With exams finally over, I have a life again and can hopefully post several times a week from here on out. Anyway, here's a zhuancha that I received back in December as the result of several recommendations. After some discussion concerning its loss of flavor on RFDT, I felt it necessary to try it again for myself. To be completely honest, I hardly remember the first time... my mind was probably elsewhere. Hence this was a nice time to catch up on what I had originally neglected.But first, some background information:
This Zhuancha is of the somewhat rare purple-leaf varietal (for lack of a better word) and consists of medium to large grade leaves, some of them broken/chopped (which may have been the result of my prying into the tightly compressed brick). Some photos of the leaves:
(WARNING: CHEMISTRY CONTENT!)
The purple tinge in the leaves is the result of a class of compounds known as anthocyanidins. Anthocyanidins are polyphenols which are important antioxidants found in tea and many other foods (We all hear antioxidant thrown around everywhere nowadays, but if anyone is interested in what it actually means/how they work, let me know and I'll include it in another post). While anthocyanidins are only one class within the huge designation of polyphenol, somewhere around 300 of them have been discovered/cataloged to the best of my knowledge. The variances between these 300 are due to differences in the 'R' groups designated in the structure below. For a compound to be considered a polyphenol, two phenyl groups (a 6-carbon ring with 3 double bonds - i.e. the top right ring on the picture) must each have at least one hydroxyl (-OH) group bonded to it and but be joined to one another. On anthocyanidins, the majority of 'R' groups turn out to be hydroxyls, with variances of only one or two other 'R's between them, but I digress.
The reason anthocyanidins are produced in plants has to do with the amount of sunlight it receives. Consi
der it analogous to you skin becoming tan - the more sunlight the leaves receive, the more anthocyanidins are produced to shield it from the intense rays. While cholophyll absorb every wavelength of light except green (hence how we see it as green - it is the only color reflected off it) anthocyanidins absorb only blue-green light (and are therefore seen as purple-red) and are produced in young leaves before a sufficient amount of chlorophyll are produced - they're basically a band-aid until the chlorophyll can take over absorbing light. Also, because the compounds are polyphenolic antioxidants, the radicals (unpaired electrons that cause chain reactions forming more unpaired electrons and disrupt cell activity) formed from UV exposure get absorbed and eliminated - a two-fold win for the plant. Again, if there's any interest I can write a short disambiguation about polyphenols, why they're good, and how they work... Or not.Scott at YSLLC explains that this happens in tea plants when the rainy season washes away dust in the air that would otherwise diffuse UV light. To protect themselves, the young tea plants produce more anthocyanidins (to the best of my knowledge the exact anthocyanidins in C. Sinensis have yet to be established) and take on the characteristic purple-red tinge. This tends to happen fore frequently at lower altitudes as the leaves are not accustomed to the high levels of UV radiation that reaches the high-elevation plants. As an aside, I find it interesting that the degree of purple and red color observed has to do with the pH of the soil that the plant is growing in - acidic conditions tend toward red and basic toward purple-blue. Apparently, only 1-2% of all tea plants have these purple leaves, which makes sense because the plant will cease production of anthocyanidins once enough chlorophyll have been produced to protect the plant from the UV radiation.
Now, on to the tea :-)
If you've made it this far, you must really want to know what I think about this tea. Well, I think I liked it. The tea started off very smooth for such a young tea. Just as Scott at YSLLC described, there was almost no bitterness present - it was pretty enjoyable. The dry leaves had a slight dirt-like aroma that wasn't all that pleasant, but when infused both the liquor and leaves lacked the off smell. The wet leaves actually gave off a very strong aroma of menthol which took me off guard. The liquor had a slight menthol effect in the first several infusions, but dropped off suddenly around the 4th - as did the liquor in general. I used my standard infusion times for the tasting, but the leaves clearly needed longer steeping times beginning with the 4th. The middle steepings were sweet, watery, and pretty boring. Then, somehow, the tea decided to explode in the cup on the 8th infusion - the liquor was thick, juicy, and very thirst quenching. This lasted only 2 infusions until I gave up at 10 when it returned to its watery sweetness of 4-7. Here are pictures of infusions 2, 6, and 10, respectively - note that 8 was right in line for the progression of color; nothing abnormal:
Some tasting notes:(Parameters: 5g dry leaf in 100mL gaiwan; filtered tap water; 15s rinse, 20s, 15s, 15s, 20s, 30s, 60s, 105s, 180s, 270s, 360s)
(1): No bitterness present at all. Spicy/tangy sweetness noticeable. Very smooth, slight menthol present. Coats the throat completely. Leaves give off strong menthol aroma.
