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

Effect of food enrichment based on diverse feeding regimes on the immunity of Nibea albiflora by biochemical and RNA-seq analysis of the spleen

Nibea albiflora is an economically valuable aquaculture species but suffers from various diseases caused by bacteria and parasites. It is necessary to investigate some novel methods to improve the immunity. In this study, three feeding regimes (A: commercial diet; B: 90 % commercial diet+10 % ice-fresh Exopalaemon carinicauda); C: 90 % commercial diet+5 % ice-fresh Exopalaemon carinicauda + 5 % live Perinereis nuntia, named Control group, Group 1 and Group 2 with similar nutrient and energy content were designed to construct the food enrichment model to investigate their effects on the immunity of this species. The study was focused on spleen tissue where biochemical and RNA-seq analysis were performed to reach our goals. The results showed that fish fed the enriched food showed higher immunity than the Control group fish. Food enrichment feeding also could enhance fish adaptive capacity which contributes to enhancing immunity. Compared to the Control group, the diet B feeding enhanced the fish immunity and adaptive capacity by up-regulating important genes like BAX, ITPR3, NOS1, NLRP3 and down-regulating the gene GOT1. Similarly for the diet C feeding, it improved not only fish immunity but also the neurotransmission activity associated with a good physiological condition by up regulating the genes ADCY5, CACNA1C, SMAD4, NOS1 and RXRB. The diet C feeding was the best in improving fish immunity. Above all, our study revealed the positive effects of such a food enrichment model on the fish and provided evidences and data which support the application of the feeding strategies in the healthy culturing of the fish.

Comparative proteomic analysis of donor human milk treated by high-pressure processing or Holder pasteurization on undigested proteins across dynamic simulated preterm infant digestion

High-pressure processing (HPP) of donor human milk (DM) minimally impacts the concentration and bioactivity of some important bioactive proteins including lactoferrin, and bile salt-stimulated lipase (BSSL) compared to Holder pasteurization (HoP), yet the impact of HPP and subsequent digestion on the full array of proteins detectable by proteomics remains unclear. We investigated how HPP impacts undigested proteins in DM post-processing and across digestion by proteomic analysis. Each pool of milk (n = 3) remained raw, or was treated by HPP (500 MPa, 10 min) or HoP (62.5 °C, 30 min), and underwent dynamic in vitro digestion simulating the preterm infant. In the meal, major proteins were minimally changed post-processing. HPP-treated milk proteins better resisted proximal digestion (except for immunoglobulins, jejunum 180 min) and the extent of undigested proteins after gastric digestion of major proteins in HPP-treated milk was more similar to raw (e.g., BSSL, lactoferrin, macrophage-receptor-1, CD14, complement-c3/c4, xanthine dehydrogenase) than HoP.

Peptidomic profile of human milk as influenced by fortification with different protein sources: An in vitro dynamic digestion simulation

Fortification of human milk (HM) is often necessary to meet the nutritional requirements of preterm infants. The present experiment aimed to establish whether the supplementation of HM with either an experimental donkey milk-derived fortifier containing whole donkey milk proteins, or with a commercial bovine milk-derived fortifier containing hydrolyzed bovine whey proteins, affects peptide release differently during digestion. The experiment was conducted using an in vitro dynamic system designed to simulate the preterm infant's digestion followed by digesta analysis by means of LC-MS-MS. The different fortifiers did not appear to influence the cumulative intensity of HM peptides. Fortification had a differential impact on the release of either donkey or bovine bioactive peptides. Donkey milk peptides showed antioxidant/ACE inhibitory activities, while bovine peptides showed opioid, dipeptil- and propyl endo- peptidase inhibitory and antimicrobial activity. A slight delay in peptide release from human lactoferrin and α-lactalbumin was observed when HM was supplemented with donkey milk-derived fortifier.

Human milk vs. Infant formula digestive fate: In vitro dynamic digestion and in vivo mini-piglet models lead to similar conclusions

