Intuit wrote:I considered this possibility, that steaming would halt microbial fermentation.
Aren't most iron cakes that require steaming tuocha? Small mass heavily pressed cakes probably age very slowly anyway, because of low oxygen conditions in the cake interior.
Lightly steaming, drying and storing in an airy location to mellow the flavor means that you will be consuming the tea within months or a year.
So, maybe it doesn't matter.
I should clarify (or correct myself) that prolong exposure to steam above 60C would kill microbes in tea cake. Dry Pu-Erh tea leaves were steamed and soften before compressed into brick/cake form. The duration of steaming/compressing process is short. I think using steam to loosen a compressed tea cake/brick would take much longer and temperature on surface of tea cake rises above 60C and kill some microbes.
For your reference, I found a few videos on Pu-Erh tea cake manufacturing process from
Ancient Tea Horse Road.
Microbial fermentation works better on a compressed tea cake than loosen tea leaves, as microbes would propagate to entire compressed cake but not on loosen tea leaves. I am not a microbiologist, so I can't explain exactly how it works.
My experience is that some of my (compressed) tea cakes are going through flavor change process, but loosen tea leaves/blocks from the same tea cake that I broke apart a year ago don't. Also, I have some aged loose leaves Pu-Erh and its flavor doesn't change much (only smoother and less bitter, but minimal or no flavor change).
So, assuming microbes survive steaming process, once tea cake is broken apart, microbial fermentation will be regional and I don't expect its flavor will change over time.
Iron cakes are highly compressed and notoriously known for their hardness (and I heard many bloodshed stories when disassembling them). Yes, its aging process would be slower than tea cakes under the same storage environment. Some people see this property is positive as they can taste different flavor from surface and inner core (due to different aging speed). The bounding (glue like) in iron cakes would break down overtime just like tuocha and other tea cakes/bricks and this would make them easier to break apart after years of aging. I have a few mid 1980 tuocha's and they are very easy to break apart (much easier than some tea bricks/cakes).
Never try steaming tea cakes, since most my cakes/bricks are fairly easy to disassemble/break. So, my comments on flavor change after steam are speculative.
Not sure about mellowing the flavor. At least for aged Shu, I don't expect its flavor becomes mellower after (lightly) steamed. This might be the case for young Sheng and young Shu, as steam might tone down its bitterness or "wodui" odor. Some people even go as far as baking tea leaves before brewing (similar to re-bake for Oolong and brewing method used by Yunnan Lahu) to improve its flavor. Don't know if that works (in improving flavor) though.
Anyway, this is a very interesting topic. Hope you find something useful.
