NIRS determines caffeine and moisture without any chemicals

For coffee roasteries, continuous analysis of roasted coffee beans can have a significant financial impact. Continuous monitoring allows optimization of roasting settings for more energy-efficient processes and highly homogeneous final products. Laborious methods such as HPLC (high-performance liquid chromatography) for determining caffeine concentration require detailed knowledge of instrument operation, involve chemicals, and can take a long time for sample preparation and analysis.

Near-infrared spectroscopy (NIRS) is a fast, chemical-free alternative for analyzing caffeine and moisture in roasted coffee beans. The NIRS solution is easy to use, requires no sample preparation, and such analyzers can operate either near the roastery or in a quality control laboratory.

EXPERIMENTAL EQUIPMENT A total of 168 roasted coffee samples were analyzed using the Metrohm OMNIS NIR Analyzer Solid with a small OMNIS NIR cup, 60 mm in diameter. Whole or ground bean samples were placed in the small cup and analyzed in diffuse reflectance mode. Reference values for caffeine and moisture were obtained using appropriate primary methods. Caffeine analysis was performed using ion chromatography (IC) following ISO 20481 guidelines, and moisture analysis followed AOAC 979.12 guidelines.

The obtained NIR spectra were used to develop prediction models for various reference parameters. Correlation plots showing the relationship between NIR predictions and reference values are presented in the figures, along with the corresponding measurement values (FOM).

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