Effects of biopolymers and freezing methods on ice recrystallization studied by microscopy techniques
The relationship between the ability of stabilizers to form gel-like networks, after freezing and temperature cycling, and their capacity to retard ice recrystallization in sucrose and sucrose plus skim milk powder (SMP) solutions was studied Quiescent and dynamic freezing conditions were compared. Fluorescence, Light and Transmission Electron Microscopy (TEM) techniques were used for microstructural analysis. Non-gelling systems showed, in some cases, lower recrystallization rates than gelling systems. Therefore, steric blocking of the interface caused by the gelation of the polymer is not the only mechanism of stabilizer action. An increase in microviscosity affecting the kinetics of the system is alternately proposed. Significant differences in ice content between the two types of formulations, with and without SMP, and reductions in ice content during temperature cycling in most of the treatments suggest a thermodynamic instability, complementing the kinetic retardation effect m the main mechanism of stabilizer action.