Optimization of Solid Phase Microextraction (SPME) Coupled with Gas Chromatography Mass Spectrometry (GC-MS) for Fermented Perilla Leaves Jiaosu and Volatile Profiling Analysis During Fermentation

A method based on solid phase microextraction coupled with gas chromatography mass spectrometry was developed for volatile profiling fermented perilla leaves jiaosu (PFJ) during fermentation. Five fibers were firstly evaluated by the total peak areas and the number of volatile compounds. Secondly, a Plackett-Burman design was applied to screen for seven independent variables selected in literature. Three significant variables (extraction time, extraction temperature and equilibrium time) were therefore selected for the following optimization studies. A Box-Behnken design combined with a steepest ascent was then used to optimize the significant factors. Under optimal conditions, the changes of volatile profiles of PFJ at 7, 14, 21, 28, 91 and 140 d were analyzed. A total of fifty-one volatile compounds were identified, and alcohols (68.12–78.94%) were the main volatile components in PFJ, followed by methoxy-phenolic compounds (4.67–5.48%). Perilla alcohol and trans-Shisool were the major constituents during spontaneous fermentation, which accounted for 16.14–30.66% and 19.95–24.52%, respectively. The results showed that PFJ fermented into a health probiotic product with characteristic flavour and functional volatile compounds.