(2): Slight bitterness present but sweetness still noticeable. A hint of smokiness present, but overall the liquor is still very smooth. A very slight odd, dirt-like hint in background - not enough to be unpleasant.
(3): Very strong menthol aroma from leaves. Smooth sweetness and light astringency mixing very well. Grain notes present.
(4): Light sweetness present. Watery - leaves need longer steeping. Wet and smooth down the throat.
(5): Still smooth, menthol noticed in throat and mouth. Light sugary sweetness detected alongside light spicy/smokiness. Slightly too weak.
(6): Light menthol-sweetness still present. Very light but still manages to coat the throat.
(7): Smoky-menthol still emanating from leaves. Wet and juicy but watery at the same time. Liquor still manages to hold its light sweetness despite the wateriness.
(8): Thick, sweet, and juicy - very pleasant and thirst quenching. Sweetness lingers strongly on the back of the tongue. Menthol now strongly present also. Aftertaste reminiscent of a plum. Wonderful.
(9): Sweetness/menthol strongly present - similar to camphor notes but not the same. Noticeable fruit (plum?) aftertaste. Very smooth despite the previous wateriness.
(10): Mild sweetness dominating. Menthol still present, but not nearly as noticeable. Watery.
(11+ would not yield too much - leaves are spent)
I'm not really sure how I feel about this tea. On the one hand, it was very weak and didn't have much to offer in the middle infusions after a pleasant but not outstanding beginning. On the other, the finish was spectacular - the juiciness of the liquor sums it up best - and left me forgetting about its previous mediocrity. Overall, I think that this is a good tea to drink now with an average (~5g) of leaf and long infusion times. Although I don't expect much in terms of aging, I'm content with the 2 bricks I purchased. 5.5/10
tb.
9 comments:
Hello,
I really enjoy your chemist's perspective on this tea here. I would be fascinated to hear more about polyphenols/flavonoids/antioxidants and what the difference between them is. I also have a specific concern that you may be able to answer. Have you heard that putting milk in your tea (maybe not a concern for a connoisseur of oolongs) purportedly eliminates its healthful benefits?
Here is the most complete article I found on the subject: ScienceDaily article
I wish I knew more about how the body breaks stuff down, because if they think that milk caseins form bonds with the antioxidants in tea, maybe those newly formed compounds just sit around in the stomach for a while until they are broken down by digestion and then absorbed as they normally would be.
Another reason these findings aren't totally convincing is their insistence on the word 'catechins.'--
"Their study showed that the culprit in milk is a group of proteins called caseins, which they found interacted with the tea to decrease the concentration of catechins in the beverage."
Other articles say that they only suspected the casein-catechin interaction but didn't know for sure, even though they also refer to the same study. In any case, my contention is that while green tea has a large concentration of the catechin type polyphenols, black tea only has about 1/4 the amount. Catechins are converted to theaflavins during the tea oxidation/fermentation process, an entirely different class of flavonoids which are practically non-existent in green tea but abundant in black. Theaflavins are responsible for the antioxidant activity that give black tea its benefits, and would presumably cause the arterial dilation. In any case, milk does appear to bag this benefit in particular, but either the article or the scientists are mistaken as to the reason why.
And is the effect simply delayed rather than removed, until the body breaks the casein compound down? I mean, that is what digestion is for??
Let me know what you think...
Hi Alex-
Somehow your comment was able to fly under my radar for a few days... Sorry for that!
First, as a disclaimer, I am by no means an authority on the subject of tea or even on biochemistry (at least not yet :) ). My insights are only based on what I've read/studied which is most certainly a continuing project. Talk to me in 8 years when I've completed my dissertation and perhaps I'll have a bit more confidence.
