White tea is the black sheep of the tea family. Like many black sheep, it’s been bent to fit a narrative that doesn’t quite do it justice. This narrative I call the fermentation narrative, and it goes, green tea (non-fermented), oolong tea (semi-fermented), and black tea (fully-fermented). This narrative is, for the most part, true (except for the semantics behind the term “fermented”). As for white tea, it would be great if we could tack it on with the other teas in that narrative. But where? Well, white is the opposite of black… and if black is the most fermented, then white tea should be least fermented, right? Like yin and yang, my point here is that some things just sound right. They seem sensible at first glance, and so they stick. Stephen Colbert calls this concept “truthiness,” and white tea is a topic enshrouded by a great deal of truthiness.
From Confusion to Clari-tea
A common white tea misconception is assuming that “white” implies little or no fermentation. It’s a legitimate point of confusion because if you start with black tea being fully fermented and work backward from there, it makes sense that white tea would be least fermented. It also doesn’t help that there has been confusing scientific data produced on the topic in the past. Whatever the reason, there is no point in settling for truthiness when we can have the truth. White tea can fit nicely into our fermentation narrative, just not at the position of non-fermented tea. It’s a semi-fermented tea, like oolong, but in fact more fermented than the average oolong tea.
The “white” in white tea is a misnomer, in that it is not the lightest in color or flavor, or fermentation, or caffeine content. We have some truthiness to unfold, but by GOLLY is it worth it. White tea is an underappreciated tea type with exceptional characteristics; sweet, savory, versatile, long-lasting, and health benefits unique to only itself. Let’s dive into what makes white tea unique.
How White Tea is Processed
Varying degrees of fermentation result from deliberate, often intricate processing steps that create teas which are non-fermented, semi-fermented, or fully-fermented. Fortunately, white tea requires very little processing, making a conversation about white tea processing quick and easy. White tea processing has two steps after plucking;
1. wither the leaves 2. dry the leaves. Most important of those two, and the key to understanding white tea, is step 1, Withering.
Withering is so easy a caveman could do it. Even a cave-boy or a small cave-child could excel in tea leaf withering. All one has to do is take freshly plucked leaves, spread them out on a tarp, or in a trough, or a cave-dwelling, and wait patiently for 24 to 36 hours (on average) for air to dry out the leaves (duration of withering time varies depending on air temperature and humidity conditions). So, that’s it! Just let the leaves sit out for a day.
But, as simple as it sounds, withering significantly changes the biochemical properties of tea leaves, and ultimately determines the unique characteristics of white tea color, aroma, flavor, antioxidant capacity, and more.
Fortunately for us, tea scientists around the world, including friends of The Tea Spot at the Tea Research Institute in Hangzhou, China have conducted quality studies tracking precisely what happens to tea leaves during white tea withering.
What is Fermentation?
Before diving into the science, we need to take a second look at the fermentation narrative and translate that into something more science-based. Fermentation, in the context of this discussion, means polyphenol oxidation and the transformation of green tea polyphenols (catechins) into black tea polyphenols (theaflavins).
So, in our fermentation narrative, non-fermented green tea means lots of catechins and no theaflavins, semi-fermented (oolong or white) means fewer catechins and some theaflavins, and fully fermented black tea means nearly no catechins and lots of theaflavins. Fermentation, thus, is a shift from catechins to theaflavins.
Sometimes, scientists get lazy, and they compare degrees of fermentation between two teas of entirely different backgrounds (one from Japan and one from Kenya), where catechin contents already vary highly due to different cultivar, growing conditions, transport methods, etc. This is where studies from the past have gotten confusing.
For this reason, the only way to truly measure how tea processing (and only tea processing) affects tea leaves is to use fresh leaves from the same batch of freshly plucked leaves, split them up evenly, and then process each identical group into different tea types (green, black, oolong, etc). Then, you can compare and contrast which tea type is relatively fermented, or rich in caffeine, L-theanine, or whatever it is you would like to test. That is exactly what our friends at the Tea Research Institute in Hangzhou did in order to test the effects of white tea withering on the biochemical profile (including degree of fermentation) of white tea [1].
White Tea Research Explained
In this study, a single batch of fresh leaves was split evenly into three groups, and processed into green, black, or white tea. Examine figure 1, and notice the color of the leaves and the liquor. Nothing all too white about the white tea, except for the silver hairs on the buds (how white tea originally got its name). The liquor is far less light in color than that of green tea. And under the hood (meaning the microscope)…
Figure 1
“Catechins, including EGCG […] were at lower levels in white tea and had the lowest levels in black tea when compared with those in green tea. This result is consistent with the fermentation degree in that black, white, and green tea is fully fermented, slightly fermented, and non-fermented, respectively. However, these results are different from Santana-Rios’s findings [2], who reported that white tea had higher contents of [catechins] compared with green tea. This contrast might be due to the inclusion of different varieties of white tea and green tea in Santana-Rios’s work, whereas the same batch of tea leaves was included in this study.”
We see here that holding all other variables constant (by using the same batch of leaves to start with), white tea processing meets at least one criterion of fermentation, being that catechin content drops. Catechins decrease, but what black tea theaflavins?
“Theaflavins […] were at significantly high concentrations in white tea because of the slight fermentation, but levels were much lower than those in black tea.”
So far, the Hangzhou study has shown lower green tea catechins, and more black tea theaflavins in white tea. Let’s look at another relevant factor… the case of methylated catechins.
