Chemometric Identification of Volatile Components in Essential Oils Extracted from Sweet Orange Peels by Different Methods

Quantitative descriptive sensory analysis (QDSA), gas chromatography-ion mobility spectrometry (GC-IMS) and Heracles NEO electronic nose (E-nose) combined with chemometrics were used for differential analysis of volatile compounds in essential oils (EOs) extracted from sweet orange peels (blood and navel) using cold pressing (CP), microwave-assisted hydrodistillation (MAHD) or spinning cone column (SCC). The results indicated that significant variations in flavor composition were found among the three EOs. The CP oil had the highest sensory preference with stronger fruity, sweet, and floral aromas. The MAHD oil had stronger fatty, green, and woody aromas, and the SCC oil had a lower aroma intensity. A total of 64 volatile components were identified by GC-IMS, terpenes, alcohols and aldehydes being the major ones, followed by acids, esters and other compounds. The fingerprint indicated that the contents of terpenes in the CP and MAHD oils were significantly higher than that in the SCC oil, whereas the contents of alcohols and aldehydes in the MAHD and SCC oils were significantly higher than those in the CP oil. Based on relative odor activity value (ROAV), β-myrcene and linalool were identified as the major contributors to the flavor of sweet orange EO. Moreover, using GC-IMS combined with partial least square discriminant analysis (PLS-DA) and variable importance in the projection (VIP), 13 differential volatile compounds were identified as aroma markers to distinguish among the 6 oils. Additionally, E-nose combined with principal component analysis (PCA) and discriminant factor analysis (DFA) also successfully distinguished among the 6 EOs according to their volatile compounds.