FoodBanter.com - View Single Post - One 6-minute steep vs two 3-minute steeps

DogMa

wrote:
>>And speaking of myth, just to raise the stakes: a cake of my best Pu-erh
>>to anyone who can provide some convincing science to support the
>>oft-cited "fact" that oxygen in water is critical to making good tea.
>
> Presumably, you wouldn't argue that boiling the living
> daylights out of a pot of water (let's say five minutes of hard
> boiling, to reduce dissolved oxygen) will alter the taste of subsequent
> tea brewed using it, in comparison with brewing once the water just
> reaches the temperature appropriate for your leaves?

You are conflating at least three variables here.

Most importantly, small differences in temperature near boiling can
produce a large difference in taste, especially given the usual
step-drop transferring from hot kettle to cooler pot. So the comparison
only makes sense if both tests are done at the boil, one immediately and
one after extended boiling - or after cooling the long-boiled water to
the same "appropriate" temperature as the other sample.

Secondly, extended boiling does a lot more than remove dissolved oxygen.
By forcing equilibria per Le Chatelier's principle, it enhances the
dissociation of carbonates. With CO2 gone, divalent salts that strongly
affect flavor tend to fall out of solution. The importance of this is
easy to demonstrate.

Finally, there's the putative oxygen effect. A better test for this one
would be to degas samples of nice brewing water by nitrogen sparging,
then recharge one with oxygen. This is not a completely trivial
experiment, requiring careful scrubbing of compressor oil and other
contaminants from both gases among other precautions.

Establishing meaningful controls that can help to isolate a small target
effect amid much larger noise signals is a key element in doing
meaningful research, and one very poorly understood (if even
acknowledged) by the lay public in all sorts of contexts.

-DM