Analysis of Volatile Components in Chrysanthemum nankingense Leaves Dried by Different Methods by Headspace Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry and Calculation of Odor Activity Value

To determine the effects of drying methods on the volatile compounds and explore the key aroma compounds in Chrysanthemum nankingense leaves, head-space solid phase micro-extraction combined with gas chromatography mass spectrometry (HS-SPME-GC-MS) was employed for quantitative and qualitative analysis of the volatile compounds in C. nankingense leaves dried by hot air drying, vacuum-freeze drying or microwave-hot air drying. The result showed that a total of 140 compounds belonging to six classes (terpenes, esters, aldehydes, alcohols, aromatic compounds and other substances) were identified in all samples. Of these, 112, 86, 83 and 85 were detected in fresh and dried C. nankingense obtained by hot air drying, microwave-hot air drying, and vacuum-freeze drying, respectively. Among these compounds, terpenes were the most abundant, with contents of 229474.33, 64629.68, 56469.88 and 70832.87 μg/kg in fresh, hot air dried, microwave-hot air dried, and vacuum-freeze dried samples, respectively. Compared with the other drying methods, vacuum-freeze drying gave better retention of the abundance of volatile compounds. Vacuum-freeze dried C. nankingense had similar flavor to fresh samples, showing camphor-like, turpentine-like, flowery and grassy aromas. GC-MS combined with odor activity values (OAVs) confirmed that β-ocimene, caryophyllene and trans-β-farnesene were the major aroma components. GC-MS combined with E-nose can represent an efficient nondestructive method for the detection of volatile compounds in C. nankingense leaves and allow the discrimination of dried C. nankingense obtained by different drying methods. These results provide a theoretical basis for choosing drying methods and understanding the difference in volatiles components in dried C. nankingense obtained by different drying methods.