Cold Plasma Pretreatment Prior to Ultrasound-assisted Air Drying of Cumin Seeds

This study was undertaken to investigate the effect of cold plasma (CP) and ultrasound wave (US) before and during air drying of cumin seeds, respectively. In this regard, different CP exposure times (15 and 30 s), sonication powers (60, 120, and 180 W), and drying air temperatures (30, 35, and 40 degrees C) were practiced at the velocity of 0.6 m/s to study the underlying changes in drying time, effective moisture diffusivity, energy consumption, total color change, rupture force, and microstructure of cumin (Cuminum cyminum L.) seeds. It was found that CP pretreatment significantly increased effective moisture diffusivity and reduced drying time, energy consumption, and color change in the cold plasma-assisted drying program (CPCV). The morphological alteration in the seeds' surface, which accelerates water removal from the inner structure toward the surface, is the main cause of CP-induced modification in the drying process. The positive effect of CP pretreatment on the cumin seeds was intensified when it was followed by high-power sonication during air drying of the seeds. So that, the maximum reductions in drying time (46.65%), energy consumption (39.49%), total color change (40.69), and rupture force (46.84%) were in possession of 15 s CP pretreatment before ultrasound-assisted drying at the power level of 180 W. Longer exposure time (30 s) resulted in denser material with the compacted surface resulting in less color retention and increased rupture force.

Automated summary

This study found that cold plasma pretreatment significantly increased the effective moisture diffusivity and reduced drying time, energy consumption, and color change in cumin seeds. This was attributed to the morphological alteration in the seeds' surface, which facilitated water removal. Additionally, the positive effect of cold plasma pretreatment was intensified when combined with high-power sonication during air drying.