FTIR and confocal Raman microspectroscopy were used to measure interactions between albumin and ice in situ during quasi equilibrium freezing in dimethyl sulfoxide (DMSO) solutions. At temperatures of -4 and -6 degrees C, albumin was found to be preferentially excluded from the ice phase during near equilibrium freezing. This behavior reversed at lower temperatures Instead, DMSO was preferentially excluded from the ice phase, resulting in an albumin concentration in the freeze-concentrated liquid phase that was lower than predicted. It is hypothesized that this was caused by the albumin in the freeze-concentrated liquid getting adsorbed onto the ice surface or becoming entrapped in the ice phase. It was observed that, under certain freezing protocols, as much as 20% of the albumin in solutions with starting concentrations of 32-53 mg/mL may be adsorbed onto the ice interface or entrapped in the ice phase.