UC Davis

The maintenance of green coffee moisture content (MCwb) within the ideal range (10-12%) during storage and transportation is crucial, as variations in MCwb will lead to degradation in coffee quality. Prolonged storage and long-distance transportation of green coffee in conventional jute sacks exposes the coffee beans to undesirable fluctuations in temperature (T) and relative humidity (RH), which can change the physical and sensory characteristics of the coffee. Thus, the primary goal of this study was to evaluate the efficacy of commercially available desiccants for preserving the moisture content of green coffee between 10-12% MCwb, when stored and transported in either hermetic packages and/or jute sacks, and to assess the corresponding impact on sensory quality. A conventional coffee storage and transportation period from Brazil to Italy with a duration of 42 days was mimicked in environmental chambers. Treatments in a 3 × 3 factorial design consisting of three packaging materials (GrainPro SuperGrain bag, GrainPro TranSafeliner, and/or jute sacks) and desiccants (Drying Beads®, CaCl2, or no desiccants) at four different mass ratios of green coffee to desiccant ranging from 50 to 300 – g coffee per g desiccant were evaluated. Overall, the results indicate that hermetic packages, even without desiccants, provide a stable MCwb for green coffee compared to jute sacks only, but under some conditions such as green coffee transportation, desiccants should be added to prevent MCwb in excess of 12%.In addition to controlling the MCwb of green coffee, accurate measurement of MCwb at the various postharvest steps is also vital. Therefore, an accurate, inexpensive prototype inline system capable of accurately measuring the MCwb of green coffee beans, using a commercially available time-domain reflectometry (TDR) probe was designed and developed. TDR was applied due to its high accuracy, flexibility, robustness, and capability of providing real-time measurements. The TDR probe was calibrated and validated with green coffee within a MCwb range of 9 to 21 %. A calibration linear regression model correlating the TDR probe output (dielectric constant) to reference MCwb measurements obtained by a halogen moisture analyzer, yielded a high coefficient of correlation (R2 =0.99). Model validation yielded a high R2, and a low Root Mean Squared Error equal to 0.93, and 0.9% MCwb, subsequently. Results indicate that the TDR inline green coffee moisture estimation system has the potential to be applied in real-time, industrial-scale operations.