jpender wrote:...it's to find some measure that correlates to taste. Whether or not undissolved solids affect the taste, mouthfeel, or both is beside the point.
It's possible that using total solids as a measure would work just as well and that the reason we use TDS is because that's what the most convenient tool we have measures. If you were able to demonstrate that total solids provides a significantly better correlation to taste than TDS then you would be onto something. If you couldn't then there's no value in it.
Yes! So why market the accuracy of the refractometer? It is like marketing a 1 ppm voltage reference in a 4 digit AC voltmeter. Useful voltmeter, stupid waster of a reference.
So there are two "sets". There is Total Solids (say TS) which (ignoring water chemistry) will be EY x Dose.
And then there is TDS which is measurable with a refractometer. It would work the same way as EY but for accessible solubles only.
And then the conversion from the TS EY set to the TDS set is where I am not clear on the theoretical model on. Now it may be empirical, but in that case one must derive the numbers from a whole host of tests.
Personally I would expect VST and Atago to provide the testing they did for the conversion between the sets for peer review. Do dark roast light roasts robusta arabica humidity affect outcome?
For example, can two results be compared if the drop temp in 2 degrees off? Or does "set conversion" artifacts completely mask any real EY differences? Can we even say precision (let alone accuracy) be maintained between two different coffees? Or two different grinders?
Filtering helps make two successive measurements precise and repeatable. Does it make measuring two coffees comparable?
Scraping away (slowly) at the tyranny of biases and dogma.