Multiscale Assessment of the Effect of a Stearic-palmitic Sucrose Ester on the Crystallization of Anhydrous Milk Fat

Anhydrous milk fat (AMF) is a flavorful, but particularly complex fat containing a wide variety of fatty acids (FAs) and triglycerides (TGs), resulting in an extended melting range of -40 °C to 40 °C. The functionality of this fat can be steered by the addition of sucrose esters (SEs). In this study, the crystallization behavior of AMF in the presence of a stearic-palmitic SE was assessed. Samples were cooled at 1 °C/min (slow cooling) or 20 °C/min (fast cooling) to 0 °C, 20 °C or 25 °C and kept isothermal for one hour. At each of these temperatures, AMF was found to crystallize via different polymorphic pathways and chain length structures, as studied by wide- and small-angle X-ray scattering. The addition of the SE (0.5 wt%) accelerated nucleation and allowed crystallization to start at higher temperatures. Polymorphic transitions were accelerated, but not changed. For fast-cooled samples, ultra-small-angle X-ray scattering provided insights into the mesoscale behavior of the crystal nanoplatelets (CNPs). It was observed that CNPs formed at 20 °C were smaller than those at 25 °C. The addition of the SE did not change the size nor the shape of CNPs. Polarized light microscopy (PLM) and cryo-scanning electron microscopy (cryo-SEM) gave insight into the microstructure of the networks. Addition of the SE resulted in more fine and dense fat crystal networks at 0 °C and 20 °C. At 25 °C, large separate floc structures were encountered, with and without the addition of the SE.