Coffee

1. Brief Description

Coffee (Coffea arabica and Coffea canephora / robusta) is one of the most traded agricultural commodities in the world, grown across a “coffee belt” spanning Latin America, Africa and Asia. Its quality is defined by a combination of physical grading (bean size, defect count, color uniformity) and chemical composition (moisture, caffeine, chlorogenic acids, lipids, sucrose), which together determine cup quality, market grade (specialty vs. commercial) and price.

Quality assessment traditionally relies on manual green-bean grading (counting primary and secondary defects against reference standards), moisture meters, and, for specialty coffee, trained cupping panels that score aroma, acidity, body and aftertaste following protocols such as the SCA (Specialty Coffee Association) cupping form.⁴ Chemical composition is verified through wet-chemistry or chromatographic lab methods (HPLC for caffeine and chlorogenic acids, Soxhlet extraction for lipids). These methods are informative but slow, subjective in the case of grading/cupping, or destructive and costly in the case of lab chemistry.^1,5

2. The Problem

Traditional coffee quality control faces several vulnerabilities across the supply chain:

• Subjectivity of grading and cupping: defect counting and sensory cupping depend on trained graders and Q-graders, whose scores can vary between individuals and sessions, and which cannot be applied exhaustively to every lot.⁴
• Heterogeneity of green coffee lots: deliveries from different farms, processing methods (washed, natural, honey) and moisture levels are often mixed, making it hard to characterize a lot quickly before pricing or roasting.³
• Moisture and safety limits: green coffee moisture content must stay within a narrow safe range (roughly 8.0 to 12.5%); beans outside this range are prone to mold growth (including mycotoxin risk) and are not permitted for shipment, yet moisture meters give only a partial picture of overall quality.²
• Fraud and adulteration: given the price gap between specialty-grade and commercial-grade coffee, and between pure and adulterated products (fillers, foreign matter, undeclared robusta blended into arabica, decaffeination claims), there is incentive for misrepresentation at multiple points in the chain.^3,6
• Cost and turnaround of lab chemistry: HPLC-based caffeine and chlorogenic acid analysis, or Soxhlet lipid extraction, are accurate but slow, require solvents and trained personnel, and are impractical for routine screening of every incoming lot or roast batch.¹
• Roast consistency: roasters need fast feedback on caffeine and moisture to fine-tune roast profiles for energy efficiency and consistency, but conventional lab methods introduce a lag that limits real-time process control.^5,7

3. How NIR Can Contribute at Each Step

The value chain runs from the farm to the roasted, packaged product. NIR can be applied at several key stages, replacing subjective grading/cupping or slow lab chemistry with fast, non-destructive, objective measurements, provided the models are properly calibrated and validated.^1,3,5

Parameters that can be measured by NIR in Coffee

In a non-destructive, fast and objective way, NIR can quantify several of the traits that traditionally depended on lab chemistry, moisture meters or sensory cupping panels:

The chain, step by step

• 1. Cultivation. Coffee is grown on farms (often smallholders) at altitude, under shade or full sun, with arabica or robusta varieties chosen according to climate, altitude and target market.
• 2. Harvest. Ripe cherries are hand-picked (selective, for higher quality) or stripped/mechanically harvested, with ripeness at picking directly affecting cup quality potential.
• 3. Processing (wet, dry or honey). Cherries are processed to remove the pulp and mucilage: washed (fermented and rinsed), natural (dried whole), or honey (partial mucilage retained), each imparting a distinct flavor profile.
• 4. Drying. Parchment coffee is dried, on patios, raised beds or mechanical dryers, to a safe moisture level before hulling.²
• 5. Hulling and grading at origin. The parchment layer is removed to reveal the green bean; beans are then sorted by size, density and defect count, and classified into export grades.^3,4
• 6. Local trading / cooperative collection. Cooperatives or local traders purchase parchment or green coffee from farmers, often blending lots before onward sale.
• 7. Export. Green coffee is bagged, certified (organic, fair trade, geographic indication, etc. where applicable) and shipped in containers to importing countries.
• 8. Import and storage. Importers or traders receive the green coffee, store it under controlled conditions, and distribute it to roasters.
• 9. Roasting. Roasters apply time-temperature profiles to develop the bean’s aroma and flavor, closely monitoring moisture loss and chemical transformation throughout the process.^5,7
• 10. Grinding and packaging (where applicable). Roasted beans are ground to the required particle size (or left whole) and packaged for retail, foodservice or industrial use (including instant coffee processing).
• 11. Distribution and retail. Roasted or instant coffee is distributed to retailers, cafés and foodservice, where labels claim origin, variety, roast level and, in some cases, decaffeination status.
• 12. Final consumption. The end consumer brews and drinks the coffee, trusting the origin, freshness and quality claims on the packaging^3,6, generally with no independent way to verify them.

4. Who Can Benefit from This Technology

• Farmers and cooperatives: benefit at the post-drying / pre-sale grading step, verifying moisture and quality indicators on-site before negotiating price with buyers, without depending solely on manual defect counting.^2,4
• Local traders and exporters: benefit at the lot classification and export certification step, quickly profiling incoming deliveries to determine grade, price and suitability for specialty vs. commercial markets.³
• Importers: benefit at the goods receiving and storage step, confirming in minutes that shipments match declared moisture, species and origin before distributing to roasters.^2,3
• Roasters: benefit at the roast process control step, using fast caffeine and moisture feedback to fine-tune roast profiles for consistency and energy efficiency.^5,7
• Retailers and instant coffee producers: benefit at the finished-product QC step, confirming decaffeination claims, freshness and compositional consistency across batches.^1,6
• Certifiers / supply chain auditors: benefit at the periodic audit step, gaining an objective, repeatable tool to validate origin, species and quality claims from suppliers, faster and cheaper than traditional lab chemistry or cupping panels alone.^3,6

5. References

1. Huck CW, Guggenbichler W, Bonn GK. Analysis of caffeine, theobromine and theophylline in coffee by near infrared spectroscopy (NIRS) compared to high-performance liquid chromatography (HPLC) coupled to mass spectrometry. Anal Chim Acta. 2005;538:195-203. Available from: Anal Chim Acta 2005
2. Adnan A, von Hörsten D, Pawelzik E, Mörlein D. Rapid prediction of moisture content in intact green coffee beans using near infrared spectroscopy. Foods. 2017;6:38. Available from: Foods 2017
3. Adnan A, Naumann M, Mörlein D, Pawelzik E. Reliable discrimination of green coffee beans species: a comparison of UV-Vis-based determination of caffeine and chlorogenic acid with non-targeted near-infrared spectroscopy. Foods. 2020;9:788. Available from: Foods 2020
4. Tolessa K, Rademaker M, De Baets B, Boeckx P. Prediction of specialty coffee cup quality based on near infrared spectra of green coffee beans. Talanta. 2016;150:367-374. Available from: Talanta 2016
5. Bertone E, Venturello A, Giraudo A, Pellegrino G, Geobaldo F. Simultaneous determination by NIR spectroscopy of the roasting degree and Arabica/Robusta ratio in roasted and ground coffee. Food Control. 2016;59:683-689. Available from: Food Control 2016
6. Green S, Fanning E, Sim J, Eyres GT, Frew R, Kebede B. The potential of NIR spectroscopy and chemometrics to discriminate roast degrees and predict volatiles in coffee. Molecules. 2024;29:318. Available from: Molecules 2024
7. Esteban-Díez I, González-Sáiz JM, Pizarro C. Prediction of sensory properties of espresso from roasted coffee samples by near-infrared spectroscopy. Anal Chim Acta. 2004;525:171-182.