To gain insight into the molecular relaxations in mixtures of structurally complex proteins in which both the intramolecular and intermolecular interactions dominate, the nature of the glass transition of vitrified beef, the crystallization of its water content, the melting of the thus formed ice, and the ice <-> water phase equilibrium have been investigated by differential scanning calorimetry (DSC) during both heating and cooling of the material at different rates from 298 to 103 K. The endothermic feature associated with the onset of molecular mobility appeared over a broad temperature range acid resembled that observed for less complex proteins, e.g., hemoglobin, myoglobin, and lysozyme (Biophys, J. 1994, 66, 249), an interpenetrating network polymer (J. Polym. Sci., Part B : Polym. Phys. 1994, 32, 683), a water-containing cross-linked polymer (J. Phys. Chem. 1990, 94, 2689), and hydrated low molecular weight poly-homopeptides (J. Phys. Chem. 1994, 98, 13780). These broad features are attributed to the onset of the availability of different configurations when thermal activation causes the populations in the configurational substates to change almost continuously with changing temperature. This is tantamount to a very broad distribution of relaxation rimes or a broad distribution of energy barriers between the various substates, which also involve R-bonded water. The remarkable resemblance between the calorimetric features of the chemically complex (and containing a mixture of proteins with other ionic and organic materials) state and that of the simpler state of pure polymers, where segments of the same molecules interact mutually with the water H-bonded to it, underscores the fact that molecular degrees of freedom involved in configurational relaxations are controlled predominantly by intermolecular barriers rather than intramolecular barriers. Water and ice coexist at a thermodynamic equilibrium at all temperatures below 273 K. : Polym. Phys. 1994, 32, 683), a water-containing cross-linked polymer (J. Phys. Chem. 1990, 94, 2689), and hydrated low molecular weight poly-homopeptides (J. Phys. Chem. 1994, 98, 13780). These broad features are attributed to the onset of the availability of different configurations when thermal activation causes the populations in the configurational substates to change almost continuously with changing temperature. This is tantamount to a very broad distribution of relaxation rimes or a broad distribution of energy barriers between the various substates, which also involve R-bonded water. The remarkable resemblance between the calorimetric features of the chemically complex (and containing a mixture of proteins with other ionic and organic materials) state and that of the simpler state of pure polymers, where segments of the same molecules interact mutually with the water H-bonded to it, underscores the fact that molecular degrees of freedom involved in configurational relaxations are controlled predominantly by intermolecular barriers rather than intramolecular barriers. Water and ice coexist at a thermodynamic equilibrium at all temperatures below 273 K.