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Poster De Conférence Année : 2018

Differences in composition and structure between human milk and infant formula: do they affect their digestion?

Résumé

Despite all the efforts made by the dairy industry to develop infant formula (IF) mimicking the composition of human milk (HM), some major differences remain between these two foods in terms of composition (nature of proteins and lipids, oligosaccharide, microbiota…) and structure (casein micelle, milk fat globule). Do these compositional and structural differences affect the behavior of the 2 products when they enter the gastrointestinal tract of the neonate? The answer is yes. For instance, gastric emptying half-time is 54 min for HM and 80 min for IF resulting in major differences in the kinetics of hydrolysis of proteins and lipids. This presentation will summarize ten years of work conducted at INRA on food digestion leading to the release of more than 40 peer-reviewed articles. First, gastrointestinal digestion of HM and IF was compared using a dynamic in vitro digestion simulator, the DiDGi®. Caseins were shown to be more extensively broken down in the stomach in IF than HM. In contrast, HM lipids were more degraded in the stomach due to the action of the milk endogenous lipase but were less hydrolyzed in the small intestine. This difference was attributed to the homogenization process applied to IF transforming large milk fat globules into smaller lipid droplets and increasing the specific surface available for digestive lipases. In a clinical trial performed on pre-term neonates, the effect of pasteurization and homogenization of HM on the kinetics of gastric lipolysis and proteolysis was investigated. Pre-term neonates were fed through a naso-gastric tube that also allowed to aspirate their stomach content at different post-prandial times. Pasteurization was shown to decrease the resistance of lactoferrin that was hydrolyzed faster in the stomach. Homogenization led to an acceleration of lipolysis in the stomach of the pre-term neonates. In a third project, the effect of the heat-treatment applied to IF manufacture on the casein resistance to gastrointestinal digestion was investigated. Model IF were developed at a pilot plant scale and the effect of 4 heat treatments applied to the protein concentrates (no heating, 80°C/20s, 85°C/3 min, 105°C/60s) on casein digestion was studied. Casein domains carrying post-translational modifications and hydrophobic areas were shown to be the most resistant to the digestive process. The intensity of the heat-treatment was shown to dramatically affect casein resistance to digestion; the more IF were heated, the more resistant the casein were. This resistance was attributed to the thermal aggregation of whey protein that were forming a protective layer around the casein micelle. Finally, IF were designed at INRA’s dairy platform and their in vivo digestion by piglets investigated. IF1 was a control IF with vegetable oil and milk proteins at the interface of the lipid droplet. In IF2, lipid droplets were stabilized by milk phospholipids in order to recreate a structure close to that of the milk fat globule. Finally, IF3 was also stabilized by milk phospholipids and 60% of the vegetable oil was replaced by milk fat. Piglets were fed 28d with one of the three IF. Concentration of caseins and -lactoglobulin in the jejunum and ileum was higher for IF3. Higher intestinal thickness was also observed with IF3 but was not associated with changes in permeability. IF3 increased IFN secretion suggesting an improved intestinal immune system maturation such as observed in sow suckling piglets. Finally, the nature of IF was shown to dramatically affect the intestinal microbiota composition of piglets. All these data show that IF still exhibit major differences with HM affecting their kinetics of disintegration in the GI tract. Designing a new generation of biomimetic IF is an objective that we are currently trying to reach.
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Dates et versions

hal-02011378 , version 1 (07-02-2019)

Identifiants

  • HAL Id : hal-02011378 , version 1
  • PRODINRA : 459111

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Didier Dupont, Olivia Ménard, Amélie Deglaire. Differences in composition and structure between human milk and infant formula: do they affect their digestion?. 15. International Symposium on Milk Genomics and Human Health, Nov 2018, Sacramento, United States. , 2018. ⟨hal-02011378⟩
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