Development of a Fluidized-Bed Crystallizer for Wine Treatment.

In addition to sugar, grape berries accumulate both tartaric acid and potassium during ripening. While the concentration of these compounds and their salt, potassium bitartrate, may be within solubility limits of grape juice at maturity, the solubility limit of potassium bitartrate is often exceeded in finished wine. This is due to a reduction in solvent polarity effected by the presence of ethanol as well as any supplemental tartaric acid additions or pH adjustments by the winemaker. Depending on the temperature and duration of storage, precipitation of potassium bitartrate crystals can therefore occur in wines subsequent to bottling. To the uninformed consumer or retailer, the appearance of such crystals can be perceived as unnatural and an indication of poor winemaking. He may even discard or return the bottle for fear that the crystals are ground glass. Consequently, most wineries promote the crystallization of the supersaturated portion of potassium bitartrate in wine prior to bottling through a process known as cold stabilization. The purpose of this research effort was to develop an improved method for performing the cold stabilization of wine using a fluidized—bed crystallizer. The proposed process is intended to provide reduced time and energy requirements, as well as greater control over the certainty and extent of crystallization, relative to current commercial practices. The scope of the present study was limited to bench—scale testing of a fluidized-bed crystallizer and the evaluation of mathematical models for both fluidization and crystal growth kinetics.