decaf vs regular; Arabica vs Robusta blends).
  • Trigonelline: Though less known, critical for roasting chemistry and flavor complexity.

Lasting Importance

Caffeine and trigonelline are key alkaloids shaping coffee’s physiology, chemistry, and sensory impact. Caffeine influences stimulation and bitterness, while trigonelline provides the foundation for aroma development and flavor depth during roasting.

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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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