Impact of Membrane Separation Refining on Volatile Organic Compounds of Osmanthus fragrans Absolute Oil Analyzed Using Gas Chromatography-Mass Spectrometry Combined with Odor Activity Value

In order to investigate the difference in aroma quality among Osmanthus fragrans absolute oil and the permeate and retenate obtained from its membrane separation, a total of 66 volatile organic compounds (VOCs) were detected in the samples by gas chromatography-mass spectrometry (GC-MS). Statistical analysis revealed significant difference in both the types and concentrations of VOCs among different samples (P < 0.05). The application of orthogonal partial least squares-discriminant analysis (OPLS-DA) successfully discriminated the three samples, with a predictive accuracy of 93.6%. In addition, 10 differential compounds were selected using variable important in the projection (VIP) value > 1 as the cutoff, and clustering heatmap analysis identified 9, 3 and 1 major VOCs in the oil, retenate and permeate, respectively. The permeate exhibited good anti-flocculation properties and a stable rheological tend, containing the lowest contents of palmitic acid and its derivatives. The absolute oil exhibited the most prominent floral, fruity, greasy and cologne-like aromas with odor activity value (OAV) of 1371871.65, 41885.15, 37199.21 and 3050.71, respectively, whereas the permeate showed the most intense herbaceous aroma with OAV of 3241379.60. The results from the present study will provide a theoretical basis for the application of membrane separation to the purification of O. fragrans absolute oil and for the evaluation of the characteristic aroma of the oil and its fractions.