Investigating effect of cold plasma pretreatment on drying kinetics, bioactive compounds, and antibacterial properties of ginger slices
Nattapong Chanchula, Kanoktip Pansuksan, Atipong Bootchanont, Chakkaphan Wattanawikkam, Dheerawan Boonyawan, Porramain Porjai
Abstract
• Cold plasma jet (CPJ) and dielectric barrier discharge (DBD) plasma pretreatment for 15 s enhanced effective moisture diffusivities. • The ginger’s pores were closed after pretreatment for a longer time, reducing effective moisture diffusivities. • Cold plasma pretreatment improved total phenolic and flavonoid contents. • Dried ginger slices pretreated with cold plasma efficiently inhibited Escherichia coli and Bacillus subtilis activities. This study investigated the effects of cold plasma jet (CPJ) and dielectric barrier discharge (DBD) plasma pretreatments (15 and 30 s) on drying properties, microstructure, bioactive compounds, and antibacterial activity of ginger slices before hot air drying at 50, 60, and 70 °C. Results showed that short-duration plasma pretreatments enhanced drying efficiency, significantly increasing effective moisture (D eff ) which highest D eff (8.14±0.25 × 10 –10 m 2 /s) was observed with DBD plasma pretreatment for 15 s at 70 °C. The microstructure illustrated that the total area and percentage of pores of ginger surface decreased under cold plasma treatment. The DBD plasma pretreatment for 30 s had the lowest total area and percentage of pores (115,893 µm 2 and 10.31 %, respectively), relating to the lowest D eff value at all drying temperatures. The modified Overhults model best described drying kinetics, exhibiting the highest regression coefficient, lowest chi-square, root mean square errors, and akaike information criterion. Cold plasma pretreatment also significantly enhanced total phenolic and flavonoid contents by 63.87 % and 59.5 %, respectively, with optimal results at CPJ treatments (30 and 15 s) at 70 °C. Furthermore, plasma-treated dried ginger slices exhibited enhanced antibacterial activity against Escherichia coli and Bacillus subtilis , which showed 1.22–1.56, 1.02–1.10, and 0.85–1.22 times higher activity than the non-treated plants at 50, 60, and 70 °C, respectively. These findings demonstrated that cold plasma pretreatment effectively improved drying performance, nutritional quality, and microbial safety of dried ginger slices. Future studies should investigate industrial scalability, economic feasibility, consumer acceptance, and potential applications for other high-value dried food products.