🍵 TL;DR: Tea first or water first? Jump straight to the conclusion 🎯

Based on the SCI paper published by Sun Shihao's team in 《Current Research in Food Science》, you can directly find the corresponding option according to your own taste preferences:

• 🌸 If you want to drink high-aroma and elegant green tea (such as Biluochun), use the top-down method (pour water first, then add tea): First pour 80°C hot water to 70% full, then add tea. Note to appropriately shorten the steeping time to reduce bitterness.

• 🌰 If you want to drink green tea with a mellow chestnut aroma (such as Liuan Guapian), use the bottom-up method (put the tea first, then pour water): Put the tea first, then pour in hot water at 85–90°C, and steep for 1–2 minutes.

• ⚖️ Medium-tender green tea (such as Longjing) → You can try the middle-pouring method: First pour 1/3 of the water, add the tea leaves and shake to release the aroma, then top up to 70% full to balance both aroma and taste.

📝 Summary in one sentence: The top-down method produces high aroma but is slightly bitter, the bottom-up method is mellow with prominent chestnut aroma, and the middle-down method is a compromise. Below, we will break down the scientific basis behind it in detail for you.

📖 Introduction: A Neglected Issue of Tea Brewing Sequence

When brewing green tea, do you first add tea leaves and then pour water (bottom-up method), or first pour water and then add tea leaves (top-down method)?

To most people, this is just an insignificant habit. However, the research team led by Researcher Sun Shihao from the China National Research Institute of Food and Fermentation Industries, published in the renowned food science journal 《Current Research in Food Science》, for the first time confirmed at the molecular level that: the differences in aroma and taste between green tea brewed by adding tea first and adding tea later far exceed your imagination.

• 📄 Paper Title: Revealing the influence of top-brewing and bottom-brewing methods on the flavor of green tea based on the interaction between EGCG and aroma compounds

• 🔬 Research Object: Anhui Famous and High-quality Green Tea "Shucheng Xiaolan Flower"

• 💡 Key Findings: The flavor difference between the top-down and bottom-up brewing methods stems from the intermolecular interaction mechanism between EGCG (epigallocatechin gallate) and aroma compounds.

🥄 Two Brewing Methods, with Vast Differences in Definition and Sensory Experience

1. Comparison of operations between the two brewing methods

Table 1 – Operational Definitions of the Top-Down Method and the Bottom-Up Method

📌 Data source: Sun Shihao, Current Research in Food Science, 2026

2. Sensory Evaluation Results: A Trade-off Concerning Choice

The research team adopted quantitative descriptive analysis, and professional sensory evaluation personnel scored the tea soup of the two brewing methods. The results are clear:

• 🌸 Top-pouring method: The intensity of the delicate fragrance and floral aroma is significantly higher, and the tea soup is fresh and elegant, but the bitter and astringent taste is also more prominent.

• 🌰 Downward Pouring Method: Chestnut aroma is extremely prominent, the tea soup is mellow and gentle, bitterness and astringency are significantly alleviated.

Comparison of Sensory Characteristics of Tea Infusions between Top Brewing Method and Bottom Brewing Method

🎯 Core Conclusion: If you pursue high fragrance and elegance → choose the upper-pouring method; if you prefer mellow chestnut fragrance → choose the lower-pouring method.

🔬 Ingredient Decryption: Why does the top-pouring method result in a more fragrant but also more bitter taste?

1. Aroma Components: The top-down brewing method releases more key aromas

Using HS-SPME-GC-MS technology, a total of 92 volatile aroma compounds were identified through research. The analysis revealed that:

• In the tea liquor prepared by the top-down method (85°C), the contents of key aroma compounds such as geraniol, nonanal, and methyl salicylate are significantly higher than those in the bottom-up method.

• Through orthogonal partial least squares discriminant analysis (OPLS-DA), these compounds were identified as markers to distinguish between the two brewing methods.

• The total odor activity value (OAV) of the top-pouring method reaches its maximum at 85°C, which explains why its aroma performance is more prominent.

 Interaction between EGCG and characteristic aroma compounds

📝 Summary: The top-down brewing method has a higher EGCG content, which "captures" floral aroma substances (such as geraniol and α-ionone) more tightly and releases them only when drinking, so the floral aroma is more pronounced. The bottom-up brewing method has relatively less EGCG, failing to capture as much floral aroma, instead making chestnut aroma substances more prominent. In addition, compounds such as geraniol, nonanal, and methyl salicylate may be the main chemical components responsible for the differences in aroma characteristics.

2. Polyphenol components: The top-pouring method dissolves more EGCG, resulting in bitterness

Using UHPLC-Q-Exactive MS to analyze polyphenolic compounds:

• The total polyphenol content in the tea soup of the upcasting method was significantly higher than that of the downcasting method, among which EGCG (the main bitter component of tea polyphenols) accounted for the highest proportion.

• This is precisely the direct chemical reason why the top-down method results in a stronger bitter taste while the bottom-up method yields a smoother flavor.

 Comparison of Tea Polyphenols in Two Brewing Methods

📝 Summary: The top-pouring method releases more tea polyphenols while releasing aroma – the coexistence of high aroma and high bitterness is an inseparable trade-off.

