Effects of Shear Rate Variation on the Nanostructure of Crystallizing Triglycerides

Shear flow affects the kinetics of crystallization and modifies the composition of the solid and liquid Phases obtained during crystallization. Research on the effects of shear flow on the crystallization is necessary to understand how triglycerides form crystalline structures. In this Article, palm oil, Milk fat, and milk fat triglycerides were cooled at 3 or 0.5 degrees C/min from the melt at 50 degrees C down to 17.5 or 17 degrees C and left to crystallize under a shear rate of 90 s(-1) in a Couette cell system. The shear rate was then increased to 1440 s(-1). Synchrotron X-ray diffraction patterns were captured during the crystallization process. The integrated intensity, average thickness, and average lamellar spacing of the crystalline nanoplatelets were modified by the shear rate step. Increased thickness and crystalline orientation were evident after. the shear rate step-up. Similar experiments with milk fat in a Rheo-NMR instrument provided additional information to interpret the orientation and thickness changes observed These effects of shear step-up on crystallizing fats offer new options for the industrial processing of chocolate, dairy, margarine, and shortening production, allowing more freedom for tailoring their desired crystalline nanostructures.