NewBoyUK When you say ‘set up’, do you mean adjust grind for a known brew method/ratio/system? (E.g. 1:2, or other known/typical ratio espresso shots, or filter brews?
You would be able to nominally dial in to a target %EY (maybe 19% +/-2% for espresso, or 20% +/-2% for filter), within a handful of grind adjustments. This would not, in itself, guarantee a great tasting result, but it would show there is no obvious objective, mechanical impediment in the owner/user then fine tuning to their preference point.
The target range is typically 18-22%EY, but different roasts and origins extract more/less than each other, Brazils, Costa Ricans & Guatemala may taste best at the lower end, Kenya, Rwanda, Colombia at the higher, you can still get under extracted coffee at 19% and over-extracted at 21%, in terms of sensory perception depending on the bean. A 20% extraction, for example, would be an average target over a sample, not the best target in a ‘one size fits all’ scenario.
I don’t really see the use for roasters specifically, they tend to brew/QC by cupping & rarely measure the dose (if SCA protocol), nor the water weight, frequently under-extracting coffee. You can under-develop roasts (in the sensory aspect) and still achieve an expected EY, To roast coffee so badly that it doesn’t normally extract in a filter brew would show a catastrophic failure & be pretty tragic (nevertheless it occasionally happens).
In short, if the machine & grinder are known good models, without any obvious/detectable malfunctions and the coffee is ball-park roasted for the brew method (e.g. very light/filter roasts may need to be brewed at longer espresso ratios to satisfactorily extract), you’re probably not going to see any evidence of a problem that isn’t already presenting a clue elsewhere, like way too coarse/fine a grind, someone trying bizarrely short espresso ratios etc.
If you always took a bean with you, that was consistently available and you were used to it, you could use this to dial in and say, ’I tested with my usual beans, dialled in & all is working well. ’If the customer says that they don’t like their beans with the set up you could tell in a brew whether there was an obvious extraction related reason why, if not then tell them to buy different beans :-) Beans are an ingredient, we buy different ones to explore different tastes, sometimes we just don’t like them when brewed normally. You can’t fix every bag by tweaking extraction. You are dealing with objective mechanical devices, you can use a refractometer to check their objective function, You can’t make everything taste great, in the same way you can’t fix someone’s CD player to make Tom Waits sound like Elvis.
