Infrared drying kinetics of Capsicum annuum L. var. glabriusculum (Piquin pepper) and mathematical modeling

Abstract

In this work, the dehydration kinetics of Capsicum annuum L. var. glabriusculum (Piquin pepper) was studied at three different temperatures (70 C, 80 C, and 90 C) during infrared drying using a moisture analyzer. A mathematical model was used to predict the experimental data, which are related to the apparent effective moisture diffusivity coefficient (D eff ). It was observed that by increasing the drying temperature from 70 C to 90 C, drying time decreased from 160 to 70 min, taking place in the falling rate stage; however, browning of the product was observed at 90 C. Piquin pepper's initial free-water percentage was found to be 96.4% w/w. Experimental drying behavior agrees well with the single-layer Gruintal-Santos model that was related to D eff obtaining values in the interval of 1.53 Â 10 À10 to 3.23 Â 10 À10 m 2 /s increasing with the temperature, which is comparable with reported values for similar drying processes of peppers. From 70 C to 90 C, the initial free water ranged from 4.72 to 4.88 kg of free water/kg of dry solid, while equilibrium free water changed from .2093 to .0526 kg of free water/kg of dry solid. The activation energy was estimated as 38.812 kJ/mol. Practical applicationsDrying kinetics and moisture diffusivity coefficient have not been reported for Capsicum annuum L. var. glabriusculum (piquin pepper). In this work, we report the infrared kinetics drying and its mathematical modeling to estimate the moisture diffusivity coefficient as a function of drying temperatures. The results of D eff can be used for the large-scale dryer design.