The Tea That Holds Its Breath: How GABA Oolong Is Made

Tea Science｜Author：祥興茶行｜Published：2026-07-15

Seal freshly plucked tea leaves away from oxygen and they flood themselves with GABA — the trick behind Gabaron tea. From a 1987 Japanese lab bench to Taiwan's floral GABA oolong, here is the process, the flavor, and an honest look at the health evidence.

There is a tea in this world made by deliberately taking the breath away from freshly plucked leaves. Shut tender leaves inside an oxygen-free environment for a few hours and, to survive the stress, they accumulate massive amounts of an amino acid called GABA (γ-aminobutyric acid) — as much as 187 mg per 100 g of dry tea [8]. That is how the tea earned its name: Gabaron tea (佳葉龍茶). How is it made? What does it taste like? And how was it invented, improved, and studied into what it is today? This piece walks you through all of it.

Meet GABA first GABA (γ-aminobutyric acid) is an amino acid found naturally in plants and in the human body — think of it as an emergency compound the leaf rushes to manufacture when starved of oxygen. What defines Gabaron tea is a special process that pushes this compound to very high levels (the common commercial threshold is ≥150 mg per 100 g of dry tea [8]).

〔圖〕GABA γ-胺基丁酸 分子結構式

GABA (γ-aminobutyric acid)

Oxygen deprivation activates glutamate decarboxylase (GAD), which clips a carboxyl group off glutamate — and out comes GABA.

How It Is Made

The most captivating thing about Gabaron tea is that the process itself reads like a science story.

Everything starts in 1987. A team led by Tojiro Tsushida at Japan's Tea Experiment Station (later absorbed into NARO, the national agricultural research organization) published a remarkably clean method: fresh shoots of the Yabukita cultivar — one bud and three leaves — went into flasks flushed continuously with oxygen-free nitrogen, then sat at 25°C in complete darkness for several hours [1]. Cutting off the oxygen switches on an enzyme in the leaf called glutamate decarboxylase, or GAD — picture it as the leaf's built-in processing machine, whose one job is to clip a small piece off a raw material called glutamate, turning it into GABA. Just like that, within a few hours, GABA piles up inside the leaf.

A detail that keeps getting written wrong: the original invention used nitrogen gas only — not the carbon dioxide or vacuum treatments so often described [1]. CO₂ and vacuum packing are variants developed later for commercial production. The 1987 experiment was in fact strikingly simple: the only difference between the aerobic and anaerobic groups was whether nitrogen was flushed through, with everything else identical — which made the control unusually rigorous.

