rhodes553 Senior Member Joined: 24 Feb 2005 Posts: 9 Location: Brooklyn, NY Expertise: I love coffee
Espresso: Moka Pot Grinder: Solis Maestro Plus Drip: Melitta Pour-Over Roaster: D'Amico Foods, Brooklyn
Posted Sun Mar 10, 2013, 2:38pm Subject: TDS vs. brew method
I have a perception, without doing any real side-by-side comparisons or rigorous testing, that different brew methods are quite distinct at a given TDS, and that ~1.3% TDS may not be desirable for all methods. For example, I find a high TDS more tolerable with pour-over than with siphon. Do any of you have similar experiences? Has the ~1.3% standard been researched across a variety of brewing methods?
Posted Mon Mar 11, 2013, 8:46am Subject: Re: TDS vs. brew method
If you're keeping the brew ratios the same, then yes there is a large difference between the two if you achieve the same TDS% (Strength).
At 17.4 brew ratio (grams brew water per gram of brew coffee), and a brewing system assimilation (difference between brew water and produced coffee, divided by brew coffee) of 2, the extraction will be 20%.
However, the siphon, an immersion method, at same brew ratio of 17.4, IF you achieve a strength (TDS%) of 1.30%, will be overextracted at 22.9% extraction. I wouldn't recommend it. Better to achieve this same strength (1.30%) at a brew ratio of 15.4, which would be 20% extraction.
TDS% is simply a measure of strength. The range of consumption goes from 0.85% (McDonalds) to ~1.15% - 1.6% (Assorted coffee shops), to 1.5%-2.5% (AeroPress concentration), to 3% (Moka Pot), to 5.0% (typical superauto normale espresso like you'd get in a Starbucks), to pushing 15.0%-18.0% (a coffee shop artisan 3rd wave super-tight ristretto espresso).
TDS% alone is not a good representation of anything having to do with flavor except in context of the brew ratio or yield ratio and method used to make it.
However, the range of calculated extraction normalized by the brew coffee (grams of total dissolved solids divided by the brew coffee) is still in a fairly narrow range for acceptable consumption (generally between 17% to a fairly bitter-but-people-drink-it-everyday 22%).
Siphon, French Press, AeroPress (if making straight strength comparison), CCD are all immersion/infusion/steep methods. They require a bump in brew coffee to achieve the same combination of extraction % and TDS%.
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