Infant formula (IF), the only nutritionally adequate substitute for human milk (HM), still needs to be improved to be more biomimetic with HM, including in terms of digestive fate. The latter can be explored using different digestion models. The present study aimed to compare IF and HM digestion using in vivo (mini-piglet) and in vitro (dynamic system, DIDGI®) models. Fresh mature HM was collected and compared with a standard bovine IF. In vivo, 18 Yucatan mini-piglets (24-day-old) received HM or IF and were euthanized 30 min after the last meal. The entire digestive content was collected from the stomach to the colon. In vitro, the same meals were fed to an in vitro dynamic digestion model simulating the term infant at four weeks of age. Digesta were sampled regularly in the gastric and intestinal compartments. Structure (confocal microscopy and laser light scattering) and proteolysis (SDS-PAGE for residual intact proteins, OPA for hydrolysis degree, LC-MS/MS for peptides) were investigated along digestion. The digesta microstructure differed between HM and IF in a similar way between in vitro and in vivo digestion. In vitro gastric proteolysis of caseins and α-lactalbumin was significantly slower for HM than for IF, such as for the early intestinal proteolysis degree. In vitro bioaccessibility of free AAs explained only 30 % of the true ileal digestibility of AAs. Peptide mapping of caseins differed between HM and IF along their digestion. The relative peptide mapping data over six proteins from HM and IF were highly correlated between in vitro and in vivo digestion, particularly at 80 and 120 min of in vitro gastric digestion vs. in vivo stomach data and at 20 and 40 min of in vitro intestinal digestion vs. in vivo proximal jejunum data (r = 0.7-0.9, p < 0.0001, n = 1604). 40 to 50 % of the bioactive peptides identified in vivo were also found in vitro, with a good correlation of their abundances (r = 0.5, p < 0.0001, n = 61). Overall, in vitro and in vivo digestion were in good agreement, both indicating a different digestive fate for HM and IF.

Dynamic digestion of a high protein beverage based on amaranth: Structural changes and antihypertensive activity

An amaranth beverage (AB) was subjected to a simulated process of dynamic gastrointestinal digestion DIDGI®, a simple two-compartment in vitro dynamic gastrointestinal digestion system. The structural changes caused to the proteins during digestion and the digesta inhibitory capacity of the angiotensin converting enzyme (ACE) were investigated. In gastric compartment the degree of hydrolysis (DH) was 14.7 ± 1.5 % and in the intestinal compartment, proteins were digests in a greater extent (DH = 60.6 ± 8.4 %). Protein aggregation was detected during the gastric phase. The final digesta obtained both at the gastric and intestinal level, showed ACE inhibitory capacity (IC50 80 ± 10 and 140 ± 20 μg/mL, respectively). Purified fractions from these digesta showed even greater inhibitory capacity, being eluted 2 (E2) the most active fraction (IC50 60 ± 10 μg/mL). Twenty-six peptide sequences were identified. Six of them, with potential antihypertensive capacity, belong to A. hypochondriacus, 3 agglutinins and 3 encrypted sequences in the 11S globulin. Results obtained provide new and useful information on peptides released from the digestion of an amaranth based beverage and its ACE bioactivity.

Human Milk Protein-Derived Bioactive Peptides from In Vitro-Digested Colostrum Exert Antimicrobial Activities against Common Neonatal Pathogens

Human milk reduces risk for necrotizing enterocolitis in preterm infants. Necrotizing enterocolitis occurs in the ileocecal region where thousands of milk protein-derived peptides have been released from digestion. Digestion-released peptides may exert bioactivity, such as antimicrobial and immunomodulatory activities, in the gut. In this study, we applied mass spectrometry-based peptidomics to characterize peptides present in colostrum before and after in vitro digestion. Sequence-based computational modeling was applied to predict peptides with antimicrobial activity. We identified more peptides in undigested samples, yet the abundances were much higher in the digested samples. Heatmapping demonstrated highly different peptide profiles between undigested and digested samples. Four peptides (αS1-casein [157-163], αS1-casein [157-165], β-casein [153-159] and plasminogen [591-597]) were selected, synthesized and tested against common pathogenic bacteria associated with necrotizing enterocolitis. All four exhibited bacteriostatic, though not bactericidal, activities against Klebsiella aerogenes, Citrobacter freundii and Serratia marcescens, but not Escherichia coli.

Bovine milk β-casein: Structure, properties, isolation, and targeted application of isolated products

β-Casein, an important protein found in bovine milk, has significant potential for application in the food, pharmaceutical, and other related industries. This review first introduces the composition, structure, and functional properties of β-casein. It then reviews the techniques for isolating β-casein. Chemical and enzymatic isolation methods result in inactivity of β-casein and other components in the milk, and it is difficult to control the production conditions, limiting the utilization range of products. Physical technology not only achieves high product purity and activity but also effectively preserves the biological activity of the components. The isolated β-casein needs to be utilized effectively and efficiently for various purity products in order to achieve optimal targeted application. Bovine β-casein, which has a purity higher than or close to that of breast β-casein, can be used in infant formulas. This is achieved by modifying its structure through dephosphorylation, resulting in a formula that closely mimics the composition of breast milk. Bovine β-casein, which is lower in purity than breast β-casein, can be maximized for the preparation of functional peptides and for use as natural carriers. The remaining byproducts can be utilized as food ingredients, emulsifiers, and carriers for encapsulating and delivering active substances. Thus, realizing the intensive processing and utilization of bovine β-casein isolation. This review can promote the industrial production process of β-casein, which is beneficial for the sustainable development of β-casein as a food and material. It also provides valuable insights for the development of other active substances in milk.