By the time the tea reached commercial production, the process had evolved into a more deliberate alternating anaerobic–aerobic sequence. Taiwan's recent GABA oolongs, for example, use two aerobic rolling stages interleaved with three anaerobic fermentation stages, run in alternation [11]. Aerobic rolling breaks open the leaf cells and readies the raw material; the anaerobic stages then let GAD produce GABA at full tilt. Repeat the cycle, and GABA climbs steadily higher. Here is roughly what the production line looks like:

```mermaid flowchart LR A[Pluck fresh leaves] --> B[Aerobic rolling breaks cell walls] B --> C[Anaerobic fermentation nitrogen flush, GAD makes GABA] C --> D[More aerobic, more anaerobic alternating cycles accumulate GABA] D --> E[Kill-green fixation] E --> F[Dry into finished tea] ```

The step that made Gabaron tea genuinely delicious in Taiwan, though, was a local re-engineering by the Tea Research and Extension Station (TRES). GABA tea originated in Japan, where the original method used green tea, steam-fixed without withering — and the residual chlorophyll tended to leave a grassy off-note. TRES sent staff to Japan in 1994 to learn the key technique, began promoting the tea domestically in 2004, and made one clever pivot: it switched to oolong styles (Wenshan Baozhong, high-mountain tea, Dong Ding oolong, Oriental Beauty), taking a route of heavy withering, heavy tumbling, and heavy oxidation [12]. That single change stripped out the stuffy, sour notes of the traditional anaerobic process while keeping GABA levels high — producing Taiwan's own signature "GABA oolong."

The Taste: Gently Tart and Sweet, Floral, With a Returning Sweetness

With the process covered, the most practical question follows: is this tea actually good?

Early traditional Gabaron tea did go through an awkward phase. Anaerobic fermentation produces organic acids, and combined with the residual chlorophyll of the original method, the tea could easily come out sour, grassy, even carrying a harsh "fire" note [11][12]. That was exactly what motivated TRES's oolong-based redesign.

The flavor picture of the improved GABA oolong is far more flattering. A sensory study of young Taiwanese consumers dissected the taste of cold-brewed GABA oolong and identified as many as 13 well-liked flavor attributes — including sweet aroma, floral notes, honeyed aroma, fruitiness, brisk freshness, a returning sweetness in the finish (hui gan), a long-lingering aftertaste, a silky mouthfeel, and a cooling quality [11]. The study's overall verdict: gently tart with sweetness, savory-fresh, clean, and distinctly floral — and after the redesign, those troublesome fire and sour notes "no longer appear" [11].

Where does the aroma come from? Using GC-MS (an instrument that unpacks an aroma into its individual chemical molecules), researchers traced the fresh floral-fruity character of Gabaron tea to volatiles such as geraniol (a rose-like floral note) and linalool (carrying a citrus-blossom character) [13]. A 2024 multi-omics study went further, revealing for the first time that anaerobic treatment chiefly affects lipid- and glycoside-derived volatiles, with a transcription factor called CsERF involved in regulating aroma formation [13]. In other words, the florality is not an additive — the process rewires the leaf's own aroma-making pathways.

Set against the teas most people know: it is neither as light and direct as green tea nor as heavy as a dark-roast oolong. It walks a fresher line — lifted florals with a gentle tartness and a returning sweetness — and it is especially charming cold-brewed.

How the Research on One Tea Grew Up

Gabaron tea makes an unusually good case study in how a single line of research accumulates into a body of knowledge. Its story spans nearly 40 years, from an invention in Japan, to localization in Taiwan, to modern molecular-level analysis:

1987 · The invention Tojiro Tsushida's team in Japan publishes the anaerobic GABA-tea method, establishing the GAD enzyme and its pH trigger mechanism [1].

1995–2017 · Mechanisms deepen Animal trials of GABA-rich green tea [9]; the dual pathways of the GABA shunt and polyamine degradation are worked out, along with gene- and protein-level regulation of GAD [2][3].

1994 / 2004 · Taiwan localizes TRES studies the technique in Japan, re-engineers it around oolong, promotes it domestically, and creates GABA oolong tea [12].

2006 · Taking stock of the chemistry A primary Taiwanese study compares the composition of GABA tea and green tea [14].

