Florence Rousseau

Impact of pasteurization of human milk on preterm newborn in vitro digestion: Gastrointestinal disintegration, lipolysis and proteolysis

Human milk feeding is an important recommendation for preterm newborns considering their vulnerability and digestive immaturity. Holder pasteurization (62.5°C, 30min) applied in milk banks modifies its biological quality and its microstructure. We investigated the impact of pasteurization of preterm human milk on its gastrointestinal kinetics of lipolysis, proteolysis and structural disintegration. An in vitro dynamic system was set up to simulate the gastrointestinal digestion of preterm newborns. A pool of preterm human milk was digested as raw or after Holder pasteurization. Pasteurization impacted the microstructure of undigested human milk, its gastrointestinal disintegration and tended to limit the intestinal lipolysis. Furthermore, the gastrointestinal bioaccessibility of some fatty acids was decreased by pasteurization, while the intestinal bioaccessibility of some amino acids was selectively modulated. The impact of pasteurization on the digestion of human milk may have nutritional relevance in vivo and potentially modulates preterm development and growth.

Lipid droplets coated with milk fat globule membrane fragments: Microstructure and functional properties as a function of pH

Processed lipid droplets coated by milk fat globule membrane (MFGM) material are of primary interest to mimic the specific functions provided by the fat globules in milk and dairy products. The objectives were to investigate, as a function of pH, the properties and microstructure of MFGM-coated lipid droplets prepared with an ingredient rich in MFGM containing polar lipids and proteins. The samples were prepared in water and in milk ultrafiltrate. The combination of microscopy techniques, zeta potential and particle size measurements, and rheological determinations was used. We showed that all the components of the ingredient were highly sensitive to pH. Both the polar lipids and proteins contributed to the isoelectric point of the MFGM-rich ingredient at pI=4.2. Lipid droplets were coated with MFGM fragments both adsorbed at the surface of fat and protruding in the aqueous phase. Below pH5.5 the microstructure of the emulsions was affected by aggregation of the lipid droplets and formation of a gel. The emulsions prepared in water did not show coalescence upon 30days storage, while those prepared in milk ultrafiltrate showed coalescence for pH below 5.5. This study demonstrates that the MFGM-rich ingredient has excellent emulsifying properties and will contribute in the development of emulsions containing MFGM-coated lipid droplets for techno-functional, nutritional and health benefits (e.g. in infant formulas).

Impact of homogenization of pasteurized human milk on gastric digestion in the preterm infant: A randomized controlled trial

BACKGROUND & AIMSnIt has been suggested that homogenization of Holder-pasteurized human milk (PHM) could improve fat absorption and weight gain in preterm infants, but the impact on the PHM digestive kinetics has never been studied. Our objective was to determine the impact of PHM homogenization on gastric digestion in preterm infants.nnnMETHODSnIn a randomized controlled trial, eight hospitalized tube-fed preterm infants were their own control to compare the gastric digestion of PHM and of homogenized PHM (PHHM). PHM was obtained from donors and, for half of it, was homogenized by ultrasonication. Over a six-day sequence, gastric aspirates were collected twice a day, before and 35, 60 or 90xa0min after the start of PHM or PHHM ingestion. The impact of homogenization on PHM digestive kinetics and disintegration was tested using a general linear mixed model. Results were expressed as meansxa0±xa0SD.nnnRESULTSnHomogenization leaded to a six-fold increase in the specific surface (Pxa0<xa00.01) of lipid droplets. The types of aggregates formed during digestion were different between PHM and PHHM, but the lipid fraction kept its initial structure all over the gastric digestion (native globules in PHM vs. blend of droplets in PHHM). Homogenization increased the gastric lipolysis level (Pxa0<xa00.01), particularly at 35 and 60xa0min (22 and 24% higher for PHHM, respectively). Homogenization enhanced the proteolysis of serum albumin (Pxa0<xa00.05) and reduced the meal emptying rate (Pxa0<xa00.001, half-time estimated at 30xa0min for PHM and 38xa0min for PHHM). The postprandial gastric pH was not affected (4.7xa0±xa00.9xa0at 90xa0min).nnnCONCLUSIONSnHomogenization of PHM increased the gastric lipolysis level. This could be a potential strategy to improve fat absorption, and thus growth and development in infants fed with PHM; however, its gastrointestinal tolerance needs to be investigated further. This trial was registered at clinicaltrials.gov as NCT02112331.

Ser2 from Serratia liquefaciens L53: A new heat stable protease able to destabilize UHT milk during its storage

The heat-stable protease Ser2 is secreted by the species Serratia liquefaciens, a psychrotrophic bacteria frequently found in raw milk. To understand the physicochemical modifications of casein micelles induced by Ser2 and to confirm its implication in UHT milk destabilization, the enzyme was purified and added to microfiltered raw milk before UHT treatment. UHT milk destabilization was investigated during 90days of storage. A visual destabilization appeared after 8days of storage with the presence of sediment. Zeta potential increase and formation of aggregates were observed during the storage. Using tandem mass spectrometry, numerous released peptides from the four caseins were identified at the end of storage. Caseins were hydrolyzed in the preferential order β->αs1->κ->αs2. No specific peptidic hydrolysed bond was detected. The present study confirmed that the presence of the protease Ser2 in raw milk can be one of the main causes of UHT milk destabilization.