Effect of cold atmospheric plasma pretreatment on phytochemical content and microstructure of beetroot during intermittent microwave hot-air drying

Thermal degradation of phytochemicals in heat-sensitive foods necessitates development of innovative drying strategies. This study investigated the application of dielectric barrier discharge (DBD) plasma pretreatment on intermittent microwave-hot air (IMHA) drying for beetroot slices. Scanning electron microscopy showed that DBD-plasma pretreatment generated surface microchannels and increased porosity by 27%, thereby facilitating moisture removal. The optimal conditions depended on the processing objective: the highest drying efficiency was achieved with 5 min of DBD-plasma pretreatment at 600 W and a pulse ratio (PR) of 1, reducing the total drying time by 34%, whereas the highest phytochemical retention was obtained at 180 W and PR of 2, yielding 55.2% higher betacyanin content, 33.8% greater antioxidant activity, and 43.7% higher total phenolic content. These findings highlight the potential of integrating DBD-plasma pretreatment with IMHA drying to improve drying efficiency and preserve product quality. From an industrial perspective, this approach may support the production of dried beetroot with improved functional quality and shorter processing time. A limitation of this study is that the process was evaluated at laboratory scale; therefore, further pilot-scale validation is required to confirm scalability.