Food crystallization agitation

Another parameter that influences the overall properties of the bulk emulsion is the physical state of the lipid droplets in an emulsion (17, 19, 28-31). Crystallization of lipid droplets in emulsions can be either beneficial or detrimental to product quality. Margarine and butter, the most common water-in-oil emulsions in the food industry, are prepared by a controlled destabilization of oil-in-water emulsions containing partly crystalline droplets. The stability of dairy cream to mechanical agitation and temperature cycling depends on the nature and extent of crystallization in milk-fat globules. It should be noted that because the density of the phases can change as crystallization occurs, the rate at which milkfat droplets cream can be altered as droplets solidify. Emulsion manufacturers should therefore understand which factors influence the crystallization and melting of emulsified substances, and be aware of the effect that droplet phase transitions can have on the properties of emulsions. 

Many industrial processes rely on effective agitation and mixing of fluids. The application of agitators cover the areas of mining, hydrometallurgy, biol-ogy, petroleum, food, pulp and paper, pharmaceutical and chemical process industry. In particular, in these industries we find typical chemical reaction engineering processes like fermentation, waste water treatment, hydrogenation, polymerization, crystallization, flue gas desulfurization, etc [65, 21]. 

In practice, the rate of ice formation during freezing of foods is nearly always limited by the rate of heat removal. Even at a few degrees of undercooling, a considerable portion of the water can freeze, and this produces as much as 334 J of heat per g water frozen. Moreover, the system will soon become more or less solid, preventing convection and agitation. Hence the undercooling at the ice crystal surface is reduced to small values (often much below one kelvin). Linear crystallization rate then is rarely more than some micrometers per second this is, however, still fast compared to the rate obtained for crystallization of most substances from solution. 

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