Modeling of a two-regime crystallization in a multicomponent lipid system under shear flow

Area of Science:

• Food Science
• Materials Science
• Physical Chemistry

Background:

• Milk fat triacylglycerols are complex lipid systems.
• Understanding their phase transitions is crucial for food processing.
• Shear can influence crystallization kinetics in lipid systems.

Purpose of the Study:

• To investigate the effect of shear on milk fat triacylglycerol crystallization kinetics.
• To analyze phase transitions under varying temperatures and shear rates.
• To evaluate the applicability of existing crystallization models.

Main Methods:

• Studied milk fat triacylglycerols in a Couette cell under shear.
• Utilized synchrotron X-ray diffraction to capture 2D diffraction patterns.
• Applied temperatures of 17, 17.5, and 20°C with shear rates up to 2880s⁻¹.

Main Results:

• No shear effect on the initial onset time for phase alpha crystallization.
• Shear reduced onset time in the first crystallization regime, consistent with the ODE model.
• A second regime showed diffusion-controlled kinetics (square root dependence) not described by the ODE model.
• Increased shear promoted crystallization of higher melting fractions, altering crystallite composition.

Conclusions:

• The ODE model is applicable to the initial shear-influenced crystallization regime of milk fat.
• A distinct, diffusion-controlled growth regime occurs as milk fat approaches equilibrium.
• Shear rate influences the composition of crystallites by promoting higher melting fractions.