Wait, so how do you tell the difference between sour from low temp and sour from beans that are too fresh? Is it just a taste thing or are there other signs?
Oh man, I gotta respectfully disagree with dakota_miller93 on that one. In my experience (and I've pulled a lot of sour shots, trust me), fresh beans usually give me that sharp, vinegar-like tang, while low temp sour is more of a muted, flat kind of acidity. But I'd bet the real test is just bumping the temp up a few degrees and seeing if that rounds out the flavor, fresh beans or not.