drying a cake that is too damp

Puerh and other heicha
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John_B
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Mon Jul 18, 2022 11:46 pm

This is definitely an unusual context, since I first tried sheng and shu a decade ago, and bought cakes of both back then, and never encountered it before. I recently tried a Thai wild origin cake version that seemed too damp to me, not dried properly. It was a very newly produced version, almost certainly made within a month of me getting it. I mentioned this online elsewhere but didn't write about the part about trying out drying it in a blog post (I write a blog), so there's really no connection to that writing context, beyond describing its initial character there, which I just did. I did describe taste aspects and such there, which isn't completely relevant anyway. It was really good, unusually pleasant and distinctive, but I suspect inconsistent processing by small batches could have added complexity at the cost of perhaps offsetting long term aging potential.

The tea was pliable, tightly pressed (not a concern), but not the same leaf texture as any of the range of other sheng I ever tried, apparently a bit damp. I tried drying it out, concerned that it might not age properly, that it might go sour or mold. How would you go about that? I dried some salt, about an eighth of a cup of it maybe, not much, but vastly more than would be held in a desiccant packet. My thinking was that salt conditioned to be as damp as normal local humidity level would hold no more water, so I needed to use a dried version. Then I put the two small cakes, 400 grams in total, with that into a food grade Lock and Lock container, with the salt in a small steel bowl, covered with a tissue, held by a rubber band. I checked it after a day, then went out of town for awhile, 5 days, and left it there over that time. Two air exposure instances from the humid room air would buffer the effect of drying, since the salt would end up holding that humidity first.

Of course it seemed drier later, but not necessarily bone dry (not that I could probably judge that, relative humidity level). I brewed some again, trying it for the third or fourth time, and it didn't seem much different, but leaf texture wasn't as pliable. Being stored now with the rest of my tea, in ziplock bags to limit air contact some, but allowing for plenty of exposure, will let it equalize with other tea level and normal local humidity. Which is high; I live in Bangkok, and I'm being heated and steamed here every day of the year, as that tea is.

At a guess the risk of that cake going off or growing mold was low anyway; it was probably extra damp but that would've evened back out soon enough. I'll never know, unless I hear of someone else's experiences with the same tea, or from that vendor. I wouldn't have considered it as much of a risk except that I've heard of another Thai producer ruining a batch of tea for not drying it sufficiently, made into tuochas instead, which I never heard clear details about.

I guess the point here is sharing an unusual experience, which may or may not lead to further interesting discussion.
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debunix
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Tue Jul 19, 2022 11:26 pm

This post makes me think back to analytical chemistry in college, when we were drying out chemical compounds in a special oven and very precisely measuring the weight loss through the drying process in order to determine something or other…… Did you weigh the cakes before an after to see whether they lost weight?
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pedant
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Wed Jul 20, 2022 12:23 am

or weigh the salt before and after to see if it absorbed water
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pedant
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Wed Jul 20, 2022 12:25 am

fyi you could do a salt pack thing. it will continue to absorb water from the air as long as there is some undissolved (solid) salt in there. but plain, dry salt will also work fine.

another thought: how do they dry cakes normally after making them? don't they just leave them to dry on racks after pressing? maybe you're overthinking this a little.
John_B
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Wed Jul 20, 2022 1:22 am

I didn't weigh the salt or the cakes; that would've made sense.

there could easily be a range of different answers about how producers dry cakes after pressing them, and then how they did it. processes probably depend on scale and type of processing equipment involved. I'll never really know if all of this was unnecessary messing around, if it saved the cakes from becoming ruined, or if it affected them negatively instead. all those seem possible.

the leaves were pliable in the pressed cake form; they weren't dry and brittle enough to separate out as they normally do, either separating in a twisted form, or shattering a bit when pressed to more of a brick. it felt a little like working with the wrapped rubber strands inside a golf ball, if that's familiar. even though it seemed clear the tea was more moist than normal I still don't know if it was fine for storage and gradually drying further, or not. since I think this was the first tea that producer had ever pressed I'm not sure they knew either.
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pedant
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Wed Jul 20, 2022 4:13 pm

John_B wrote:
Wed Jul 20, 2022 1:22 am
I'll never really know if all of this was unnecessary messing around, if it saved the cakes from becoming ruined, or if it affected them negatively instead. all those seem possible.
yeah, hard to say if messing with it was good, bad, or didn't matter. i wouldn't worry about it. :)

this may or may not be interesting or useful, but...

as you probably know, if you seal tea in a container at a given temperature, the air and tea will come into moisture equilibrium. the RH in the container is a reflection of the tea's equilibrium moisture content (EMC = mass of water in tea / mass of dry tea).

here are some sorption isotherms from Demystifying Silica Gel (Weintraub, 2002):

EMC-RH Isotherm (Weintraub)
EMC-RH Isotherm (Weintraub)
EMC-RH Isotherm (Weintraub).png (66.63 KiB) Viewed 2812 times

anyway, if you put the tea in a sealed container with a hygrometer and let it come to equilibrium at your typical storage temperature, you can indirectly observe its moisture content and also come to some conclusions like:
  • "this might have more/less EMC than another tea i tested"
  • "does the RH seem too high? if it's 80% or something, it might mold. especially with poor air exchange."
John_B
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Wed Jul 20, 2022 9:44 pm

This process and steps like testing humidity or thinking to check moisture removal would be more familiar if I was regularly conditioning cakes, the process would be familiar and I'd have related equipment handy. I don't, because if they're a little dry I store them in natural local humid conditions, the same as if they seem optimum. This is the first time a cake has seemed too damp to me.

It makes me wonder if one theme I've encountered of some local teas seeming sour wasn't really about improper drying, instead of a plant-type input. It has been infrequent but also consistent, so I thought it was a local aspect character, but it could be that a few producers consistently make the same mistake.
Koveee
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Thu Jul 21, 2022 6:04 am

Hi, maybe you can post some photos of cake for us?). I have interest how it looks like. In my opinion abundance of moisture in cake maybe produced mistake or features of raw material from wild location. Besides, tea can be too young for you taste and storaged in high moisture surroundings in Thai.
John_B
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Wed Jul 27, 2022 5:06 am

Even in person it's difficult to see that it looks different related to the leaf texture definitely being wet and pliable (before I dried it out). There are cake and separated leaf images in this post:

http://teaintheancientworld.blogspot.co ... sheng.html

I've tried fairly new wild-origin teas before, as pressed cake versions, and they weren't like this. Another Thai tuocha supposedly had similar issues, not from this producer, but I think the version I tried of that tea wasn't the one that someone was claiming was too damp.

I've never noticed any variation in a tea cake that related to it being damp, or even too dry, beyond rest and conditioning changing brewed character, so nothing to do with actual feel of leaves while separating them. These leaves were very pliable, so it definitely had an unusual feel.
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