A reliable tool based on near-infrared spectroscopy for the monitoring of moisture content in roasted and ground coffee : A comparative study with thermogravimetric analysis

Moisture content (MC) is one of the main issues that the coffee industry has to monitor. The international standards (ISO 11817 and ISO 11294) for MC evaluation are incompatible with the rhythm of a modern productive chain. As an alternative, thermogravimetric moisture analyzers (TMA) are widely applied, but they cannot provide a real-time monitoring and management of MC. The present research aims at evaluating the performance of a near-infrared (NIR) spectrophotometer in measuring the MC of roasted beans and ground coffee, in comparison with a TMA. PLS regression models provided high predictive performances (R2Pred = 0.95 and RMSEP = 0.15%, and R2Pred = 0.97 and RMSEC = 0.13% for roasted and ground coffee, respectively). Passing-Bablok regression was performed to compare NIR and TMA measurements, but no significant differences were highlighted. The residual dispersion index (RDI%) was proposed, showing the higher predictive accuracy of the NIR spectrophotometer, envisaging this technology as a routine standard method for coffee MC evaluation.