Super-Catechins to the Rescue!
Methylated catechins are like “super-catechins,” capable of stronger anti-allergic [3,4] anti-hypertensive [5], anti-oxidant [6], anti-obesity [7], and probiotic [8] effects than normal green tea catechins, such as EGCG. Methylated catechins are particularly present in oolong teas, but not in black tea, because these catechin derivatives are consumed in the process of heavy fermentation required for black tea processing [9,12].
Several types of methylated catechins have only been able to be isolated from oolong teas [10], presumably because methylation results from bioactive processes involved in semi-fermentation. Methylated catechins increase with some fermentation, but then decrease with too much fermentation, taking on a bell curve shape in relation to increasing fermentation. As for the methylated “super-catechin” content in the study, we are reviewing…
“methylated catechins […] exhibited the highest contents in white tea compared with green tea and black tea. Because methylated catechins are consumed during [heavy] fermentation, […] it is assumed that the methylation of catechins may occur during the prolonged withering process of white tea.”
Although total catechin content drops during white tea production, methylated catechin content increases. This flux leads to lower total antioxidant power for white tea (as more total catechins means more antioxidant power [12,13,14]), but this fermentation-driven change also leads to the creation of methylated “super-catechins,” capable out-performing normal catechins in the health benefits mentioned above. Different tea types offer their own unique health benefits, which is why it’s good to diversify your tea stash.
To quickly review what these results mean for the fermentation status of white tea —
Withering leads to green tea catechins down, black tea theaflavins up, oolong methylated catechins up — These are signs highly indicative of fermentation. Which makes sense, looking at white tea’s darker liquor color, sweeter, less astringent taste, and floral/fruity aromas, as opposed to grassy/green notes in a truly non-fermented tea.
The Sweet Effects of Amino Acids
I can’t end a conversation on white tea without mentioning my favorite aspect of white tea processing, which is… the increased content of sweet and savory amino acids. Amino acids are so essential to tea flavor, I cannot stress it enough. These are the MVP’s of the tea leaf. They offset the bitterness/astringency of polyphenols, give tea it’s brothy, savory/sweet, umami profile. And they provide anti-stress/anti-anxiety effects in the brain [19], which work synergistically with caffeine to provide us with that one-of-kind relaxed focus only found in a cup of tea [15].
A number of studies have shown that white tea contains more amino acids than green or black teas [16,17]. The reason? Amino acids form proteins in tea leaves, and during prolonged withering, these proteins break back down into their original amino acid building blocks, causing total amino acid content to rise [18]. Below is a figure from the Hangzhou study measuring the contents of 12 different amino acids over the span of a 36-hour white tea withering period [1].
Figure 2
As you can see, amino acid content increases, leading to a more savory/sweet flavor and greater cognitive/mood effects in the brain.
What we’ve shown so far is that white tea is a partially fermented tea, containing more antioxidant capacity than a black tea, more theaflavins than a green tea, and more methylated “super-catechins” than either of the two. On top of that, a long withering period breaks down proteins into tasty amino acids that improve both flavor and mood. This is not an exhaustive explanation of what makes white tea great, but it can introduce the basic kinetics behind white tea chemistry (fueled by the withering process) and can serve as a guide for where to place this tea within our fermentation narrative.
As for types of white tea, the main two are Bai Mudan (or White Peony) and Silver Needle (or Bai Hao Yinzhen). These two tea types vary in that White Peony consists of one bud and two leaves, while Silver Needle consists entirely of buds. The bud of the tea plant is precious because it contains relatively more amino acids, which gives it a sweeter and more savory taste than leaves of the tea plant. The first and second leaves, however, contain more total catechins than buds do. Extra catechins provide White Peony with a more robust body than Silver Needle’s lighter, sweeter infusion.
Both teas often are made using similar tea tree cultivars (Da Bai cultivars) from Fujian, China. While some people prefer White Peony due to its more stimulating taste, Silver Needle tends to command a higher price due to the more labor-intensive plucking process essential for producing tea made entirely from buds. For this reason, some call Silver Needles the “champagne of tea” (but feel free to use a less pretentious nickname if you’d like). Aside from differences in the amino acid/catechin ratio, which affects taste and mouthfeel, White Peony and Silver Needle white teas are more similar than they are different. Both teas are semi-fermented through a long withering process, then dried.
My tea biochemistry professor, Huang Yahui, a leading world expert in tea processing chemistry, told me recently, “Among green, oolong, and black teas, the closest relative to white tea would have to be black tea.” The reason being that white tea contains theaflavins, a black tea polyphenol that even oolong tea doesn’t produce. This is because a 36-hour white tea wither is kind of a big deal. This processing time is significant, more than doubling standard oolong tea processing, which averages around 12-16 total hours of processing time.
White tea invites a sense of truthiness, suggesting light fermentation, untouched leaves, and unadulterated metabolites. However, there’s nothing insignificant about a 36-hour withering period. Catechins change, theaflavins are formed, and amino acids increase in number. While there is much more to this topic, for now, one thing can be said for certain; the only thing black and white about white tea is that it deserves a spot in your top-tea lineup.
As always, reach out with questions or comments. Follow @theteaspot on Instagram and hashtag us with all your tea-related posts. Thanks for reading, and stay tuned for more awesome tea-based content!
Resources
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