Lipid droplets coated with milk fat globule membrane fragments: Microstructure and functional properties as a function of pH

Processed lipid droplets coated by milk fat globule membrane (MFGM) material are of primary interest to mimic the specific functions provided by the fat globules in milk and dairy products. The objectiveswere to investigate, as a function of pH, the properties and microstructure ofMFGM-coated lipid droplets preparedwith an ingredient rich in MFGM containing polar lipids and proteins. The samples were prepared in water and in milk ultrafiltrate. The combination of microscopy techniques, zeta potential and particle size measurements, and rheological determinations was used.We showed that all the components of the ingredient were highly sensitive to pH. Both the polar lipids and proteins contributed to the isoelectric point of the MFGM-rich ingredient at pI=4.2. Lipid droplets were coated withMFGMfragments both adsorbed at the surface of fat and protruding in the aqueous phase. BelowpH 5.5 the microstructure of the emulsions was affected by aggregation of the lipid droplets and formation of a gel. Theemulsions prepared inwater did not showcoalescence upon 30 days storage,while those prepared in milk ultrafiltrate showed coalescence for pH below 5.5. This study demonstrates that the MFGM-rich ingredient has excellent emulsifying properties and will contribute in the development of emulsions containing MFGMcoated lipid droplets for techno-functional, nutritional and health benefits (e.g. in infant formulas).