Impact of manufacturing processes on glycerolipid and polar lipid composition and ultrastructure in infant formula.

• Application of structured illumination microscopy to examine milk ultrastructure. • Pasteurization significantly impacts PC and SM in the outer membrane. • Heat treatment reduces glycerolipids with AA/DHA and glycerophospholipids. • Addition of phospholipids and freeze-drying enhance polar lipid content. • SIM effectively displays nanoscale changes in fat globules during processing. The introduction of exogenous lipids in the production of infant formula induces significant alterations in milk lipid composition, content, and membrane structure, thus affecting the lipid digestion, absorption, and utilization. This study meticulously tracks these changes throughout the manufacturing process. Pasteurization has a significant effect on phosphatidylcholine and sphingomyelin in the outer membrane, decreasing their relative contents to total polar lipids from 12.52% and 17.34% to 7.72% and 12.59%, respectively. Subsequent processes, including bactericidal-concentration and spray-drying, demonstrate the thermal stability of sphingomyelin and ceramides, while glycerolipids with arachidonic acid/docosahexaenoic acid and glycerophospholipids, particularly phosphatidylethanolamine, diminish significantly. Polar lipids addition and freeze-drying technology significantly enhance the polar lipid content and improve microscopic morphology of infant formula. These findings reveal the diverse effects of technological processes on glycerolipid and polar lipid compositions, concentration, and ultrastructure in infant formulas, thus offering crucial insights for optimizing lipid content and structure within infant formula. [ABSTRACT FROM AUTHOR]