This experiment, which began on March 1, 2019, should fulfill two purposes. First and foremost, to verify that my hotboxes will not produce defects in the tea. The second purpose, of much lesser importance this early on, is to note differences between young raw puer stored at 36°C and 40°C.

For this experiment, I used 2018 “Impression” from Yunnan Sourcing.

A few months ago, I ruined a number of cakes of raw puer tea in both of my hotboxes, which were set to 40°C. This was because of excess heat: My temperature sensor was placed too far from the heat source, meaning that the tea closest to the heat source was overheated. These teas were heated to around 46-49°C.

The damaged teas have a particular flavor and aroma that, at this point, I can easily identify the slightest traces of. So the natural next step with this issue is to compare 40°C to a cooler temperature, in this case 36°C, to see if it helps with the situation.

Methods

• Cake cores were removed from prior to reduce sample variation.
• Boveda packs were used to condition the samples. The generated humidity of each sample was measured separately in close-fitting mylar bags using a calibrated analog hygrometer. Once I ensured that both samples reached equilibrium moisture content within the mylar bags, I removed the Boveda packs from the bags, then zip-sealed the bags and placed them in the corresponding hotboxes to begin the 90-day storage period.
• Once the storage period was complete, I let the samples acclimate at ~22°C overnight before evaluation.

Storage Treatments

• A – Conditioned to 65% RH at 22°C, sealed in mylar without Boveda, stored at 36°C.
• B – Conditioned to 65% RH at 22°C, sealed in mylar without Boveda, stored at 40°C.

Evaluation

Brewing parameters: 1g/15mL ratio. 6.33g leaf in 95mL gaiwan. Brewed at 98°C. The samples for brewing were almost entirely unbroken leaf from the loosely-compressed rim area of the cake chunks.

36C Sample

Rinse: Surprisingly palatable. Reasonable amount of sweetness, no bitterness, no drying mouthfeel. Only a hint of that dustiness one would usually expect in a rinse. Pristine.

1. Just slightly starting to open up. Nothing off is jumping out at me.
2. The color is turning to a light yellow. Just a touch of sourness in the aftertaste.
3. Golden color, identical in appearance to 40°C. Low amount of mouth-puckering. A more pronounced sourness. Taking a whiff of the leaves still hot in the gaiwan, there isn’t a trace of sourness to be found. A great sign in this context. Not much bitterness. Astringency gradually building as expected. Not as good as the last cup, probably because I had to take a 10-minute break in between cups.
4. Better, though still not especially pleasing. There’s nothing “wrong” with it, it’s just not a superb tea. Anyway, we’re only here to examine the effects of heated storage. And so far, it’s as good as I could’ve hoped. The aroma is quite nice, by the way. My teeth are starting to feel a bit sensitive.
5. If I were describing a pair of headphones, I would say that the soundstage of the 36°C pair is narrower than that of the 40°C pair.
6. Easily enough potency to continue to demonstrate differences in comparison to the 40°C sample, but I get the idea. No need to continue, 40°C wins hands down.

40°C Sample

Rinse: Exactly the same as the 36°C sample, except with a slight prickly sensation in the mouth.

1. This cup has a slightly softer mouthfeel than from the 36°C sample. This difference is small but easily discernible. None of that unwanted prickly sensation from the rinse remains.
2. The color is more of a golden yellow compared to the 36°C sample. Once again, a smoothed out, fuller mouthfeel. A touch sweeter. Whether or not there is a detectable sourness is hard to say. What I can say, though, is that there’s a proper balance of satisfying flavor, and no defects jump out at me.
3. Golden yellow color. Just a touch of bitterness. Astringency is starting to build. Not as good as the last cup, probably because I had to take a 10-minute break in between cups.
4. Unequivocally better than 36°C cup 4. There is substantially more sweetness.
5. By this point, the colors of the brewed tea are matching very closely. Neither sample is producing a darker or lighter brew. This cup has a hint of sourness, very slight. It is overall still more pleasant than 36°C cup 5.
6. Easily enough potency to continue to demonstrate differences in comparison to the 36C sample, but I get the idea. No need to continue, 40°C wins hands down.

Summary

Both samples were free of defects after the 90-day heated storage period. The 40°C sample tasted significantly better to me, as it had less sourness, more sweetness, and a nicer mouthfeel.

Update: July 26, 2020

Upon checking on the 40°C sample, I noticed that it had been affected by heat damage. This experiment is now over.

Update: September 4, 2020

It turns out the 40°C sample was not necessarily damaged, but affected by the lemon ester note; see this post for more information. This experiment will be superseded by others.