Ultrasonic assisted pre-treatment method for enhancing mass transfer during the air-drying of habanero chili pepper (Capsicum chinense)

Abstract

The ultrasonic pre-treatment method was used for the purpose of reducing the time employed in air-drying of habanero chili pepper. The pre-treatment was performed by immersing the sample in distilled water and applying ultrasonic signals during 30 and 60 min with a 750-Watt ultrasonic processor (20 kHz) operated at different percentages of amplitude (A) ranging between 20 and 100%. The samples immediately underwent air-drying at 60? C in a convection oven with an air velocity of 2 ± 0.2 m/s. A mathematical model that takes into account the influence of the internal resistances to mass transport by diffusion (Dw ) as well as the resistance of the membrane barrier (kc ) promoted by the wax layer of the habanero pepper was proposed to analyze the drying kinetics. The drying time following the ultrasound treatment was reduced from a 25 to a 50% compared to the results obtained in untreated samples. It was found that Dw and kc were significantly influenced by the ultrasonic pretreatment (p < 0.05). The highest drying rate was achieved in the amplitude percentage of 80 and 100% with a sonication time of 60 min. Copyright © Taylor & Francis Group, LLC.