Impact of Pasteurization and Storage on the Microbiological Composition and Lipid Degradation of Human Milk Cream

Human milk cream, a lipid-rich fraction obtained during milk defatting, is typically discarded despite its potential for individualized nutritional strategies. This study evaluated the effects of Holder pasteurization (HoP) and storage conditions (refrigeration and freezing) on the microbiological profile and lipid stability of human milk–derived cream. Cream fractions from six mothers of preterm infants were analyzed for bacterial counts using Columbia Nalidixic Acid and MacConkey agar, with isolate identification by MALDI-TOF MS, and for lipid stability through free fatty acids (FFAs), triacylglycerol (TAGs) composition by GC-FID, and peroxide values (PV) determined by a rapid photometric method. Raw cream showed stable total bacterial counts across storage conditions, with a reduction in Gram-negative bacteria after freezing, while HoP samples exhibited no detectable bacterial growth. Lipolysis was significantly higher in raw cream, with increased FFAs after 72 h refrigeration, whereas HoP samples maintained lower and more stable FFA levels. TAG profiles remained largely stable under refrigeration but were significantly altered during frozen storage in raw samples, suggesting membrane disruption and selective hydrolysis; these changes were attenuated in HoP samples. PV increased over time in both groups, indicating progressive primary lipid oxidation, although values remained within moderate ranges. Overall, HoP improved microbiological safety and lipid stability, supporting the potential use of human milk cream as a controlled lipid source for individualized fortification in preterm infants.