Cryoprotection of Emulsions in Freeze-Drying: Freezing Process Analysis

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Abstract
We report the effects of different freeze/thawing processes on oil-in-water emulsions. The influence of the oil phase concentration, the cooling rate and the addition of carbohydrates as cryoprotectors were investigated. It appears that a slow cooling rate and the addition of cryoprotectants which do not crystallize during freeze/thawing have the best stabilizing effects. These stabilizing effects were attributed to the amorphous state of the cryoprotectants and the lower mechanical stress due to the slow cooling rate. Heat treatment before thawing causes crystallization and decreases the stabilizing effects. These results show the importance of crystalline state of additives used as cryoprotectants during freeze/thawing.