Dynamic Headspace Combined with Gas Chromatography-Olfactometry-Mass Spectrometry for Analysis of Volatile Components in Baked Green Tea from Different Cultivars

In this study, a dynamic headspace (DHS) combined with thermal desorption/gas chromatography-mass spectrometry (TD/GC-MS) method was established to analyze the volatile composition of baked green tea. Extraction parameters including tea amount, trapping temperature, incubation temperature, total purge volume, purge rate, and drying rate were optimized. Furthermore, the key odorants of baked green tea made from different tea cultivars were identified by gas chromatography-olfactometry-mass spectrometry (GC-O-MS). The results indicated that the optimal extraction conditions were as follows: tea amount of 200 mg, trapping temperature of 70 ℃, incubation temperature of 70 ℃, total purge volume of 350 mL, purge rate of 10 mL/min, and drying rate of 10 mL/min. A total of 74 volatile components were identified in green tea made from three representative varieties. Multivariate statistical analysis showed that the aroma compounds of the three green teas varied greatly, and 18 key differential volatile aroma components were identified. The contents of isopropylidesneacetone and linalool in LongJing 43 (LJ 43) baked green tea were the highest among these three teas. Fuding Dabaicha (FDDB) baked green tea contained the highest levels of 6-methyl-5-heptene-2-one, octanal, cyclohexanone, acetophenone, copaene and epicubenol. A total of 28 odorants were identified by GC-O-MS analysis. The odorants were mainly responsible for odor attributes such as green, refreshing, floral, fruity, herbal, woody and sweet aromas. The total aroma intensity of floral and fruity attributes was the highest, followed by the green and refreshing attributes. Taken collectively, linalool, calamenene, δ-cadinene, 6-methyl-5-heptene-2-one and octanal were the key differential odorants among the three green teas. Linalool contributed significantly to LJ 43 baked green tea, and the other four odorants contributed significantly to the formation of the aroma quality of FDDB baked green tea.