QA/QC of coffee using the Agilent Cary 630 ATR-FTIR analyzer

Importance of the Topic

Coffee is one of the most widely consumed beverages worldwide, prized for its flavor, aroma and stimulating effects. The roasting process alters bean moisture, density, color and chemical composition, directly impacting taste and quality. Rapid and reliable quality assurance is essential to authenticate incoming lots, prevent off-flavors and ensure consistency throughout packaging and distribution.

Study Goals and Overview

This application note demonstrates the use of an ATR-FTIR analyzer for on-site QA/QC of ground coffee. The objectives were to build a spectral library of commercial coffee brands, validate the repeatability of measurements and enable immediate pass/fail decisions based on spectral matching.

Methodology

• Commercial ground-coffee samples were obtained from various grocery stores.
• Each sample was applied directly to the diamond attenuated total reflectance (ATR) crystal of the Agilent Cary 630 ATR-FTIR analyzer.
• Spectra were acquired in under 30 seconds (64 scans at 4 cm⁻¹ resolution).
• Reference spectra were stored in the Agilent MicroLab FTIR software database.
• Unknown samples were compared automatically to the library, yielding pass/fail or percentage similarity results.

Used Instrumentation

Agilent Cary 630 ATR-FTIR analyzer with diamond ATR accessory and Agilent MicroLab FTIR software for data acquisition, spectral storage and automated search functionality.

Results and Discussion

• All coffee brands produced characteristic infrared bands between 1800 and 800 cm⁻¹, corresponding to C=O stretching from esters, lactones, aldehydes, ketones and acids.
• C-H bending of lipids was observed at 1470–1430 cm⁻¹; strong carbohydrate absorptions appeared at 1200–900 cm⁻¹.
• The fingerprint region below 1400 cm⁻¹ provided unique patterns for each brand.
• Duplicate samples were correctly matched, and unknown lots were accurately identified by the software’s search function.

Benefits and Practical Applications

• No chemical reagents or sample preparation are required.
• Rapid analysis (<30 seconds per sample) enables immediate decision-making.
• On-site testing at receiving docks, process lines or supplier facilities.
• Reliable authentication of coffee batches to maintain consistency and prevent fraud.

Future Trends and Potential Applications

• Expanded spectral libraries to include defect detection, roast level classification and geographical origin.
• Chemometric modeling for detailed grouping (e.g., Arabica vs. Robusta, organic vs. conventional).
• Integration of portable FTIR devices for field or in-package testing.
• Extension of the approach to other food matrices, process monitoring and quality control of decaffeination or lipid oxidation.

Conclusion

The Agilent Cary 630 ATR-FTIR analyzer offers a fast, reliable and reagent-free method for coffee quality control and authentication. By comparing incoming sample spectra to a reference library, operators can perform on-site pass/fail assessments within seconds, enhancing QA/QC efficiency and product consistency.

Reference

• Craig AP, Franca AS, Oliveira LS. Evaluation of the potential of FTIR and chemometrics for separation between defective and non-defective coffees. Food Chemistry. 2012;132:1368–1374.
• Gordillo-Delgado F, Marín E, Cortés-Hernández DM, Mejía-Morales C, García-Salcedo AJ. Discrimination of organic coffee via Fourier transform infrared–photoacoustic spectroscopy. J Sci Food Agric. 2012. DOI:10.1002/jsfa.5628.
• Lyman DJ, Benck RM, Merle SF. Difference spectroscopy in the analysis of the effects of coffee cherry processing variables on the flavor of brewed coffee. Int J Spectroscopy. 2011;2011:815304.
• Innawong B, Mallikarjunan P, Irudayaraj JQ, Marcy JE. The determination of frying oil quality using Fourier transform infrared attenuated total reflectance. LWT — Food Sci Technol. 2004;37:23–28.