The aim of this study was to investigate and evaluate the processing adaptability of Osmanthus fragrans pomace, a by-product of O. fragrans extract, in order to provide a reference for its rational utilization. We examined the physical properties, nutrient composition, antioxidant capacity and tyrosinase inhibitory activity of O. fragrans pomace prepared by vacuum microwave drying (VMD), vacuum freeze drying (VFD), or heat pump drying (HPD). The results showed that the VFD sample had good color with the lowest ΔE and browning index of 14.26 ± 0.53 and 12.43 ± 0.65, respectively, and possessed the highest contents of total phenols and total flavonoids, and exhibited the highest water-holding capacity and antioxidant capacity. The VMD sample possessed the highest contents of soluble dietary fiber, total phenylethanol glycosides, actecoside, and salidroside, and exhibited the strongest oil-holding capacity and tyrosinase inhibitory activity. Pearson correlation analysis showed that the antioxidant capacity was significantly and positively correlated with the contents of total phenols and total flavonoids, and the tyrosinase inhibitory activity was significantly and positively correlated with the contents of total phenylethanol glycosides, total sugars, and total tannins. Partial least squares-discriminant analysis (PLS-DA) could distinguish differently dried O. fragrans pomace and the proposed model was stable with good predictability. According to Topsis analysis, the VFD sample had the best quality, and the VMD sample was superior to the HPD sample. In conclusion, O. fragrans pomace has good physical properties, nutrient composition, antioxidant capacity, and tyrosinase inhibitory activity, thereby holding potential as a raw material for functional food and whitening cosmetics. This study provides a reference for the application of differently dried O. fragrans pomace.

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.

This study analyzed and compared the effects of different drying methods on the volatile composition and aroma characteristics of Osmanthus fragrans extract and absolute oil. The volatile composition was determined by gas chromatography-mass spectrometry (GC-MS) and partial least squares-discriminant analysis (PLS-DA), relative odor activity value (ROAV), aroma profile radar and principal component analysis (PCA) were employed to determine the effect of different drying methods on the volatile aroma components of O. fragrans extract and absolute oil. The results showed that a total of 113 volatile components were identified. The types and concentrations of volatile components were significantly different among samples (P < 0.05). Through PLS-DA analysis, 36 volatile marker substances were selected using the cutoff of variable importance in the projection (VIP) score greater than 1, and the accuracy of predictive discrimination of O. fragrans extract and absolute oil prepared by different drying methods was 99.6%. The ROAV and aroma radar plots showed that dihydro-β-ionone, linalool, nonanal, β-ionone, and dihydro-β-iononeone contributed significantly to the aroma of O. fragrans extract and absolute oil, being responsible for the floral, woody, and fruity aromas. Notably, the extract from freeze-dried O. fragrans exhibited a more intense aroma. PCA analysis indicated that freeze-drying contributed to improving the aroma quality of O. fragrans extract and absolute oil. The results of this study provide theoretical support for process optimization and quality improvement of O. fragrans extract products.