Résumé
Human milk is the ideal food for infant nutrition and optimal growth. This is especially true for preterm neonates that are preferentially fed donor milk when their own mother milk is not available. For sanitary reasons, donor milk is pasteurized. This may have structural and biochemical consequences on the maternal milk emulsion and affect digestive kinetics. This has been rarely investigated. Thus that was the aim of our study. Mature human milk was collected over 2 days and stored at +4°C. Half of it was digested as is (fresh milk). The other half was frozen (-20°C, 5 weeks) and pasteurized (62.5°C, 30 min) prior digestion. An in vitro dynamic system was used to simulate the gastric and intestinal digestion phases of a 1-month old newborn. Structural changes of digested samples were evaluated by confocal microscopy and laser light scattering. Proteolysis and lipolysis were monitored over 180 min. Hydrolysis kinetics were followed by SDS-PAGE and Thin-Layer Chromatography methods, followed by densitometry for semi-quantitative estimations. Pasteurization impacted the emulsion structure by increasing the protein susceptibility to acid aggregation especially on the milk fat globule membrane (Fig. 1). In the gastric compartment, we observed a faster hydrolysis of caseins (κ, β) and lactoferrin in pasteurized milk than in fresh milk (X 2 at 30 min). At 120 min, virtually all proteins were digested in pasteurized milk, whereas approximately 55% of proteins were undigested in fresh milk. In the intestinal phase, most proteins were digested during the first 30 min. Lactoferrin was more resistant in fresh milk than in pasteurized milk. Similarly, lipids were digested faster in pasteurized than in fresh milk, but to a lesser extent than proteins. These results demonstrate that pasteurization increases the rate of proteolysis and lipolysis. The physiologic and metabolic impacts remain unknown, especially in newborns exclusively fed pasteurized milk.