Abstract
The present study aims at the development and validation of a quali-quantitative headspace solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME GC-MS) method for the analysis of odorants in different Chinese and Japanese green teas. A 65 µm PDMS/DVB fiber was used, and GC-MS was performed on a ZB-5 (30 m × 0.25 mm ID, 0.25 μm film) column. The main odorants in green tea samples were identified and the method was fully validated. Linearity (r2 0.981–0.999), sensitivity (LOQ 0.005–0.04 µg/mL), reproducibility (CV% 3.12–10.37), accuracy (recovery% 79.08–99.17) and matrix effect (ME% −9.5 to +4.5) were determined. Quantitation of 2,4-heptadienal, β-damascenone, β-ionone, linalool, indole, 2-ethyl-6-methyl-pyrazine, 2-ethyl-5-methyl-pyrazine, 2-ethyl-3,6-dimethylpirazine, 2-ethyl-3,5-dimethyl-pyrazine and 2-acetyl-pyrazine was carried out in the presence of isotopically labeled compounds as the internal standards. The proposed method was applied to the comparison of the profile of the volatile flavor compounds (VFCs) of green tea subjected to roasting treatment at three different temperatures (160, 180 and 200 °C for 30 min). In particular, the roasting process was monitored by following the quantitative variations of the selected odorant content, considered as the most important contributory components to the Hojicha or black tea (roasted tea) flavor. A temperature of 160 °C was found to be the best roasting temperature.
Highlights
Green tea, the most widely consumed beverage in Asia, has recently become more widespread in the West where black tea is traditionally consumed
The present study aims at the development and validation of a quali-quantitative headspace solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME GC-MS) method for the analysis of odorants in different Chinese and Japanese green teas
The proposed method was applied to the comparison of the profile of the volatile flavor compounds (VFCs) of green tea subjected to roasting treatment at three different temperatures (160, 180 and 200 ◦C for 30 min)
Summary
The most widely consumed beverage in Asia, has recently become more widespread in the West where black tea is traditionally consumed. The manufacturing process of green tea includes steaming, characteristic of most of the Japanese teas, like Sencha, or pan-firing, typical of most of the Chinese teas, i.e., Bancha. During these processes, the oxidase enzyme, present in tea leaves, is inactivated, preserving the green color of the leaves and the catechin composition. The changes in the volatile flavor compound (VFC) profile showed a significant increase in some potent odorants, including pyrazines, the most contributory components of the Hojicha flavor [7,8], and specific variation in characteristic odorants, such as 2,4-heptadienal, β-damascenone, β-ionone, linalool and indole
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