Impact of pasteurisation on the digestion of human milk as simulated in an in vitro dynamic system
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 kinetics of digestion and
disintegration of the emulsion in the digestive tract of the newborns. This has been rarely
investigated, thus that was the aim of our study.
An in vitro dynamic system was used to simulate the gastric digestion phase of a 1-month old
newborn [1,2]. A pool of mature human milk (n = 5 donors) was digested as raw or
pasteurised (holder pasteurisation: 62.5°C, 30 min), triplicate digestions. Structural changes of
digested samples were evaluated by confocal microscopy and laser light scattering. Lipolysis
and proteolysis were monitored over 120 min. Hydrolysis kinetics were followed by SDSPage,
thin-layer and gas chromatography methods, followed by densitometry for semiquantitative
estimations.
Pasteurization impacted the emulsion structure by increasing the protein susceptibility to acid
aggregation especially on the milk fat globule membrane. Structure of fat globule was
maintained during gastric digestion mainly in pasteurised human milk. Lipids were digested
faster in raw than in pasteurised milk. In the end of the gastric phase, less triglycerids and
more free fatty acids were observed for raw milk (p<0.001). At 120 min of digestion, similar
levels of global proteins were observed. However, we observed a faster hydrolysis of casein-β
in raw milk and of lactoferrin in pasteurized milk.
These results demonstrate that holder pasteurisation of human milk modifies its digestive
kinetics in the gastric phase, as simulated in an in vitro dynamic system. The physiologic and
metabolic impacts remain unknown, especially in newborns exclusively fed pasteurized milk.