Experimental investigations and modeling of vacuum oven process using several semi-empirical models and a fuzzy model of cocoa beans

An experimental study combined with a mathematical modeling of vacuum drying of cocoa beans was carried out to enhance the drying kinetics without compromising the quality of dried products. Experiments were conducted to compare the effects of variation of temperature and pressure on the drying process. The temperature was varied between 40 and 60 °C, while the pressure between 735 and 245 mmHg. The experimental study investigated and analyzed the effects of various process parameters on drying kinetics and quality (in terms of color and pH value). Results demonstrated that the cocoa beans dried at 50 °C temperature and 735 mmHg pressure had the highest drying kinetics, lowest acidity, and best color among all the temperature and pressure values. Compared to convective drying conducted at 60 °C temperature and atmospheric pressure (760 mmHg), vacuum oven drying consistently showed better drying performance with a higher quality of dried products. Modeling for vacuum drying kinetics of cocoa beans was performed with semi-theoretical drying kinetic and fuzzy models to verify the experimental results. The graphical representations of the results demonstrated a good fit between the fuzzy model and the experimental data compared with semi-theoretical drying kinetic models. Finally, a suitable model was proposed for optimum drying conditions compared with the fuzzy and drying kinetic models that could play an important role in designing future advanced dryers.