This research was supported by the National Natural Science Foundation of China (32002094, 32102444), the China Agriculture Research System of MOF and MARA (CARS-19), and the Innovation Project for Chinese Academy of Agricultural Sciences (CAAS-ASTIP-TRI).

1. Preparation of the internal standard and tea infusion
<ol>
	<li>Stock solution: Dissolve 10.0 mg of paraxylene-d10 (see Table of Materials) in 10.0 mL of anhydrous ethanol to prepare a 1,000 ppm stock solution of the internal standard.</li>
	<li>Working solution: Dilute 1 mL of the stock solution (step 1.1) to 100 mL with pure water to prepare a 10 ppm working solution of the internal standard. 
	NOTE: The working solution must be prepared on the same day as the analysis.</li>
...

Unveiling Tea Aroma Complexity with Solvent-Assisted Flavor Evaporation Method

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C., Wei, G., Yang, X., Schieberle, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterisation+of+the+key+aroma+compounds+in+aLongjinggreen+tea+infusion+(Camellia+sinensis)+by+the+sensomics+approach+and+their+quantitative+changes+during+processing+of+the+tea+leaves.">Characterisation of the key aroma compounds in aLongjinggreen tea infusion (Camellia sinensis) by the sensomics approach and their quantitative changes during processing of the tea leaves.</a> European Food Research and Technology. 246 (12), 2411-2425 (2020).</li><li>Feng, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tea+aroma+formation+from+six+model+manufacturing+processes.">Tea aroma formation from six model manufacturing processes.</a> Food Chemistry. 285, 347-354 (2019).</li><li>Wang, J. -. Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+baking+treatment+on+the+sensory+quality+and+physicochemical+properties+of+green+tea+with+different+processing+methods.">Effects of baking treatment on the sensory quality and physicochemical properties of green tea with different processing methods.</a> Food Chemistry. 380, 132217 (2022).</li><li>Zhai, X., Zhang, L., Granvogl, M., Ho, C. -. T., Wan, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flavor+of+tea+(Camellia+sinensis):+A+review+on+odorants+and+analytical+techniques.">Flavor of tea (Camellia sinensis): A review on odorants and analytical techniques.</a> Comprehensive Reviews in Food Science and Food Safety. 21 (5), 3867-3909 (2022).</li><li>Chaturvedula, V. S. P., Prakash, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+aroma,+taste,+color+and+bioactive+constituents+of+tea.">The aroma, taste, color and bioactive constituents of tea.</a> Journal of Medicinal Plants Research. 5 (11), 2110-2124 (2011).</li><li>Ridgway, K., Lalljie, S. P. D., Smith, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sample+preparation+techniques+for+the+determination+of+trace+residues+and+contaminants+in+foods.">Sample preparation techniques for the determination of trace residues and contaminants in foods.</a> Journal of Chromatography A. 1153 (1-2), 36-53 (2007).</li><li>Engel, W., Bahr, W., Schieberle, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solvent+assisted+flavour+evaporation+-+A+new+and+versatile+technique+for+the+careful+and+direct+isolation+of+aroma+compounds+from+complex+food+matrices.">Solvent assisted flavour evaporation - A new and versatile technique for the careful and direct isolation of aroma compounds from complex food matrices.</a> European Food Research and Technology. 209 (3-4), 237-241 (1999).</li><li>Wang, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+aroma+compounds+of+Pu-erh+ripen+tea+using+solvent+assisted+flavor+evaporation+coupled+with+gas+chromatography-mass+spectrometry+and+gas+chromatography-olfactometry.">Characterization of aroma compounds of Pu-erh ripen tea using solvent assisted flavor evaporation coupled with gas chromatography-mass spectrometry and gas chromatography-olfactometry.</a> Food Science and Human Wellness. 11 (3), 618-626 (2022).</li><li>Zou, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zijuan+tea-+based+kombucha:+Physicochemical,+sensorial,+and+antioxidant+profile.">Zijuan tea- based kombucha: Physicochemical, sensorial, and antioxidant profile.</a> Food Chemistry. 363, 130322 (2021).</li><li>Vandendool, H., Kratz, P. 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Part I: Comparison of headspace-solid phase microextraction and solvent assisted flavour evaporation.</a> Lwt-Food Science and Technology. 94, 178-189 (2018).</li><li>Li, Z. W., Wang, J. 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This article describes an efficient method for analyzing volatile compounds in tea infusions using SAFE and GC-MS analysis.
Tea infusions have a complex matrix with a high content of non-volatile components. Several methods have been described in the literature for isolating the volatile components from tea infusions. A common method is simultaneous distillation extraction (SDE)15,16. However, it is not suitable for the analysis of tea...

