Unlocking the "Other" Flavors in Coffee: Navigating Chemical & Papery Musty Notes on the SCA Flavor Wheel

Within coffee’s flavor universe, sweetness, fruitiness, and floral aromas often steal the spotlight. But the SCA Flavor Wheel also features a less glamorous yet vital category: “Other” flavors, including Chemical and Papery/Musty. Though often associated with faults, these flavors can influence quality evaluation and point to opportunities for process improvement.

This deep dive will explore what these flavors signify, their chemical origins, and how to recognize them—drawing from sensory science and SCA-aligned research.

 

Understanding the "Other" Category

The SCA Flavor Wheel’s “Other” section encompasses descriptors like Chemical (solvent-like), Papery, and Musty/Dusty—offering a way to pinpoint off-notes that fall outside pleasant flavor categories. These often appear on the outer ring as part of the Chemical and Papery/Musty subcategories.

 

Why These Flavors Matter

While sweet or fruity notes are linked to quality, “Other” flavors often signal bean defects, poor processing, or staling. Documenting them helps:

• Maintain quality control
• Troubleshoot roasting, processing, or storage issues
• Avoid passing off flawed batches to customers

 

Spotlight on Key Subcategories

Flavor Descriptor	Description	Potential Cause
Chemical	Nail polish, solvent-like	Over-fermentation, chemical residue
Papery/Musty	Wet cardboard, dusty, old book	Staling, mold, poor storage

 

Chemical Notes

Often likened to nail polish remover or solvents. These develop when green beans pick up foreign chemicals during processing, storage, or handling. These damages persist through roasting, resulting in off-aromas and harsh mouthfeel.

The presence of chemical notes serves as a red flag, prompting coffee professionals to revisit post-harvest hygiene and cleaning protocols.

 

Papery/Musty Notes

Smelling of stale paper, cardboard, or dusty rooms, these notes result from oxidation (aging) or mold/mildew contamination.

A study in the SCA Coffee Staling Report confirms that as coffee ages, lipid oxidation yields compounds like hexanal, which are tied to musty or rancid aromas. Additionally, the World Coffee Research Sensory Lexicon lists these descriptors alongside moisture-related notes like "Musty Earthy" and "Moldy Damp".

 

Chemical & Papery in the Context of Sensory Science

Research shows coffee becomes noticeably moldy or stale after just a few months when exposed to air. Studies suggest oxygen levels under 0.5% preserve flavor significantly longer. Still, the sooner notes of papery/musty appear, the more intervention is needed in packaging, storage, or roasting protocols.

 

Detecting “Other” Flavors

1. Dry Aroma: Sniff the grounds—do they smell stale, dusty, or plasticky?
2. Wet Crust: During cupping, inhale again once water is added. Musty or chemical aromas may emerge.
3. Tasting: Take a slurp—chemical notes often trigger a sharp, lingering bite; papery notes may feel dull and flat.
4. Aftertaste: Do stale or musty notes linger unpleasantly? If so, investigate potential quality issues upstream.

 

Common Triggers in Quality Control

• Harvest/Processing Errors: Over-fermentation produces chemical byproducts.
• Inadequate Drying: Trapped moisture leads to mold, musty flavors.
• Poor Storage: Oxidation from high oxygen exposure accelerates staling.
• Roast & Packaging: Dark roasts or porous packaging can increase chemical breakdown.

 

Avoiding & Managing These Flavors

Bean Selection

• Opt for well-sorted, defect-free green beans.
• Use freshness indicators; avoid those with “beany” or raw smell.

Processing

• Ensure thorough washing and drying.
• Avoid long fermentation.
• Use shaded, dry storage to prevent mold.

Roasting & Cooling

• Monitor roast progress; don’t leave beans in roast chamber to cool slowly.
• Cool beans with clean, circulated air to avoid off-flavors.

Packaging & Storage

• Use one-way valves, low-oxygen packaging.
• Store at cool temperatures and steady humidity.

 

Why Professionals Should Care

For roasters and importers, detecting and eliminating “Other” flavors protects brand reputation and ensures consistency. Customers won’t complain about “winey” or “nutty” notes, but they will notice plastic or musty aftertaste—and won’t return.

Quality control protocols should include sensory checks for these categories, using the SCA Flavor Wheel to train cupping panels to identify and react accordingly.

 

Practical Steps for Sensory Panels

1. Calibration – Use reference compounds like hexanal for papery/musty, and solvent essences for chemical notes.
2. Blind Cupping – Introduce samples with known defects to train panelists.
3. Documentation – Record scores and investigate batches with high levels of these flavors.
4. Intervention – Adjust sourcing, drying, roasting or packaging processes based on results.

 

Conclusion

While overshadowed by more desirable flavor notes, Chemical and Papery/Musty descriptors are critical quality markers. Their presence signals breakdown in the coffee value chain—processing, storage, or roast—that demands attention.

Using the SCA Flavor Wheel and sensory science, roasters can proactively detect, control, and prevent these negative flavors, enhancing the quality, consistency, and reputation of their coffee.