Crystal structures and morphologies of fractionated milk fat in nanoemulsions

The triacylglycerol (TAG) crystal structures and morphologies of fractionated milk lipids in nanoemulsions were investigated at 4°C. Droplet size (0.17 versus 1.20 μm), lipid composition (stearin versus olein) and cooling rate (1 versus 10°C min(-1)) had an influence on the structural properties. Five crystal polymorphs (α, β'1, β'2, β1, and β2) were formed with either triple and/or double chain length structures in the solid phases of the emulsified systems. X-ray scattering peak intensities were reduced with the nanoemulsion particles. The internal structure of TAG exhibited stacking of individual lamellar layers (3.8-4.2 nm). Various anisometric shapes of fat nanoparticles were formed due to a highly sharp curvature of the nano-size droplets. The shape of olein nanoparticles was more polyhedral compared to the stearin. TAG crystals arranged in a planar-layered organisation at the slower cooling rate. These differences imply that the nanometric confinement of oil droplets modifies the fat crystal habit.