Abstract: To enhance the hot-air drying efficiency of carrots and improve the quality of dried products, this study systematically investigated the effects of alternating-current vacuum glow discharge cold plasma (CP) pretreatment at different combinations of power and time on the drying characteristics, comprehensive quality, microstructure and metabolomics of carrot slices. The results showed that CP pretreatment significantly shortened the drying time by 39.2%–54.3% and reduced the specific energy consumption (SEC) by 38.7%–47.8%. The Midilli model was the optimal model for fitting the drying process, and the pretreatment remarkably increased the effective moisture diffusivity (by up to 228.5%). In terms of quality attributes, CP pretreatment effectively improved the color of dried samples by lowering the total color difference and increasing the redness and saturation. Meanwhile, the rehydration ratio was significantly promoted (by up to 39.9%), accompanied by elevated texture hardness and resilience. The total phenolic content increased markedly (by up to 38.1%), while the total flavonoid content decreased slightly. Microstructural observations indicated that the etching action of CP formed abundant micropores and interconnected channel networks both on the surface and in the interior of samples, which provided a structural prerequisite for enhanced mass transfer and improved drying and rehydration properties. Metabolomic analysis demonstrated that at the molecular level, CP pretreatment altered the metabolomic profile of carrot samples. The CP treatment at 300 W for 300 s exhibited the highest enrichment abundance of functional metabolites. Compared with the control group, terpenoid and vitamin contents rose by 21.26% and 27.63% in the treatment group respectively, which was directly related to its excellent color and nutrient retention capacity. In conclusion, CP pretreatment is an eco-friendly technology that enables synchronous quality improvement, efficiency enhancement, and energy conservation during carrot hot-air drying. The findings provide effective references and a theoretical basis for the high-quality processing of dried carrots and other fruits and vegetables.

Key words: carrot; cold plasma pretreatment; drying quality; microstructure; metabolomics