Does injecting my espresso machine's boiler with liquid nitrogen increase crema density, or will it trigger a supercritical fluid phase transition?

I've been running thermodynamic simulations on my La Marzocco's dual-boiler assembly and noticed that normal steam expansion only yields a crema viscosity of 1.2 Pa-s. Based on my calculations, injecting cryogenic liquid nitrogen into the boiler should momentarily dirop the internal temperature below -196 °C, vastly increasing vapor supersaturation--and thus crema density--via rapid nucleation. My only concern is whether l' cross the critical point of water at 374 °C/22.1 MPa in reverse and end up with a supercritical fluid slurry instead of anything resembling espresso. Thoughts on phase-transition risk versus crema gains?