Unraveling the Mechanisms of Quality Enhancement in Tiger Nuts (Cyperus esculentus L.) via Microwave Pulsed Vacuum Drying: Insights from Metabolomics

Tiger nut (Cyperus esculentus L.) is rich in nutrients and possesses significant economic value. However, it is susceptible to mold growth and quality deterioration after harvest due to its high moisture content. Exploring efficient quality-preserving drying techniques is of great significance for enhancing its postharvest value. In this study, a novel microwave pulsed vacuum drying (MPVD) technique was used and compared with hot air drying (HAD), natural drying (ND), and freeze-drying (FD) to analyze the effects of different drying methods on the physicochemical properties, active components, antioxidant capacity, and metabolic profile of Cyperus esculentus L. The results showed that samples treated by MPVD had the highest total phenolic content (14.47 mg GAE/g DW) and ABTS⁺ radical scavenging capacity. Furthermore, MPVD-treated samples exhibited a significantly higher flavonoid content (32.55 mg RE/g DW) than that processed by HAD and ND (P<0.05). The Metabolomics analysis revealed that MPVD and FD significantly influenced key pathways such as flavonoid biosynthesis and phenylpropanoid metabolism, promoting the accumulation of beneficial metabolites like catechin and rutin. Principal component analysis showed significant differences in metabolite composition among different drying methods, with the MPVD-treated products having the highest total number of metabolites (3162). Orthogonal partial least squares discriminant analysis further confirmed the advantages of MPVD and FD in maintaining metabolic homeostasis. This study reveals the mechanism by which MPVD enhances the quality of Cyperus esculentus L. at the metabolic level, providing a theoretical basis for its industrial processing.