Impact of pasteurization and homogenization of human milk on its gastric digestion: an in vivo study in the preterm infant
Résumé
Human milk is the ideal food for infant nutrition and optimal growth. This is especially true for preterm neonates that are preferentially fed pasteurized donor milk when their own mother milk is not available. In vitro studies have shown that pasteurization had structural and biochemical consequences on human milk digestion among which a lipolysis reduction1,2. Homogenization reduces the milk fat globule size and may restore digestive hydrolysis by increasing the surface available for enzyme adsorption. The impact of pasteurization and homogenization on the gastric digestion of human milk has never been investigated in vivo.
Our study (ClinicalTrials.gov Identifier: NCT02112331) aimed at filling this gap. It was conducted on hospitalized preterm newborns (n = 11) fed by a feeding nasogastric tube. Different matrices were compared within two independent groups: 1) raw versus pasteurized human milk; 2) pasteurized versus pasteurized/homogenized human milk. Gastric digesta were collected at 35, 60 and 90 min after meal. Gastric volume, pH and emptying rates were determined. Structural changes were evaluated by confocal microscopy and laser light scattering. Lipolysis and proteolysis kinetics were followed by SDS-Page, thin-layer and gas chromatography methods.
The study evidenced that gastric pH for raw milk was significantly lower than that for pasteurized milk at 35 min while milk homogenization did not affect postprandial gastric pH. Within the two groups, gastric emptying was strongly affected by treatments at 35 min. Although lipolysis and proteolysis presented high inter and intra-individual variabilities, they were still affected by treatments. More specifically, lipolysis at 35 and 60 min tended to be higher in homogenized/pasteurized versus pasteurized milk and proteolysis at 60 min was higher in raw compared to pasteurized milk.
This study presents a unique set of data illustrating the impact of food structure on its gastric digestion and disintegration in preterm infant newborns. These data will be useful to validate in vitro and in silico digestion models. They will improve the understanding of the human milk digestive behaviour and should help optimizing technological treatments of human milk.