Rapid Monitoring of Storage Deterioration in Processed Coix Seeds Using Near-Infrared Spectroscopy Guided by GC–IMS

Processed coix seeds are widely consumed as both food and traditional medicinal materials, but their quality gradually deteriorates during storage due to lipid oxidation and rancid odor formation. In this study, volatile changes during storage were characterized using gas chromatography–ion mobility spectrometry (GC–IMS), and a rapid monitoring method based on near-infrared spectroscopy (NIRS) was developed. GC–IMS identified 74 volatile compounds, with aldehydes and ketones increasing significantly during storage, indicating progressive lipid oxidation. Key markers, including 2-furaldehyde, 1-pentanoic acid, and γ-caprolactone, were identified as indicators of quality deterioration. Based on these markers, composite flavor and storage deterioration indices were constructed and used as reference parameters for NIRS calibration. Partial least squares regression models developed in the 1300–2500 nm region showed strong predictive performance for these composite indices, with R2p > 0.93 and RPD > 4.0. The long-wave NIR region exhibited superior sensitivity to oxidation-related spectral changes. These results demonstrate that NIRS combined with GC–IMS analysis provides an effective, chemically interpretable approach for rapid, non-destructive monitoring of storage quality in processed coix seeds.