Ultrasound Effects on the Mass Transfer Processes during Drying Kinetic of Olive Leaves (<i>Olea Europea</i>, var. Serrana)

Abstract

The large amount of materials derived from olive trees pruning may constitute a source of compounds with antioxidant activity. The air drying of raw matter is a previous stage before extraction preserving the raw matter and avoiding the interference of water on the process but it constitutes a slow and high energy demanding process. In this sense, the application of high intensity ultrasound could affect the mass transfer rate. In order to address the influence of ultrasound on the drying process of olive leaves, air drying experiments were carried out (40°C and1 m/s) without (0 W) and with ultrasound application (8, 16, 25 and 33 kW/m3). The different drying conditions were tested by triplicate. To model the experimental data, diffusional models considering or not the external resistance to mass transfer were used. The model without considering external resistance did not fit well to the experimental data. However, the model including external resistance achieved percentages of explained variance above 99.7%. The influence of ultrasound on diffusivity was not significant but a significant dependence was found for the mass transfer coefficient, proportional to the power density applied.

Drying Kinetics, Microstructure and Antioxidant Properties of Basil Treated by Ultrasound

“…Recently, in the limited studies, the sonication was applied during drying of green leaves in order to enhance the dehydration (Cárcel et al . ; Rodriguez et al . ; Sledz et al .…”

“…Recently, in the limited studies, the sonication was applied during drying of green leaves in order to enhance the dehydration (Cárcel et al 2010;Rodriguez et al 2013;Sledz et al 2015). However, there is almost lack of research concerning utilization of US as a pretreatment prior to drying of herbal leaves and in particular microwaveconvective drying.…”

Improvement of water transport mechanisms during potato drying by applying ultrasound

“…Ultrasound‐assisted convective drying techniques have been applied to accelerate the drying of several products, including carrot,7, 11 onion,16 wheat and corn,17 rice,18 persimmon,10 eggplant,19 olive leaves,20 lemon peel11 and surimi 21. Despite all these works showed a significant ultrasonic effect on the water transport during drying, it should be remarked that the ultrasonic application becomes more or less efficient depending on the process variables, such as air velocity,10, 22 temperature23 or applied ultrasonic power 11.…”

Influence of Temperature, Air Velocity, and Ultrasound Application on Drying Kinetics of Grape Seeds

“…In gas-solid systems, like convective air drying, the high impedance mismatch and the high ultrasonic energy attenuation in air make the transmission of ultrasound from the transducer to the air and from the air to the solid difficult [10] . Nevertheless, some studies can be found in literature into high intensity ultrasound-assisted convective air drying [10,11,12,13,14] . In some cases, it has been found that over 70% less time is needed for the drying process [14] .…”