Moisture Diffusion in Passion Fruit Seeds under Infrared Drying

Abstract

In order to contribute for a better understanding of the moisture diffusion in infrared (IR) drying of residual seeds from passion fruit processing, the effective moisture diffusivity (Deff) in the particles was determined from experimental drying kinetics using two different approaches, in which it is considered either as a constant parameter during the process or as dependent on moisture ratio (XR). Experiments were conducted with the seeds arranged in a single layer and exposed to three IR source temperature levels (50, 65 and 80°C). The IR source was set at a distance of 15 cm from the samples. The average effective moisture diffusivity was in the range from 2.76 x 10-11 to 11.03 x 10-11 m2 s-1. The activation energy for IR drying was 53.3 kJ/mol. Results of Deff as a function of XR, obtained using the slope method, indicated that at higher IR source temperatures the vapor diffusion is the main mechanism of moisture transport, while at lowest drying temperature, the process is controlled by both liquid and vapor diffusion.