Tea is a preferred beverage of many people all over the world1,2. The aroma of the tea is a quality criterion as well as a price-determining factor for tea leaves3,4. Thus, the analysis of the aroma composition and content of tea is of great significance for molecular sensory studies and the quality control of tea. As a result, aroma composition analysis has been an important topic in tea research in recent years5,6,7.
The content of aroma components in tea is very low, as they generally only account for 0.01%-0.05% of the dry weight of the tea leaves8. Furthermore, the large amount of non-volatile components in the sample matrix significantly interferes with analysis by gas chromatography9,10. Therefore, a sample preparation procedure is essential to isolate the volatile compounds in tea. The key consideration for the isolation and enrichment method is minimizing the matrix interference and, at the same time, maximizing the preservation of the original odor profile of the sample.
Solvent-assisted flavor evaporation (SAFE), originally developed by Engel, Bahr, and Schieberle, is an improved high-vacuum distillation technique used to isolate volatile compounds from complex food matrixes11,12. A compact glass assembly connected to a high-vacuum pump (under a typical operating pressure of 5 x 10&#8722;3 Pa) can efficiently collect volatile compounds from solvent extracts, oily foods, and aqueous samples.
This article described a method that combines the SAFE technique with solvent extraction to isolate volatile substances from a black tea infusion, followed by analysis using GC-MS.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Alkane mix (C10-C25)</td>
			<td>ANPEL</td>
			<td>CDAA-M-690035</td>
			<td></td>
		</tr>
		<tr>
			<td>Alkane mix (C5-C10)</td>
			<td>ANPEL</td>
			<td>CDAA-M-690037</td>
			<td></td>
		</tr>
		<tr>
			<td>AMDIS</td>
			<td>National Institute of Standards and Technology</td>
			<td>version 2.72</td>
			<td>Gaithersburg, MD</td>
		</tr>
		<tr>
			<td>Analytical balance</td>
			<td>OHAUS</td>
			<td>EX125DH</td>
			<td></td>
		</tr>
		<tr>
			<td>Anhydrous ethanol</td>
			<td>Sinopharm</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Anhydrous sodium sulfate</td>
			<td>aladdin</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Black tea</td>
			<td>Qianhe Tea</td>
			<td></td>
			<td>Huangshan, Anhui province, China</td>
		</tr>
		<tr>
			<td>Concentrator</td>
			<td>Biotage</td>
			<td>TurboVap</td>
			<td></td>
		</tr>
		<tr>
			<td>Data processor</td>
			<td>Agilent</td>
			<td>MassHunter</td>
			<td></td>
		</tr>
		<tr>
			<td>Dichloromethane</td>
			<td>TEDIA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>GC</td>
			<td>Agilent</td>
			<td>7890B</td>
			<td></td>
		</tr>
		<tr>
			<td>GC column</td>
			<td>Agilent</td>
			<td>DB-5MS</td>
			<td></td>
		</tr>
		<tr>
			<td>Green tea</td>
			<td>Qianhe Tea</td>
			<td></td>
			<td>Huangshan, Anhui province, China</td>
		</tr>
		<tr>
			<td>MS</td>
			<td>Agilent</td>
			<td>5977B</td>
			<td></td>
		</tr>
		<tr>
			<td>p-Xylene-d10</td>
			<td>Sigma-Aldrich</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>SAFE</td>
			<td>Glasbl&#228;serei Bahr</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ultra-pure deionized water</td>
			<td>Milipore</td>
			<td>Milli-Q</td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum pump</td>
			<td>Edwards</td>
			<td>T-Station 85H</td>
			<td></td>
		</tr>
	</tbody>
</table>

tea aroma analysis based on solvent-assisted flavor evaporation enrichment

Tea aroma is an important factor in tea quality, but it is challenging to analyze due to the complexity, low concentration, diversity, and lability of the volatile components of tea extract. This study presents a method for obtaining and analyzing the volatile components of tea extract with odor preservation using solvent-assisted flavor evaporation (SAFE) and solvent extraction followed by gas chromatography-mass spectrometry (GC-MS). SAFE is a high-vacuum distillation technique that can isolate volatile compounds from complex food matrices without any non-volatile interference. A complete step-by-step procedure for tea aroma analysis is presented in this article, including the tea infusion preparation, solvent extraction, SAFE distillation, extract concentration, and analysis by GC-MS. This procedure was applied to two tea samples (green tea and black tea), and qualitative as well as quantitative results on the volatile composition of the tea samples were obtained. This method can not only be used for the aroma analysis of various types of tea samples but also for molecular sensory studies on them.

Author Spotlight: Exploring Tea Aroma Using Solvent-Assisted Flavor Evaporation Technique 

Tea Aroma Analysis Based on Solvent-Assisted Flavor Evaporation Enrichment

We explore the molecular basis of taste and aroma, focusing on tea products derived from the Camellia sinensis plant. Our aim is to characterize the flavor molecules and investigate the biochemical processes affecting the sensory attributes of tea. Analyzing tea aroma requires the separation and enrichment of volatiles present in very low concentrations from the complex matrix of tea samples.The sample preparation method often poses the most significant challenge, and it's critical for obtaining valid data, leading to meaningful research conclusions. Through our systematic study on aroma formation, we successfully identified the methyl epi-jasmonate as the key compound responsible for the tea's orchid-like aroma. We also characterize the aromas of four different white tea varieties.The SAFE technique, unlike the commonly-used methods for tea aroma preparation, provides a clear volatile distillate from a tea infusion, free of non-volatile compounds. Aroma compounds can be easily enriched through solvent extraction. Mostly importantly, the odor profile of the obtained aroma concentrate closely resembles that of the origin sample.The proposed method can contribute to various research objectives, such as understanding the evolution of aroma from the tea plant to the tea cup, investigating the chemistry of specific molecules that impact the sensory ecology, characterizing tea aroma to guide plant cultivation, process improvement, quality control, and the creation of new flavors.

The analytical procedure described above is illustrated in this section using the example of the aroma analysis of black tea and green tea samples.
A representative GC-MS chromatogram is shown in Figure 3. Figure 3A shows a set of n-alkanes, and Figure 3B shows the profile of an internal standard. The evaluation results for the extracts from the green tea and black tea samples are shown in <strong class="...

Watch this Scientific Journal Video about Exploring Tea Aroma Using Solvent-Assisted Flavor Evaporation Technique at JoVE.com

Presented here is a method for enriching and analyzing the volatile components of tea extracts using solvent-assisted flavor evaporation and solvent extraction followed by gas chromatography-mass spectrometry, which can be applied to all types of tea samples.

Tea aroma is an important factor in tea quality, but it is challenging to analyze due to the complexity, low concentration, diversity, and lability of the ...

tea-aroma-analysis-based-on-solvent-assisted-flavor-evaporation