Evaluation of the recent seasonal variations of the composition and enantiomeric distribution of volatiles and of polymethoxyflavone in Sicilian cold-pressed mandarin (C. deliciosa Ten.)

Cold-pressed mandarin (Citrus deliciosa Ten.) essential oil is prized for its aroma and bioactive properties, yet its composition varies seasonally. This study assessed the volatile profile, enantiomeric distribution, and polymethoxyflavone (PMF) content of Sicilian mandarin oils across different harvests. A total of 111 samples were collected over three consecutive seasons (2020–2024) in Sicily. Volatile compounds were analyzed using gas chromatography coupled to mass spectrometer (GC–MS) for identification and flame ionization detector (GC–FID) for quantification. Enantiomeric ratios of selected chiral monoterpenes were determined via dual-detection enantioselective GC–(FID)₂, improving separation of critical pairs. PMF content was measured by HPLC-PDA. Results revealed significant seasonal variation in volatile and PMF profiles, highlighting the influence of harvest timing on oil quality. Enantiomeric ratios also varied, confirming their role as reliable quality indicators.