Convective drying of atmospheric pressure cold plasma pretreatment saffron stigmas: kinetic modeling

In this study, the drying kinetics of saffron stigmas pretreated by atmospheric pressure cold plasma pretreatment (15, 30, 45 and 60 s) followed by hot air drying (60°C and 1.5 m/s) were modeled using 10 conventional mathematical thin layer models. The use of cold plasma pretreatment reduced drying time and enhanced effective moisture diffusivity (Deff). The most accurate models describing behavior of drying process of stigmas were Two-term, Midilli and Kucuk and Wang–Singh models. These models were determined based on the higher value of coefficient of determination (R2) and the lower values of root mean square error (RMSE), chi-square (χ2) and sum of square errors (SSE). In addition, the Newton model did not in accordance with experimental data.  The value of Deff of pre-treated saffron stigmas were in the range of 8.7013×10-9 and 9.1139 ×10-9 m2/s depending on the time of pretreatment. The use of cold plasma pretreatment reduced the surface resistance to moisture transfer, improved the diffusion coefficient, and subsequently, reduced the drying time.