Heat Pump Drying of Nutmeg Pericarp: Engineering Properties, Drying Kinetics, and Haghi-Angiz-II Modelling for Process Optimisation

This study investigates the engineering properties of nutmeg pericarp and develops a mathematical model to describe its drying behavior in a heat pump dryer. Nutmeg pericarp, an underutilized part of the nutmeg fruit, is a rich source of phytochemicals but is highly perishable, necessitating immediate postharvest drying for further processing. Drying experiments were conducted at a controlled temperature of 55°C and a relative humidity of 37%. Regression modeling was used to analyze the drying kinetics, utilizing MATLAB R2020a and R Studio software. Various statistical metrics, including the coefficient of determination (R²), adjusted R², and root mean square error (RMSE), were evaluated to determine the predictive accuracy of different thin-layer drying models. Among the models assessed, the Haghi and Angiz-II model best fit the experimental data, achieving the highest R² value of 0.999. A scatter plot comparing the experimental and predicted moisture ratios further confirmed the reliability of this model. The effective moisture diffusivity ranged from 2.1 × 10⁻⁸ to 9.08 × 10⁻⁸ m²/s. Additionally, the quality assessment indicates that heat pump drying positively influences the key quality attributes of nutmeg pericarp.