“Heat Defects” – The lemon ester note.

It turns out, it’s not a defect.

A little over a month ago, I made this post on Reddit, describing an unpleasant acidic note I encountered in 40°C storage. Please read that post for context before continuing. Since making that post, there have been some interesting developments.

  1. Every tea listed in that post with “heat defects” has recovered (meaning that the sharp acidity I noticed disappeared) except for the 2019 Farmerleaf Ao Ne Me cake and the 145 day 40°C-stored 2018 Yunnan Sourcing Impression sample. The latter of which was much more heavily affected, and that would be explained by the longer heated storage period. Anyway, the fact that a lot of these teas lost the acidic unpleasantness after this period of rest should be a pretty convincing clue that raw puer can suffer jet-lag after major temperature swings. I was under the impression that jet-lag could only be caused by changes in air pressure (like during airplane transport). In the future, I’ll need to wait a month for evaluation after removing samples from heated storage.
  2. I sent some samples for Marco to taste, and he wrote a post about it on his site. He described the unpleasant acidity I encountered as a “lemon ester” note and said that it could be mold, but that my tea was not ruined either way.

Personally, for the specific use case of near-future drinking, I would still not store any of my youngest raw puer at 40°C, simply because I find the lemon ester note to be highly intrusive and unpleasant. This doesn’t mean that I want my tea to stay young forever, as Marco implied near the end of his post. I’m just highly sensitive to the lemon ester note, which so far I have been able to avoid by using lower temperatures such as 32°C and 36°C.

So, what now? Further testing, of course. I will be storing some teas at 40°C to see if they can age “through” that note over the long term.

Update: August 30, 2021

The lemon ester note occurs only with sufficient humidity. Heating a dry sample does not form the lemon ester note, or any storage note for that matter.


  1. Thank you for all your hard work in these articles. This is fascinating stuff.

    During research for my pumidor I came to learn there are so many factors that can affect puer. Articles like these help myself and others avoid certain temperature and humidity ranges.


    1. For sure. Keep in mind that this storage stuff is very dependent on the particular tea you have at hand. A number of my aged teas have improved noticeably through 40 Celsius storage in a matter of 2-3 months, as have younger teas at 32-36C in the same period of time.

      That said, I stick to the suggestion that you should avoid 40C storage for your young sheng if you plan on drinking it any time soon, provided you are sensitive to that lemon ester taste. I highly recommend testing with a wide variety of samples at different temperatures before committing any full cakes.


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