There is one statement, which I directly have to do, when it comes to this topic: I hate if bartenders consistently tasting all their drinks! And even worse is, when the rest of the staff is also tasting. I believe that this is not professional. And why tasting? You do have verified recipes, which makes pretty much tasting superfluous. Some could argue, that fresh juices, especially lemon and lime juice aren't consistent. But I found, that lemon and lime is quite consistent, if you are selecting the same genus. But yes, other juices might be not as consistent- if you are pressing fresh orange juice, the oranges might widely vary- from sweet, to zesty and sometimes just not so great (that is why you have to try all fresh ingredients all the time before the shift and even mid-shift. For a 20 ml pour, the difference might not be that great - however if you are using such juice as filler, it makes a major difference! The perfect method would be a refractometer... But I guess that ...