Some More Unsung Heroes
I, in my love of warmth, have held out for as long as I can. But, I can do so no longer: it is Fall - the time of year when I begin to question why I live in Minnesota. But hey, at least it makes our shipping times to both coasts roughly the same!
In any case, there is, of course ,beauty in fall. The leaves change from bright green to orange, yellow, and red. This is one reason why a lot of people really love this season. You may even know why this process occurs, but I'll fill you in, just in case. As light diminishes, the chlorophyll that gave the leaves their green color dies off, revealing the carotenoids that were there all along. Carotenoids play a supporting role in photosynthesis, and reflect back those warm-colored wavelengths of light we love. The carotenoids are always present, but normally obfuscated by the chlorophyll.
Well, tea plants are evergreen, so we never get to see pretty tea fields of orange and yellow and red. Nonetheless, they, too, contain carotenoids, and these play a significant role in shade-grown teas in particular. Let's get into it!
Carotenoids in Shaded Tea
Carotenoids help a plant to absorb a wider spectrum of light wavelengths. When a tea plant is shaded, it pulls out all of the stops to photosynthesize more effectively. This leads to the famous and dramatic increase in chlorophyll that is found in shaded teas - the reason matcha is so green and perfectly-colored to go viral on social media.
However, in the background, shading causes carotenoid concentrations to increase as well, with shaded teas found to have substantially higher levels of these molecules.
Now, to get a little more specific, carotenoids refer to a whole class of pigmented compounds found throughout nature, and there are many varieties of them. The most famous is Beta-Carotene, which gives carrots their orange color. The carotenoids most abundant in tea include the following:
Lutein, Beta-Carotene, Alpha-Carotene, Violaxanthin, and 9-cis-neoxanthin.
If we can't see them, why care about them?
The role of carotenoids in tea is interesting because, unlike with chlorophyll, the increase in carotenoids alters the flavor and aroma of the finished tea substantially. What's more, whereas increases in chlorophyll in shaded teas are predictable, the increases in carotenoids are more random. That is to say, some cultivars will produce more Beta-Carotene, others will produce more Lutein, and so on. I tried to find information on which cultivars produce which carotenoids, but that research seems to be lacking so far. Fair enough - there are so many cultivars and the concentrations of these molecules depend on more than just the cultivar type, but on growing conditions in general. In any case, it is enough to know that the ratios of different carotenoids in the tea vary quite widely.
Now, carotenoids themselves often don't taste like much. However, they break down quite easily, especially during tea processing - and it is this that contributes unique flavors and aromas to a tea. This is what a lot of tea processing is about. The heating, the drying, the shaping, the withering - it is all to create a window for these molecules to break down and form something new. In the context of tencha, the steps that would allow for the breakdown of carotenoids are the initial harvest (and the time the tea leaves sit before being processed), the steaming of the leaves, and the drying of the leaves. Then, after milling the matcha, the rate of breakdown as a result of aging increases rapidly.
Here's where it gets fun (really geeky).
I may not have been able to find research on which cultivars contain which carotenoids, but, I have been able to learn which carotenoids turn into which aromatic molecules.
Beta-Carotene will turn into Beta-Ionone and Beta-Damascenone, associated with notes of violet, rose, and apple.
Lutein will turn into Theaspirone and its derivatives, which gives a sweet, green wood, almost camphor-like fruity note (I have a vial of this for my cologne-making side-hustle, it's good-smelling stuff. Yes, I'm a weird dude with too many hobbies).
Other minor carotenoids often break down into the same molecules as above, or even more obscure molecules associated with tropical fruits. But, another interesting one is Zeaxanthin, which breaks down into Safranal, one of the main odor components of Saffron!
Over time, even after the leaf is dried and milled into matcha, the process of breakdown continues. Molecules combine and increase in concentration. Small amounts of Beta-Ionone and Alpha-Ionone are associated with pleasant floral scents, but when they accumulate past a certain threshold, the brain processes them as a "stale odor." That is to say, you want to catch your tea at just the right moment so that the concentrations of these different molecules come across as pleasant - and that's where freshness comes in. Soon as we're talking about aromatic molecules, we're talking about the most volatile aspects of tea. When your matcha isn't freshly-milled, it's basically the Wild West in terms of how these molecules interact, and it is often for the worse. If you want to read more about that, check out this old blog post of mine.
I would love to also be able to say that all of our naturally-farmed tencha is inherently higher in carotenoids than synthetically farmed tea, with a resultant greater diversity of the aromas they produce, but the evidence on that front seems to be contradictory and all over the place. Some studies show organic farming produces more carotenoids, some show it produces less. And then, again, who knows how this changes depending on the cultivar that is being studied? Really, there seems to be a common thread when it comes to carotenoids in tea: they are unpredictable, but they sure do matter.
Thanks for reading, and happy sipping,
Simon