jpender wrote:No argument there. But you said that "tds alone is by far more useful than tds and suspended solids" and that's what I was questioning. It makes sense that TDS alone would be the better choice versus total solids but it could be that in practice it doesn't actually make much difference.
It's probably oftentimes close, especially with espresso where your sediment is pretty minimal, but occasionally breaks down entirely giving nonsense always 100% answers for certain brewing methods like Turkish or cupping.
AssafL wrote:I may have confused some terms. I thiught extraction was "the part of the puck that found itself in the drink" and extraction yield was that expressed as percentage.
What you are suggesting is that the particulate and oils are not part of the extraction. (I originally thought the part that participates is the percolated part or the dissolved part and had nothing to do with extraction).
So why dehydrate pucks and coffee? Wouldn't a dehydrated coffee leave the particulates to give an erroneous EY since it includes stuff that wasn't "extracted" via the extraction process?
Exactly. Particulate and oils are very much part of the coffee, but not of extraction, the process of the water dissolving the soluble parts of the coffee. The sediment and oils get moved mostly as they were. Neither fat or cellulose is water soluble, so isn't going to undergo any process with a gradient of quality like the dissolved solids do, but just being carried down as is.
Drying pucks is a good way to get total yield if done properly (controlled enough to not let evaporation carry away anything), and you can probably track relative extraction at least decently for internal use, but you won't know how much of the soluble part of the coffee specifically got removed from the puck that extraction yield through tds tells you. It's also generally less useful since you're not pinpointing the thing responsible for over or under extraction, or the only part you have real direct control over. Although sharing both extraction yield and total yield would be more descriptive to convey the experience. But if my difference between total yield and extraction yield doesn't match yours, I'm probably not dialing in to it unless I have a roller mill I can set to make X particles under Y and a dosing system that strategically positions them in the basket so the right amount get through the holes. It's like sharing your drink's pH. It probably effects taste somewhat, but if you can't control it, why bother measuring it?