The Science Behind a Bold but Balanced Tea Infusion (Part 2)

Polyphenols, being larger-weight molecules, require more of kick in the rump than amino acids do in order to extract them out of the leaf, and into the cup. The extra umph can be hotter water, longer infusion time, or more leaf agitation (stirring, prodding, poking, etc.).

Ducksh*t Oolong getting a kick in the rump

Since discovering the health benefits of tea polyphenols (TP), scientists have experimented with nearly every method imaginable to find the optimal conditions for their extraction. In the literature, it’s common to come across TP extraction studies with methodologies such as: ultrasound assisted extraction, microwave assisted extraction, high pressure processing, supercritical fluid extraction, subcritical water extraction [24]… (Sir, would you like your Matcha Latte tall or venti? And please choose between ultrasound assisted microwave extraction, or supercritical fluid extraction)

The aim of those studies is to extract pure tea polyphenols for use in pills or supplements [25], but what we care about is the water-only extraction research. The data is variable, but on average, peak polyphenol concentrations with water extraction was achieved using a 30-minute extraction at 80°C/175°F (after 30 minutes TPs start reacting with oxygen and degrading) [26, 27].

Let’s linger on that last sentence for a moment. Have you ever (presumably by accident) brewed your green tea at 80°C/175°F for 30 minutes? That is what peak tea polyphenol extraction tastes like.

The point is that “optimal polyphenol extraction” is not optimal tea infusion, since tea leaves possess far more bitter polyphenols than any (even moderately masochistic) person could find palatable.

To illustrate the drawn-out process of TP extraction, below is a figure from one of the above-mentioned TP extraction studies (a normal water-only one). The study measures total polyphenol content (TPC) of 3 teas (green, oolong, and black) for 3 subsequent 5-minute infusions at 90°C/194°F for each tea [28]. 3 teas, 3 infusions per tea.

The important trend in the data is this relatively insignificant difference in polyphenol content (TPC) between the first and second infusions for all three teas. What happened in all three teas was a bold, polyphenol-rich first infusion (of five minutes)… and then right afterwards, another nearly equally bold, polyphenol-rich second infusion. By the third infusion, things drop off more, but TPC still remains pretty high.

Think of how mismatched this is with tea amino acid (AA) extraction. After 90 seconds, most AAs have been extracted out of the leaves. Meanwhile, 15 minutes later, bitter tea polyphenols continue to pour out of the… poor, bitter…God forsaken leaves… of pain (I was born to write tragedies not science blogs).

Green teas can be bitter if brewed too long, but Ripe Puer Tea (above) stays smooth no matter what (explained below)

You can imagine, then, that according to your personal preferences, there exists optimal parameters of extraction for each tea – a point at which enough amino acids and polyphenols have come out to co-create a flavorful brew, yet the AA/TP ratio has not diminished into bitter oblivion. A well-balanced and flavorful brew is the goal.

The reason I say optimal parameters ‘for each tea’ is that there are so many factors affecting the ultimate AA/TP concentrations in your cup, and even factors affecting what you personally taste and enjoy, that each new tea demands its own recalibration to find your optimal extraction parameters for that tea.

Let’s go through some things that affect what the ideal extraction parameters might be.

Tea type (green, black, oolong, white or dark) is important. Despite all deriving from the same leaf, these tea categories undergo starkly different processing that alters the state of the tea polyphenols considerably. Without getting into too much detail, the most bitter and astringent tea polyphenols are called complex catechins, which include ECG and EGCG. Their concentrations decrease with tea type in this order: green tea > oolong tea > white tea > dark tea > black tea [29]. This means that, holding all else equal, a 2min 30sec 80°C/175°F infusion of green tea might taste too astringent, while the same extraction parameters for a black tea might be good (or possibly not strong enough).

Another factor is the physical state of the tea leaves. For example, green and black teas typically get rolled during their production, which serves to break down tea leaf cell walls and ease extraction later during infusion. White tea on the other hand, does not get rolled, meaning more intact plant cell walls, and more time/higher heat necessary to extract a flavorful brew.

Hand-rolling Yunnan green tea

A recent study found that the most highly ranked white tea infusion among a trained panel of judges used water temperature of 98°C/208.4°F (aka boiling hot), compared to 90, 80, 70, and 60°C water temps [30]. Why? White tea is neither rolled nor is it abundant in bitter complex catechins, so the polyphenols themselves are neither overly bitter nor easily extractable.

In previous blogs I have castigated the widespread myth that White Tea should be brewed at low water temperatures… humph! (castigations found here).

Now to my final point… AA/TP is a ratio, not a sum. This means that AA-rich teas are able to possess high concentrations of bitter polyphenols and still not taste bitter, thanks to the masking effect of savory AAs. This is the holy grail of tea, and why Spring Flush teas are so sought after. It’s not that bitter polyphenols are bad – in fact they’re necessary – it’s that you want them as part of a balanced ratio of compounds that synergize to create bold, full-bodied flavor.

Rich abundance + good balance = fantastic tea

A bold yet well-balanced infusion of Yunnan Moonlight White Tea

Now for a quick rapid-fire before you go:

  • Type of water significantly effects polyphenol extraction and tea flavor quality [31].
  • Tea cultivars vary significantly in both esterified (bitter) TP and total AA [32, 33].
  • Season of cultivation plays a significant role in TP, AA and caffeine concentrations [34].
  • Bitterness tolerance depends on your receptor sensitivity and personality [35].
  • Likewise, bitterness affects mood and emotions [36].
  • Both tea farm latitude and altitude play significant roles in TP and AA accumulation [37].
  • My mom thinks I need to find a girlfriend.

Great points all around, and certainly lots of valid science to consider there.

I will close things up with this: No steeping instructions are objectively correct. But, if you’re utterly befuddled… start with 80°C/175°F for 5 minutes. If that is too bitter, go down (in terms of time and/or temperature) on the next one, if it’s not strong enough, go up. Tea infusion is a skill to be practiced and mastered over time, not a straightforward recipe. In the leaf, high AA and TP concentrations + good balance = fantastic tea. Infuse your White Tea long and hot.

That’s it! Feel free to comment here, or DM me on Instagram @WuMountainTea

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