I've been struggling with a new problem and can't find anything with a forum search. It's somewhat backwards from the norm of crappy straight espresso that is masked by milk. Ive been pulling some very nice, balanced shots of Klatch WBE and Mocha Java. The straight shots are fruity with a bright start and a nice chocolate finish. However, when I put those same shots in milk, I'm getting a biting bitter finish that I'm not liking. It's a newer problem for me and my milk hasn't changed.

Without getting into the nuances of how I'm pulling the shots, are there any broad explanations for why a good tasting and balanced shot would become a bitter sinker once added to milk?

I have two hypotheses. 1) Bitter is a potent flavor that seems to persist more than others as a beverage is watered down. 2) Adding sugar to a drink can often make me perceive bitter more by simple contrast, and milk brings considerable sugar to the party. Many of our senses as tuned to find and amplify contrasts.

I have nothing but speculation to back up these thoughts, but you might test it out by making an Americano, or adding sugar to the espresso (or both). Report back if you find something interesting =D.

Ok, it seems to be a strange sweetener interaction. Straight espresso is good and on the bright side. Add steamed milk without sweetener and it's a nice and unsweetened latte. Add one Splenda and it's a bitter nasty. Add in a single Truvia and we're back to balanced latte but now nicely sweetened. The Splenda is doing something weird.

Have you tried skimming off the crema before adding the milk?

And destroy my latte art? LOL. I may give it a try. I've mixed it all together before drinking. The bitterness is more of a global deeper character in the after-taste. Not the kind of tip of your tongue taste that you get by sipping only crema while not getting enough beverage.

It's no mystery that latte art makes a milk drink more bitter. stir it before drinking and see if it helps.

Some, but not gone. I'm going back to some of my tried and true blends to make sure I can recreate those.