If it wasn't a caffeine emergency, I would have just tossed this one. Most sour and acidic shot of espresso I can remember.
Guessing it was a severe underextraction. I watched the barista process and nothing seemed off. It's an excellent Marzocco machine they have. So might just need tuning or the dosage if off. Only other thing I can thing is a batch of extremely underroasted beans.
I'm back here at Boston University next week for a VERY long meeting so perhaps I will give it anotehr try.
Cupping Method:Doppio at Pavement BU location, Marzocco Strada 3