The world of milk is an interesting one. Until I got involved in compeition I had no idea how complex and varying the qualities of milk are based on their nutritional sources and processing. It's amazing to taste milk as it shapes your coffee for capps and becomes a tool of texture and taste symmetry. However, bad milk is more than capable of derailing an otherwise wonderful coffee experience.
The other day I was in a hurry to catch my shift at the bar I work at. I stopped by the Meijer grocery store to pick up a half gallon of my favorite organic milk, but because I was in a such a rush I ended up grabbing milk slightly out of date. Not realizing this, I poured an afternoon capp for myself and fellow employee and sat down for a moment. When I first sipped what I expected to be a rich, buttery drink was instead much like a raw piece of salmon being raked across my tongue! I figured at first that it might've been some fluke with the cup being dirty or something of the sort and went to pour yet another. This yielded the same results.
I promptly returned the past date milk and have now returned to a state of coffee enjoyment. Having experienced that I am amazed at how little detail is shown in milk selections in many coffee bars I know. My friends at MadCap in MI spent days going through multiple dairies and even different process types before they found the milk for them. The coffee is valuable and the milk added to it should show that.