Anyway, regarding milk and polyphenols - there was a wonderful article on the biochemistry of tea posted on ChaDao some time ago where a gentleman by the name of Sanwar M. Changoiwala detailed the processes involved in the manufacture of darjeeling black tea (which I suppose should be considered oolong teas anyway!). In it, he explains much of what you just stated regarding catechins and the like - in the black tea oxidation process they are broken down into theaflavins and thearubigens. More theaflavins give the tea a golden-brown color while more thearubigens impart a red-brown color. At any rate, theaflavins do indeed form a complex with dairy proteins - this can be seen as the change of color from red-brown to gold-brown when milk/cream is added. This is because thearubigens polymerize in solution rather than form a protein complex like theaflavins, hence the color chance. With that said, the theaflavins then enter the stomach as a protein/flavanoid complex (and I gather that this is where your question really is). To the best of my knowledge, the protein/flavanoid complex would be stable enough to avoid being broken back down into its individual protein and theaflavin constituents. I don't know for sure, but it's my informed guess that the entire complex would then be broken down - the protein as it normally would, but I could see the theaflavin also being torn apart as it tries to untangle from the conformational mess that the complex probably exists as. At any rate, even if it still retains its theaflavin structure, chances are that it will have lost any beneficial properties that it once possessed simply because it once existed as a complex. Polyphenols are beneficial because their cyclic double bonds absorb free radicals without much fuss, effectively eliminating them. However, once enough are absorbed, the molecule simply can't do any more and becomes (generally speaking) inert. This is more than likely what happens with the protein complex - once the theaflavin has changed its conformation to form the complex, it can't become its original beneficial form again. Once it's done, it's done kind of thing. So I suppose that I agree with the article on that point. However, thats not to say that there are still other flavanoids/polyphenols in black tea that can "survive" milk/cream, but theaflavans in particular do seem to become less beneficial with the addition of dairy.
Some of this is speculation/intuition, so I'll make you a deal. Let me look into this a bit more and I'll make an entry outlining the whole subject of tea and dairy. I can't guarantee much because stereochemistry (3D conformational chemistry) is really freaking complicated, but I can hopefully come up with something other than my own opinion.
My apologies for the long winded response... Great Question!
tb.
As an afterthought for claification - the theaflavin/protein complex would be stable enough to avoid reverting to the protein and the theaflavin as separate compounds but would NOT be stable enough to avoid being broken down by normal digestive processes. Enzymes would go at the protein while the theaflavin disengages, now inert. Hopefully that will clarify the middle section...
tb.
Update:
Looks like casein masks the antioxidant capacity of black tea (particularily theaflavin) and reduces its effectiveness to around 20%, give or take.
Basically, milk will hinder the antioxidant activity of tea by a significant amount, but some of the antioxidant properties will still remain despite the complexes formed. I'll hopefully have real entry completed sometime in the next few days.
tb.
Thank you for the response, tea chemist! I really look forward to your further investigation here. I have become an avid reader of your blog, very fun and informing. I love the merging of east and west mindsets that results from scientifically probing this age old plant/beverage.
By the way, I would love to collaborate and write a more detailed article on this subject. I have started one on my blog, but I don't have enough chemistry knowledge to answer the questions I have. You have definitely helped answer them. They lead to more questions that would need to be answered in a proper article...
"Polyphenols are beneficial because their cyclic double bonds absorb free radicals without much fuss, effectively eliminating them. However, once enough are absorbed, the molecule simply can't do any more and becomes (generally speaking) inert."
I wonder if this means that dairy proteins are some sort of free radical? Or are antioxidants also anti-lots-of-other-things?
"This is because thearubigens polymerize in solution rather than form a protein complex like theaflavins, hence the color chance."
This needs better explanation for a layman such as myself, I am going to try and read up on polymerization and how this differs from the normal bonding that chemistry taught me about.
"Looks like casein masks the antioxidant capacity of black tea (particularily theaflavin) and reduces its effectiveness to around 20%, give or take."
I wonder where you got this as well. And I wonder what the ratio is here, does 1g of casein "gobble up" 1g of theaflavin? What about other tea-born antioxidants?
This is all becoming increasingly more interesting to me... I see that it isn't so simple that AOXs go into the body with the sole purpose of fighting cancer-causing free radicals. They also go after other things. Also, there must be radicals that are necessary to our bodies' functions. Can AOXs be bad if they react with those?
