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Experimental determination of pressure/temperature (pT) phase diagram of water, food models and real products at discrete pT points (-5 to -35°C and 0)

The decrease of temperature below its freezing/melting point leads to freezing of unfrozen samples at ambient and high pressure. However, to start nucleation of ice crystals supercooling is required depending on experimental conditions (cooling rate, physical properties, cooling system). Freezing of potato to higher ice modifications show a typical temperature plateau due to the exothermic thermal event when plotting temperature versus time. The degree of supercooling can be quantified by a sudden temperature increase from the nucleation to the initial freezing point.

Therefore, temperatures of nucleation and phase transition are different. The freezing point of solutions is displaced by solvents towards lower temperatures at atmospheric pressure, but only few and disperse studies are available at HP. The effect on freezing point to ice I for a range of concentrations of NaCl and sucrose has been studied.

High-Pressure Differential Scanning Calorimetry has been used to experimentally validate some of the computed results, obtain the experimental phase diagram of real products and calculate the latent heat of fusion and ice content. For tylose, partial phase diagrams were established. Singular points were obtained through pressure-assisted freezing profiles (at quasi-constant pressure), resulting in experimental points for phase transition and nucleation at different pressure levels.

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