Holder pasteurization impacts the proteolysis, lipolysis and disintegration of human milk under in vitro dynamic term newborn digestion

Abstract

International audienceWhen the mother’s own human milk is unavailable or limited, pasteurized human milk from milk banks is preferentially administered instead of infant formula, especially for vulnerable hospitalized neonates. Holder pasteurization (62.5 °C, 30 min) may alter human milk composition and structure, which may modulate its digestive behavior. An in vitro dynamic system was set up to simulate the gastrointestinal digestion of term newborns in order to compare the kinetics of lipolysis, proteolysis and structural disintegration of raw versus pasteurized human milk. Human milk from 5 donors was pooled. Half of the pool was either administrated raw (RHM) or pasteurized (PHM). Digestions were conducted at least in duplicate for RHM and PHM. Heat-induced protein aggregation was observed in PHM. During gastric digestion, β-casein was proteolyzed significantly faster for PHM than for RHM (p < 0.05), whereas lactoferrin tended to be proteolyzed slower (p = 0.07) for PHM. Pasteurization selectively affected the intestinal release of some amino acids. At any time of the gastrointestinal digestion, the lipolysis of PHM was significantly lower than that of RHM, but no impact was observed on the profile of released fatty acids. RHM presented a structural destabilization after 60 min of gastric digestion, while there was no large variation for PHM. In the intestinal phase, the evolution of the particle sizes was rather similar. Overall, Holder pasteurization impacted the proteolysis, lipolysis and disintegration of human milk. However, this impact was limited and the physiologic and metabolic consequences remain to be investigated

Impact of human milk pasteurization on the kinetics of peptide release during in vitro dynamic term newborn digestion

“…Here, PHM peptides were less intensely released during gastric digestion and resisted longer to intestinal hydrolysis. This could have had a quantitative impact on the overall β‐casein proteolysis, which would be in line with the previously observed reduced degree of gastric proteolysis for PHM β‐casein .…”

“…During gastrointestinal digestion, ␤-casein, the most abundant protein in human milk (2.7 g/L in mature milk [5]), generated almost 50% of the peptides, whilst ␣-lactalbumin, the second most abundant protein (2.5 g/L in mature milk [5]), represented Ͻ2% of the identified peptides, as reported previously [10,36]. This could reflect some proteolysis resistance of ␣-lactalbumin as observed by SDS-PAGE during gastric digestion of term human milk [8] or infant formula [37][38][39][40]. However, complete intestinal digestion was reported in pigs [37].…”

Towards infant formula biomimetic of human milk structure and digestive behaviour

“…de Oliveira et al (2015Oliveira et al ( , 2016 used an in vitro dynamic system (DIDGI ® ) to study the gastrointestinal digestion of pooled mature HM (n = 5) either raw (RHM) or pasteurized (PHM). The digestive behaviour of HM was characterized using either term and preterm infant digestive conditions.…”

“…Understanding the higher levels of organization of human MFGM or MFG has been delayed until the development of modern biophysical tools (among which confocal laser scanning microscopy). And yet, despite these developments and the obvious nutritional importance of HM, data on HM lipid structure remains limited (Simonin et al, 1984;Michalski et al, 2005b;Zou et al, 2012;de Oliveira et al, 2015de Oliveira et al, , 2016de Oliveira et al, , 2017. Many structural characteristics of HM MFG have been inferred from cow's MFG which paradoxically has been more studied.…”

“…Designing IF that mimic HM digestive behaviour supposes prior characterization of this behaviour. Recent work proposed by (de Oliveira et al, 2015(de Oliveira et al, , 2016 have described HM structural change during its passage through the upper gastrointestinal tract.…”