Identification and characterization of the key volatile flavor compounds in black teas from distinct regions worldwide

Abstract

Volatile flavor compounds in 112 black teas from seven countries were analyzed by untargeted metabolomics using headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME/GC-MS). Multivariate statistical analysis and odor activity values (OAVs) were used to classify these samples and identify key odorants. A total of 140 volatile flavor compounds (VFCs), including 12 different groups, were identified, and alcohols were prevalent in China and India samples, accounting for 40.83% and 34.96% of the total VFCs, respectively. Eight volatile compounds with OAVs > 1 were identified as key active differential odorants in Chinese, Indian, and Sri Lankan samples, including linalool, pentanoic acid, methyl salicylate, hexanoic acid, 1-methyl-naphthalene, phenylethyl alcohol, geraniol, and β-ionone. Linalool, pentanoic acid, and hexanoic acid in Indian black teas, phenylethyl alcohol in Chinese black teas, and 1-methyl-naphthalene, β-ionone in Sri Lankan black teas could be used to discriminate different black tea groups. A total of 12-14 VFCs with OAVs > 1 were identified as key active aromatics in Chinese black tea sample. Linalool and benzeneacetaldehyde in Yingde (Guangdong) black tea, methyl salicylate in Taiwanese samples, and benzeneacetic acid in Anhui black tea could be used as biomarkers to distinguish them from other Chinese samples. Sensory evaluation results showed that most black teas presented the common sweet, floral odors, which were consistent with GC-MS analysis. These results will contribute to characterize the odor metabolome of black teas and provide biochemical basis for identifying the authenticity of different black teas. K E Y W O R D Sblack tea, metabolomics, odor activity value, partial least-squares discriminant analysis, volatile flavor compound Practical Application: Linalool, pentanoic acid, and hexanoic acid in Indian black teas, phenylethyl alcohol in Chinese black teas, 1-methyl-naphthalene, β-ionone, and methyl salicylate in Sri Lankan black teas could be used to discriminate black teas from the three countries. Linalool and benzeneacetaldehyde in

Characterization of the Aroma Profiles of Guangdong Black Teas Using Non-Targeted Metabolomics

“…Floral and sweet aromas are typically attributed to geraniol, β -ionone, linalool, phenylethyl alcohol, benzeneacetaldehyde, and β -damascenone [ 22 ]. Mint- or peppermint-like aromas, exemplified by teas from Renhua, are attributed to methyl salicylate or citral [ 18 , 23 ].…”

“…Among the ketones detected, β -ionone existed in the highest relative concentration in Meizhou black teas (278.91 ng/g). β -Ionone is also an important volatile compound in black and green teas that contributes to the sweet, floral note of tea aromas [ 5 , 18 ].…”

“…As a result of fermentation, acids are often detected in black teas, which affect their overall quality. For example, Indian crush, tear, curl (CTC) black teas, which contain volatile acids such as hexanoic acid and pentanoic acid in high relative concentrations, are generally heavily fermented [ 18 ].…”

“…The extraction of the VFCs and the GC–MS identification procedures employed were identical to those of our previous study [ 18 ]. Briefly, a ground black tea sample (1.5 g) and ethyl decanoate (20 µL, 0.02 mg/mL), as an internal standard, were transferred to a SPME bottle.…”

“…Finally, the volatile compounds were identified according to the retention time, precise molecular mass, mass spectra, and the matching similarity in the public database, the NIST library (accessed on June 2014). The relative concentration of the VFCs was semi-quantified and calculated according to the content and peak area of the ethyl decanoate as follows [ 18 ]: …”