A closer look at the behaviour of milk lipids during digestion.

Milk has recently been reported to form complex self-assembled liquid crystalline structures during digestion by lipolytic enzymes. The formation of cubic phases at the endpoint of digestion was of particular interest as this requires a fine balance in self-assembly. This manuscript probes the robustness of the kinetic structural behaviour when milk is subjected to a range of processes that are encountered by milk and/or are relevant to the use of milk in pharmaceutical applications (homogenisation, lyophilisation, freeze-thawing and freeze-drying) using time-resolved small angle X-ray scattering (TR-SAXS). The nature of the persistent lamellar phase that occurs during digestion is elucidated using SAXS and X-ray photoelectron spectroscopy, and the interplay between the formation of structured mesophases and the evolution of particle size during digestion is determined using laser light scattering studies. This closer look at milk lipids during digestion establishes the dependence of the structural behaviour of milk on lipid composition and not processing, and clarifies the phase behaviour and kinetic effects on particle size distribution under lipolytic conditions.