🔗 Molecular Mechanism: The "Secret Handshake" between EGCG and Aroma Compounds

Finding compositional differences is not enough. The team led by Sun Shihao further employed ultraviolet-visible spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, and proton nuclear magnetic resonance spectroscopy, combined with Density functional theory (DFT) calculations, to reveal the underlying molecular mechanism.

1. Interaction type

Table 2 – Non-covalent interactions between EGCG and aroma compounds

2. Key Findings: EGCG Inhibits Aroma Volatilization

Research confirms:

• EGCG has a significant inhibitory effect on the volatilization of aroma compounds. It forms non-covalent complexes with aroma molecules through hydrogen bonding, π-π stacking, and hydrophobic interactions, altering the retention and release behavior of aroma in tea infusion.

• The different functional group structures of various aroma compounds lead to differences in their selective binding with EGCG. This ultimately shapes the distinct flavor profiles of the top-down and bottom-up brewing methods.

3. Research Flowchart: The Complete Logic from Brewing Methods to Flavor Differences

Figure 1 – Research Logic Flowchart

Figure caption: Different brewing methods result in different amounts of EGCG dissolution, and EGCG ultimately determines the flavor performance of tea soup through selective binding with aroma molecules.

🌍 Extended Research: The Broader Impact of Brewing Parameters on Flavor

The research of Sun Shihao's team is not an isolated case. The impact of brewing conditions (sequence, temperature, time, water-to-tea ratio) on the flavor of tea soup has become a research hotspot in the field of food science.

1. Support for review papers

Associate Professor Chen Ping from Zhejiang University and Anhui Agricultural University Professor Song Chuankui published a review in 《Trends in Food Science & Technology》 that pointed out:

• Brewing temperature, time, and water-to-tea ratio have a significant impact on the leaching and transformation of chemical components in tea leaves.

• Different types of tea require specific brewing parameters to achieve the best flavor.

2. Other EGCG-Aroma Interaction Studies

• Study on Aroma Compounds in Longjing Green Tea Beverage and Their Interactions with the Matrix
  Yongcheng Liao from Huazhong Agricultural University in his doctoral dissertation "Aroma Compounds in Longjing Green Tea Beverage and Their Interactions with the Matrix" used one-dimensional/two-dimensional nuclear magnetic resonance spectroscopy (1D/2D NMR) and quantitative structure-activity relationship (QSAR) models, and through the study of Longjing green tea beverage, confirmed that EGCG binds to aroma compounds through hydrogen bonds and π bonds, and successfully established a prediction model for aroma release.

• Crystallographic Study of the Complex of Catechin and Caffeine
  Dong Yanru, Cao Yanyan et al. published in 《Journal of Tea Science》 Crystallographic Study of Catechin-Caffeine Complexes, which found through crystallographic analysis and high-performance liquid chromatography (HPLC) that catechins and caffeine mainly form non-covalent complexes with a stoichiometric ratio of 1:1 or 2:2 through hydrogen bonding and face-to-face π-π stacking interactions.

• Study on the Inhibition of EGCG on the "Mature Flavor" of Green Tea
  《Food Chemistry》 published an article titled 《Volatolomics-assisted characterization of the key odorants in green off-flavor black tea and their dynamic changes during processing》 in 2024, which proposed that EGCG can effectively inhibit the formation of volatile sulfur compounds that cause the "cooked off-flavor" in green tea by forming adducts with glucose and methional, namely, the inhibition of the "cooked flavor" in green tea.

🔗These studies together support a conclusion: the non-covalent interaction between polyphenols and aroma is the key molecular mechanism determining the final flavor of tea soup. 

🎓 Conclusion: The Chemical Code of a Good Cup of Tea

The research of Sun Shihao's team not only validates the wisdom of traditional tea art but also reveals its underlying mechanism using modern instruments and molecular simulations – hydrogen bonds, π-π stacking, and hydrophobic interactions between EGCG and aroma compounds, which form a delicate regulatory network in the microscopic world.

🍃 Next time you make tea, you may realize that every moment when the tea leaves slowly sink in the cup or are instantly hit by hot water is a precise chemical experiment on aroma. And your choice of "tea first or water first" is essentially an active intervention in the direction of intermolecular interactions.

📚 Summary of Core Literature Sources

1. 《Revealing the influence of top-brewing and bottom-brewing methods on the flavor of green tea based on the interaction between EGCG and aroma compounds》, Sun, S. et al. 《Current Research in Food Science》

2. 《Advancement and challenges in tea brewing: The dynamic principles, influencing factors, innovative processing technologies and pollutants》, Chen, P. & Song, C. K., 《Trends in Food Science & Technology》

3. 《Research on the Complex of Catechins and Caffeine》, Dong Yanru, Cao Yanyan, 《Journal of Tea Science》

4. Aroma Compounds in Longjing Green Tea Beverage and Their Interactions with the Matrix, Liao Yongcheng

5. 《Volatolomics-assisted characterization of the key odorants in green off-flavor black tea and their dynamic changes during processing》, Yanqin Yang, Jialing Xie, Qiwei Wang, Lilei Wang, Yan Shang, Yongwen Jiang, Haibo Yuan; 《Food Chemistry》

☕ Science meets tradition: one cup, one molecular masterpiece.