Comparative Analysis of Hydrosol Volatile Components of Citrus × Aurantium ‘Daidai’ and Citrus × Aurantium L. Dried Buds with Different Extraction Processes Using Headspace-Solid-Phase Microextraction with Gas Chromatography–Mass Spectrometry

This work used headspace solid-phase microextraction with gas chromatography–mass spectrometry (HS-SPME-GC–MS) to analyze the volatile components of hydrosols of Citrus × aurantium ‘Daidai’ and Citrus × aurantium L. dried buds (CAVAs and CADBs) by immersion and ultrasound–microwave synergistic-assisted steam distillation. The results show that a total of 106 volatiles were detected in hydrosols, mainly alcohols, alkenes, and esters, and the high content components of hydrosols were linalool, α-terpineol, and trans-geraniol. In terms of variety, the total and unique components of CAVA hydrosols were much higher than those of CADB hydrosols; the relative contents of 13 components of CAVA hydrosols were greater than those of CADB hydrosols, with geranyl acetate up to 15-fold; all hydrosols had a citrus, floral, and woody aroma. From the pretreatment, more volatile components were retained in the immersion; the relative contents of linalool and α-terpineol were increased by the ultrasound–microwave procedure; and the ultrasound–microwave procedure was favorable for the stimulation of the aroma of CAVA hydrosols, but it diminished the aroma of the CADB hydrosols. This study provides theoretical support for in-depth exploration based on the medicine food homology properties of CAVA and for improving the utilization rate of waste resources.