Association between lipid oxidation and volatile profile evolution during stir-frying of Gardeniae Fructus Praeparatus.

The dynamic evolution of volatile compounds during the stir-frying of Gardeniae Fructus Praeparatus (GFP) and its association with lipid oxidation were systematically investigated using an integrated approach combining electronic nose, headspace solid-phase microextraction coupled with gas chromatography-quadrupole time-of-flight mass spectrometry, gas chromatography-olfactometry, and online recombination/omission models. A total of 149 volatile compounds were identified across five processing stages, revealing a progressive transformation from alcohol/terpenoid-dominated profiles in Gardeniae Fructus to heterocycle/ketone/phenol-dominated profiles in GFP. Heterocyclic compounds, particularly pyrazines and 2-acetylpyrrole, markedly increased in GFP, while phenolic compounds predominantly accumulated during the over-processed stage. There was a progressive increase in lipid oxidation indices, including diene, carbonyl, and p-anisidine values. This was accompanied by a significant decline in unsaturated fatty acids (oleic, linoleic, and α-linolenic acid), indicating a progressive intensification of lipid oxidation with processing severity. Partial least squares regression and Spearman correlation analyses established a robust association between lipid oxidation parameters and key volatile compounds (R2X = 0.996, R2Y = 0.982, Q2 = 0.963), indicating that the degradation of unsaturated fatty acids and subsequent secondary oxidation products are closely associated with the formation of characteristic burnt aroma. Gas chromatography-olfactometry combined with recombination and omission experiments further identified 32 key aroma-active compounds, among which 2,3,5-trimethylpyrazine, 3-ethyl-2,5-dimethylpyrazine, furfural, 2-furanmethanol, and guaiacol are suggested as the characteristic contributors to the burnt aroma of GFP. Collectively, these findings suggest that lipid oxidation is closely correlated with the formation of the burnt aroma of GFP, acting synergistically with Maillard and caramelization reactions to shape the final volatile profile. This study provides a comprehensive volatile basis for elucidating the chemical mechanisms underlying burnt arom formation and identifies objective chemical markers for determining the optimal processing endpoint.