Crystallization - of solids from solutions or alloys is a mass transfer process based on the transfer of matter between two contacting phase surfaces. That is, it is a phase transition that occurs when a substance passes from a solution (liquid phase) to a crystallized product (solid phase). During the crystallization process, impurities (impurities, impurities) present in a certain amount in working solutions, including sucrose solutions, are always separated from the crystalline product (crystallization).

The crystallization process can occur only in supersaturated (supersaturated) solutions. Therefore, the formation of crystallization centers and their growth is possible only if the thermodynamic potential of pure sucrose crystals at the end of the process is lower than before the start of crystallization. The driving force of the sucrose crystallization process and the main factor determining the crystal growth rate is the concentration difference between two immiscible phases - that is, the substance in the supersaturated solution (a solution with a concentration higher than the equilibrium concentration of this substance at a given temperature) and the substance on the crystal surface.

The crystallization of sucrose from saturated sugar solutions, which occurs in vacuum apparatuses (including those operating cyclically), is a physicochemical process, a very complex heat exchange process and can be influenced by various factors - for example, the concentration of the solution at a certain time, the temperature ranges, and the residual pressure in the vacuum apparatus. These factors can be described by the corresponding dependencies (i.e., mathematical relationships). The crystallization process of sucrose fully enters the second stage of crystal growth only when the crystallization centers capable of growth "solidify" and the growing crystals reach a certain size. Simultaneously with the crystallization process of sucrose, its decomposition under the influence of high temperature also occurs. In addition, in parallel with the crystallization of sucrose, various by-products are formed as a result of the interaction of reducing sugars, coagulation or decomposition of organic compounds (non-sugar substances), as well as the crystallization and recrystallization reactions of sucrose.