2018–2024 · Process and flavor go modern Anaerobic–aerobic sequential pathways [4]; Taiwanese consumer sensory profiling [11]; market quality surveys [15]; multi-omics aroma mechanisms [13].

The most interesting thing about this timeline: the early studies laid foundations in mechanism and process, while the more recent the work, the more it shifts toward making the tea taste better and keeping its quality honest — the natural arc of a food product moving from the lab bench into everyday cups.

Nothing shows the power of the process like one dataset from that original 1987 paper. Using isotope-labeled nitrogen (¹⁵N), the researchers tracked GABA accumulating steadily over time once oxygen was cut off, while the aerobic control barely moved:

Over the same six hours, the aerobic group's GABA crept from 0.86 up to just 2.57, while the anaerobic group surged to 18.86 (all in μmol/g) [1]. That is the most direct first-hand evidence behind the rule "less oxygen, more GABA." As for the "10- to 20-fold" increase that modern reviews like to cite: it actually comes from later studies (such as the roughly 20-fold figure reported in 2017) [2][6], not from the 1987 original — under the original paper's conditions of unfed, natural fresh leaves incubated for just six hours, the increase was about 8.9-fold [1]. The attribution gets mixed up often enough that it is worth setting straight in passing.

GABA Tea on the Taiwanese Market

In Taiwan, Gabaron tea has become a rather mature category. One survey spanning 2016–2021 collected 220 commercial GABA teas, sorted them into five categories, and tested every sample for content. The results were impressive: about 87.7% met the commercial labeling threshold, with only about 10% (22 samples) falling short — and among GABA oolongs and GABA black teas alone, the pass rate topped 90% [15].

Each category also has its own characteristic content range — GABA black tea runs highest, while GABA oolong is the most common and the most consistent, with most samples sitting comfortably above the labeling threshold:

The Trade-off Between Flavor and Composition

One thing deserves an honest airing. If oxygen starvation forces the leaf to pour its resources into GABA, do other components shift along the way? They do — and that turns out to be an important lesson in understanding this tea.

A 2006 Taiwanese study compared GABA tea with green tea and found the GABA tea lower in total catechins, EGCG, and related compounds, with no significant difference in caffeine [14]. On the catechin decline (catechins being the main source of astringency in the cup — think of them as the leaf's natural antioxidants), multiple studies agree [6][14].

The other oft-repeated claim — that theanine drops — actually has no consensus behind it. The 2006 Taiwanese study measured no significant difference in theanine between GABA tea and green tea [14], while some modern reviews report that theanine falls markedly under long commercial processing [6]. In the short-duration 1987 experiment, theanine dipped only about 12% over 12 hours — hardly a collapse [1]. The safer summary is this: the evidence for the catechin decline is fairly consistent, while theanine varies with processing length and tea type, and the studies disagree — the longer the leaves are sealed, the more the composition shifts.

For the full story on theanine itself — the leaf's natural "calm" amino acid — see our piece on [high-mountain tea and theanine](/articles?slug=high-mountain-theanine). One aside worth noting: the "anaerobic" step in Gabaron tea and the "oxidative fermentation" of ordinary tea are two different things — the former is enzymatic conversion under oxygen deprivation, the latter is polyphenol oxidation, and the pathways have nothing in common. For that side of the story, see [how tea fermentation works](/articles?slug=teafermentaition).

One line to remember about process and composition: Gabaron tea is not "a more nutritious tea" — it is a tea whose composition has been reallocated. It trades higher GABA and lower catechins for a distinctive fresh, gently tart character. If you love it, what you love is exactly that difference.

The Health Question, Honestly

By this point someone always wants to ask: with GABA this high, will drinking it relax me, help me sleep, lower my blood pressure?

Here honesty and restraint are both required. GABA is a real compound, and there are indeed some early human studies exploring it — but whether drinking the tea actually does anything for the body remains an open question in the scientific community. A systematic review pooling 14 studies concluded that oral GABA has only limited evidence for effects on stress and very limited evidence for sleep, with many of the underlying studies small and lacking controls [7]. Beyond that, a cup brewed from 3 g of leaves works out to only about 4.5–5.6 mg of GABA (estimated from label values, not directly measured) — an order of magnitude below the hundred-milligram doses typical of supplement research [8].