So many questions, I hope to be able to help answer as well! Let me know what you think... :)
A proper post explaining a lot of this dairy stuff is still coming, I promise! I just felt that the diary article would be much easier understood if I took the time to lay out some basics of antioxidants first... But it is in the works! I'll do my stuff here and you can link my post on your blog and ask questions about it there if you want - I'll do my best to answer them there as well.
For some short answers to your questions in the mean time:
1. Dairy proteins aren't free radicals - they're just a big contorted mess of a molecule with all sorts of folds and twists. Some (not all, by far) antioxidants bind to these proteins because either A) the proteins have a receptor site for the AOX for some weird reason, B) sheer chance that enough molecules on each structure bond together effectively fusing the two together, or C) some other reason that I'm leaving out. Basically, I don't really know... I haven't found enough information regarding these specifics (although I'm sure they are out there). Nonetheless, there is some force between the two structures that makes them want to bind together :) Antioxidants aren't exactly anti-lots-of-other-things. I'm sure they react with a host of other molecules, but I wouldn't consider them effective anti-
"X-molecule" agents.
2. Polymerization just means that a bunch of the same molecule bind together to form a long chain. Plastics are the best example - long repeating chains that are very stable (and in some cases, durable!). What I was getting at was that the thearubigens will polymerize with themselves rather that preferentially reacting with proteins as theaflavins would. Because the characteristics of the thearubigens would still be relatively intact, the tea takes on its brownish color rather than the reddish color of theaflavins (which have been "deactivated" by the proteins).
3. I pulled that statistic from here (I think - I didn't read through it again, but it's a great article nonetheless). Google scholar is a great resource for reliable, published information. To be honest - I don't know what the ratio is, although I'd imagine it could vary depending on the conditions of the GI tract at the time. If I recall correctly, other AOX present in green tea (EC, EGC, EGCG) respond in the same manner and degree to dairy proteins. I can't speak of others, however - that would take quite a bit of research.
4. You are most certainly correct about AOX not being on a one way mission for cancer... They can influence a number of things - I'd imagine that they could influence the liver and kidneys considerably (since they would be the ones in charge of processing the molecules). Alas, I'm only a student and the details of how the body processes these molecules are surely over my head. Regarding AOX interfering with normal bodily radical reactions, I suppose it is possible, however unlikely. The body has an amazing ability to streamline reactions along pathways that lab chemists could only dream of reproducing - the enzymes and proteins involved in these reactions mean that they are "sheltered" for lack of a better word and, more importantly, nearly instantaneous. The likelihood of an AOX interfering with these processes is highly unlikely.
I'm really happy that you've taken such interest in this material! It's by no means my specialty, but I hope that I can help you on your way in the slightest bit. Thanks for the great questions... I hope I hit on all of them!
tb.
Wow, thanks for the great responses to my questions!! Judging by your answer to number 4, most radical molecules that are important to the body's functioning are isolated enough by other controls so that they don't go around oxidizing things. This must be why there is a distinct reference to free radicals when talking about AOX's, FR's being a threat since they float around the body freely, ready to attack anything per say. Although I would guess that it would be pretty tough for a FR to come near a DNA strand to be able to "attack" it, especially since the cell badly wants to protect its DNA. If the body has "enzymes and proteins" with the ability to keep the body's own radicals in check, it must have the ability to fight free radicals, especially if they try and come near the king--DNA.
Great response, thank you!! I really look forward to the article. Off I go, I am inspired to blog!!
Actually, radical and free radical refer to the same thing - there's no technical distinction between a radical produced by the body and one created unwillingly.
I honestly don't know how "easy" it is for a radical to disrupt a cell's DNA, but you would be amazed just how often DNA gets damaged and misread. However, the body does have a complex mechanism of "error-reading," for lack of a better term, to fix abnormal DNA segments and miscoded proteins.
On the molecular level, your body is fighting against chaos - it sounds like an overstatement, but there is so much crap going wrong every second of every day that your body has to compensate for. It's truly amazing how well the human body can keep itself in check - I suppose we wouldn't have arrived at the level of complexity that we have today if it were not able to.
tb.
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