CONVECTIVE DRYING KINETICS OF YACON (Smallanthus sonchifolius Poepp. Endl.) SLABS AND EVALUATION OF THE DRYER PID TEMPERATURE CONTROL SYSTEM

Abstract

Yacon is a functional food that is rich in fructooligosaccharides (FOS) and highly perishable, which requires inexpensive methods for its preservation. The objectives of this research were to model the kinetics of convection drying of yacon slabs and to assess the effect of air velocity on the temperature record of the heating zone controlled by the Proportional-Integral-Derivative control system (PID). Different temperatures (60, 70, and 80 °C) at constant air velocity (0.87 m s-1) were evaluated in a convective tray drying system. To determine the effect of air velocity on the PID temperature controller, different air velocities (0.81-2.06 m s-1) at constant temperature (70 °C) were studied. The results showed that Page’s model was the best fitting of the data obtained, the effective diffusivity of convective drying of yacon ranged from 1.22x10-10 to 1.9x10-10 m2 s-1 and the activation energy was 21.76 kJ mol-1. With PID temperature control, it was observed that the best drying rate and lowest temperature signal error occurred at an air velocity of 1.46 m s-1, where the temperature signal was more stable and closer to the reference temperature. In conclusion, the kinetic modeling of the convective drying of yacon provides optimal drying parameters as well as behavior of mass and heat transfer phenomena, particularly considering that the effect of air velocity influences the drying kinetics and the PID temperature control of the dryer.