Where we stand: in keeping with food-safety regulations, we make no therapeutic claims for Gabaron tea — no promises of better sleep, lower blood pressure, or relaxation. The discussion above is a neutral account of the state of the research and the strength of the evidence. Treat it as a fresh-tasting tea with a great scientific backstory, and you have exactly the right attitude.

What This Cup Comes Down To

  1. It is a craft tea made by smothering the leaf. In 1987, researchers in Japan sealed fresh leaves under nitrogen until the oxygen ran out, letting the GAD enzyme stockpile GABA; Taiwan's TRES then rebuilt the process around oolong, trading away the sourness and stuffiness for a floral GABA oolong with a returning sweetness [1][11][12].
  2. Its value lies in flavor and distinctiveness, not in being "healthier." High GABA comes at the price of lower catechins and a fresh, gently tart profile — a tea whose composition has been reallocated into something all its own [14].
  3. The health effects are unsettled; enjoy it simply as a good tea. The research is still early and the evidence limited, and we make no therapeutic claims [7]. If it relaxes you, that may owe more to the ritual of sitting down and brewing it slowly.

References

  1. Tsushida, T. & Murai, T. (1987). Conversion of Glutamic Acid to γ-Aminobutyric Acid in Tea Leaves under Anaerobic Conditions. Agricultural and Biological Chemistry, 51(11), 2865–2871. https://doi.org/10.1080/00021369.1987.10868498
  2. Mei, X. et al. (2017). γ-Aminobutyric Acid (GABA) Accumulation in Tea through GABA Shunt and Polyamine Degradation Pathways under Anoxia. Journal of Agricultural and Food Chemistry, 65(31). https://doi.org/10.1021/acs.jafc.7b00304
  3. Mei, X. et al. (2016). Dual mechanisms regulating glutamate decarboxylases and accumulation of gamma-aminobutyric acid in tea (Camellia sinensis) leaves exposed to multiple stresses. Scientific Reports, 6, 23685. https://doi.org/10.1038/srep23685
  4. Accumulating pathways of γ-aminobutyric acid during anaerobic and aerobic sequential incubations in fresh tea leaves. (2018). Food Chemistry. https://doi.org/10.1016/j.foodchem.2017.08.056
  5. Effect of Anaerobic Treatment on Volatile Flavor Characteristics in GABA White Tea. (2025). Foods, 14(7), 1153. https://doi.org/10.3390/foods14071153
  6. GABA-enriched teas as neuro-nutraceuticals（綜述）. (2020). Neurochemistry International. https://www.sciencedirect.com/science/article/abs/pii/S0197018620302862
  7. Hepsomali, P. et al. (2020). Effects of Oral Gamma-Aminobutyric Acid (GABA) Administration on Stress and Sleep in Humans: A Systematic Review. Frontiers in Neuroscience, 14, 923. https://doi.org/10.3389/fnins.2020.00923
  8. Versatile Effects of GABA Oolong Tea on Diastolic Blood Pressure, Alpha Brain Waves, and Quality of Life. (2023). Foods, 12(22), 4101（製程事實：實測 187 mg/100g、常見標稱門檻 ≥150 mg/100g）. https://doi.org/10.3390/foods12224101
  9. Effect of green tea rich in γ-aminobutyric acid on blood pressure of Dahl salt-sensitive rats（動物研究，證據等級對照）. (1995). American Journal of Hypertension, 8(1), 74–79. https://pubmed.ncbi.nlm.nih.gov/7734101/
  10. Oketch-Rabah, H. A. et al. (2021). United States Pharmacopeia (USP) Safety Review of Gamma-Aminobutyric Acid (GABA). PMC8399837. https://pmc.ncbi.nlm.nih.gov/articles/PMC8399837/
  11. Understanding Young Taiwanese Consumers' Acceptance, Sensory Profile, and Drivers of Liking for GABA Oolong Tea Beverages with Cold Infusions（一手感官研究＋「兩好氧三厭氧」製程序列）. (2022). Foods, 11(19), 2989. https://doi.org/10.3390/foods11192989
  12. 農業部知識入口網：無氧發酵保健茶—佳葉龍茶異軍突起（官方農業推廣資料，記載 1994 赴日、2004 推廣、烏龍改良脈絡；年代／數字宜與學術來源交叉）. https://kmweb.moa.gov.tw/knowledge_view.php?id=54125
  13. Combined multi-omics approach to analyze the flavor characteristics and formation mechanism of gabaron green tea（一手，多組學香氣機制）. (2024). Food Chemistry. https://doi.org/10.1016/j.foodchem.2024.138645
  14. Comparison of bioactive components in GABA tea and green tea produced in Taiwan（一手，台灣 56 件茶樣比較）. (2006). Food Chemistry. https://doi.org/10.1016/j.foodchem.2005.03.036
  15. Investigation on the Quality of Commercially Available GABA Tea in Taiwan（一手，220 件市售品質調查）. (2023). Standards, 3(3), 22. https://doi.org/10.3390/standards3030022

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