Comparative Analysis of Volatile Organic Compounds in Herbaceous and Fruity Pitaya (Selenicereus undatus) Cultivars During Ripening via GC × GC-TOF-MS

Different pitaya cultivars (Selenicereus undatus) have unique aroma characteristics. For example, the “Vietnamese White Heart” pitaya fruit exhibits a distinct “herbaceous aroma”, while the new variety “Yuehong No. 6” exhibits a “fruity aroma”, but the underlying mechanisms remain unclear. This study aimed to characterize and compare the developmental changes in volatile organic compound (VOC) profiles between two pitaya cultivars at 25, 30, and 35 days after flowering (DAF), using GC × GC-TOF-MS combined with relative odor activity value (ROAV) analysis. The results show that the ROAVs of 2-pentylfuran and (E)-2-octenal increased progressively in “Vietnamese White Heart” but decreased during development in “Yuehong No. 6”. Although their ROAVs were higher in “Yuehong No. 6” at 25 and 30 DAF, this pattern was reversed at 35 DAF. At 35 DAF, 2-undecanone also showed a higher ROAV in “Vietnamese White Heart”, whereas 2-dodecenal showed a higher ROAV in “Yuehong No. 6”. This study reveals cultivar-dependent developmental trajectories of several potentially aroma-relevant VOCs, and provides a basis for future flavor-oriented molecular breeding, harvest timing optimization and fruit processing.