Abstract
China is a major producer and consumer of green tea and possesses numerous high-quality tea cultivars, which can be used to make green tea. However, the green teas produced from these tea cultivars vary markedly in aroma. In this study, a sensory evaluation method and headspace solid-phase microextraction combined with GC-MS were employed to determine the primary substances that contribute to the aromas and key differences in the aroma components of green tea produced from 20 tea cultivars. The results revealed 57 major volatile components, among which aldehydes, alcohols, and esters were the most prevalent. For the volatile components, the linalool, nonanal, and geraniol contents were the highest, followed by dimethyl sulfide, methyl salicylate, heptanal, and caproicacidhexneylester. The volatile components varied considerably among the green tea samples, and some contained substances with a high content that gave off unique aromas. The correlation analysis revealed significant correlations between the sensory evaluation scores and contents of linalool, geraniol, methyl salicylate, cis-linalool oxide, 3-carene, phenethyl alcohol, limonene, (Z)-3-cis-3-hexenyl isovalerate, citral, (E)-s-ocimene, alcohols, esters, and alkenes, as well as between the sensory evaluation scores and total volatile component contents. Aromatic substances with the highest odor activity values were, in descending order, linalool, capraldehyde, dimethyl sulfide, s-ionone, geraniol, nonanal, heptanal, (E)-2-nonenal, and caproicacidhexneylester. These substances were the major contributors to aroma formation in the green tea samples. The principal component analysis and orthogonal projections to the latent structure-discriminant analysis suggested that the 20 tea cultivars could be grouped into 6 categories and that the high content of linalool, nonanal, and geraniol substantially contributed to the categorization of the tea cultivars. A key variable analysis revealed that 23 volatile components played a critical role in the categorization of the tea cultivars.
Highlights
Camellia sinensis (L.) Kuntze is a perennial woody tea plant that is widely cultivated for the production of a popular nonalcoholic beverage (Wei et al, 2018)
Many methods were used to analyze and compare the green tea aroma characteristics and volatile components to determine the main substances responsible for the aromas and substances that contributed to key aroma differences, such as sensory evaluation, headspace solid-phase microextraction combined with gas chromatographymass spectrometry (HS-SPME-GC-MS), odor active value (OAV), principal component analysis (PCA), and orthogonal projections to latent structure-discriminant analysis (OPLS-DA)
The results indicated a significant correlation between the aroma scores and linalool, geraniol, methyl salicylate, cis-linalool oxide, 3-carene, phenethyl alcohol, limonene, (Z)-3-cis3-hexenyl isovalerate, citral, and (E)-β-ocimene contents
Summary
Camellia sinensis (L.) Kuntze is a perennial woody tea plant that is widely cultivated for the production of a popular nonalcoholic beverage (Wei et al, 2018). The volatile substances (in varying concentration combinations) in tea produce aromas that are sensed by human olfactory nerves. These substances generally account for only 0.01%–0.05% of tea, they are crucial indicators of tea quality (Baba and Kumazawa, 2014; Baldermann et al, 2014). Tea aromas vary based on the different precursor material contents, component ratios, and glycoside hydrolase properties of the corresponding tea cultivars. Various tea cultivars produce various types of tea aromas, each of which is unique to each corresponding tea cultivar (Zhang et al, 2006; Wang et al, 2015; Wang et al, 2016)
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