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Human milk is universally regarded as the gold standard to fulfill nutrition needs of infants. Lactoferrin (LF) is a major multiple bioactive glycoprotein in human milk but little is presented in infant formula. LF can resist digestion in the infant gastrointestinal tract and is absorbed into the bloodstream in an intact form to perform physiological functions. Evidence suggest that LF prevents pathogen infection, promotes immune system development, intestinal development, brain development and bone health, as well as ameliorates iron deficiency anemia. However, more clinical studies of LF need to be further elucidated to determine an appropriate dosage for application in infant formula. LF is sensitive to denaturation induced by processing of infant formula such as heat treatments and spay drying. Thus, further studies should be focus on maximizing the retention of LF activity in the infant formula process. This review summarizes the structural features of LF. Then the digestion, absorption and metabolism of LF in infants are discussed, followed by the function of LF for infants. Further, we summarize LF in infant formula and effects of processing of infant formula on bioactivities of LF, as well as future perspectives of LF research.

This review critically evaluates current in vitro gastrointestinal models for assessing infant formulas from a perspective focusing on a process along digestion, absorption and microbial fermentation. Despite their potential, none of the current in vitro gastrointestinal models fully considers the dynamics and continuous upstream‐downstream process of the human digestive tract. Considering the substantial differences between infants and adults, there is a pressing need for whole‐process gastrointestinal models tailored to infants. Developing such models is crucial for accurately assessing infant formula nutritional value and physiological function, enhancing the formulation of infant formulas to better meet the needs of infants. [ABSTRACT FROM AUTHOR]

• In vitro digestion of fermented milk with different casein-to-whey ratios was studied. • Less protein aggregates formed during gastric digestion at the casein-to-whey ratio of 2:1. • Gastric emptying rate varied insignificantly among the milk samples. • The protein digestibility was the highest at the casein-to-whey ratio of 2:1. • Release of overall and bioactive peptides was affected by casein-to whey ratios. The effects of casein-to-whey ratios (i.e., 4:1, 2:1, 1:1, 1:1.5) in fermented milk on gastric emptying, proteolysis and intestinal peptidome were investigated using an in vitro dynamic stomach-intestine system mimicking preschool children digestion. The gastric emptying rate varied insignificantly among the milk samples. After 120 min digestion, the protein digestibility was found in the range of 73.3–93.5 %, with the highest extent of proteolysis observed at a casein-to-whey ratio of 2:1 due to the fewest gastric protein aggregates and relatively abundant caseins. Intestinal peptides derived from caseins or whey proteins showed a positive correlation with their parent protein content. The most abundant bioactive whey peptides were found at casein-to-whey ratio of 1:1.5 after intestinal digestion. These findings demonstrated the importance of protein compositions in fermented milk on the gastrointestinal proteolysis and peptide release in vitro. This will be meaningful for future development of milk products that are more suitable for children. [ABSTRACT FROM AUTHOR]