Quality and Flavor Evolution of Pugionium cornutum (L.) Gaertn. During Natural Pickling: Insights from Sensory and Physicochemical Characterizations

Pugionium cornutum (L.) Gaertn. is an underutilized Brassicaceae vegetable whose strong pungency limits its broader food-industrial application. Natural pickling can mitigate pungency and improve flavor, yet the dynamic evolution of flavor quality, physicochemical shifts, volatile profiles and sensory maturation throughout natural pickling remains poorly understood. Herein, sensory evaluation, physicochemical assays, electronic nose (E-nose), headspace gas chromatography–ion mobility spectrometry (HS-GC-IMS) and multivariate analyses were adopted to characterize its quality and flavor changes during 28-day natural pickling. The first 7 days represented the major physicochemical transformation interval, featuring rapid NaCl uptake, pH drop, increased titratable acidity (TA) and amino nitrogen (amino-N), reducing-sugar consumption, and a transient nitrite peak. Weighted sensory score increased from 42.75 (D0) to 81.84–83.98 (D21-D28). Aroma, taste, and texture were enhanced despite declining color scores, with no significant difference in overall acceptability between D21 and D28. E-nose principal component analysis (PCA) explained 91.78% total variance and revealed a D21–D28 overlap. HS-GC-IMS detected 84 signal peaks and tentatively identified 75 volatile organic compounds (VOCs). Aldehydes and sulfur-related volatiles generally decreased, whereas esters, ketones, and organic-acid-related compounds accumulated. In total, 33 differential VOCs with variable importance in projection (VIP) > 1 were discriminated during the pickling stage. Correlation analysis revealed associations among physicochemical variables, E-nose responses, and VOC patterns. Results indicate that natural pickling progressively optimizes sensory attributes, reaching a relatively stable aroma state at day 21. This study supplies references for pickling endpoints judgment and supports the processing development of this under exploited vegetable resource.