The impact of heating and drying on protease activities of ruminant milk before and after in vitro infant digestion

This study investigated the effect of heating (63°C/30 min or 75°C/15 s) and drying (spray-drying or freeze-drying) on plasmin, cathepsin D, and elastase activities in bovine, ovine, and caprine milk, compared to non-dried raw milk counterparts. Protease activities and protein hydrolysis were assessed before and after in vitro infant digestion with or without gastric and pancreatic enzymes. At 75°C/15 s, plasmin activity in caprine and ovine milk decreased (69-75%, p<0.05), while cathepsin D activity in spray-dried bovine milk heated increased (2.8-fold, p<0.05). Plasmin and cathepsin D activities increased (<1.2-fold, p<0.05) after in vitro digestion with pancreatin, regardless of milk species. Endogenous milk enzymes hydrolyzed more proteins than gastric enzymes during gastric digestion and contributed to small intestinal digestion. In summary, milk proteases remained active after processing with effects dependent on the species of milk, and they contributed to in vitro protein hydrolysis in the stomach and small intestine.

Proteomics and Peptidomics As a Tool to Compare the Proteins and Endogenous Peptides in Human, Cow, and Donkey Milk

Cow's milk is the most widely used ingredient in infant formulas. However, its specific protein composition can cause allergic reactions. Finding alternatives to replace cow's milk and fill the nutritional gap with human milk is essential for the health of infants. Proteomic and peptidomic techniques have supported the elucidation of milk's nutritional ingredients. Recently, omics approaches have attracted increasing interest in the investigation of milk because of their high throughput, precision, sensitivity, and reproducibility. This review offers a significant overview of recent developments in proteomics and peptidomics used to study the differences in human, cow, and donkey milk. All three types of milks were identified to have critical biological functions in human health, particularly in infants. Donkey milk proteins were closer in composition to human milk, were less likely to cause allergic reactions, and may be developed as novel raw materials for formula milk powders.

Characterization and biological function analysis of endogenous peptides derived from donkey colostrum proteins

Donkey colostrum, due to its abundance of active ingredients, including lysozyme, proteins, and peptides, is essential for the growth and immune defence of newborns. However, research on endogenous peptides in donkey colostrum is inadequate. This study analysed the profiles of endogenous peptides, their potential bioactivity, and the enzymes that generated these peptides using two different strategies. A total of 6202 endogenous peptides were characterised through a database search, while an additional 2997 peptides were identified de novo. Among the 1142 proteins identified, trypsin and plasmin demonstrated the highest bioactivities. Furthermore, a bioinformatics-based screening identified antioxidant peptides, angiotensin I-converting enzyme inhibitory peptides, and dipeptidyl peptidase IV inhibitory peptides as the three most active peptides. Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were conducted. These findings enhance our knowledge of endogenous peptides in donkey colostrum and provide crucial information regarding these peptides as nutritional factors for the future development of functional foods derived from donkey sources.

A longitudinal study of fatty acid profiles, macronutrient levels, and plasmin activity in human milk

Introduction

Human milk provides nutrients essential for infant growth and health, levels of which are dynamic during lactation.

Methods

In this study, changes in macronutrients, fatty acids, and plasmin activities over the first six months of lactation in term milk were studied.

Results

There was a significant influence of lactation stage on levels of protein and plasmin activities, but not on levels of fat and carbohydrate in term milk. Concerning fatty acids in term milk, levels of caproic acid and α-linolenic acid increased significantly (p < 0.05), whereas those of arachidonic acid and docosahexaenoic acid decreased, in the six months after birth. Significant impacts of maternal pre-pregnancy BMI and infant gender on fatty acid profiles were also found. Multivariate statistical analysis showed that protein level, plasmin activity, and several fatty acids (α-linolenic acid, lignoceric acid, and docasadienoic acid) contributed strongly to discrimination of milk from different lactational stages.

Discussion

The study demonstrates that not all but some fatty acids were influenced by lactation, whereas protein and protease levels showed clear decreasing trends during lactation, which may help in understanding the nutritional requirements of infants.

Ecologies, synergies, and biological systems shaping human milk composition-a report from "Breastmilk Ecology: Genesis of Infant Nutrition (BEGIN)" Working Group 2

Human milk is universally recognized as the preferred food for infants during the first 6 mo of life because it provides not only essential and conditionally essential nutrients in necessary amounts but also other biologically active components that are instrumental in protecting, communicating important information to support, and promoting optimal development and growth in infants. Despite decades of research, however, the multifaceted impacts of human milk consumption on infant health are far from understood on a biological or physiological basis. Reasons for this lack of comprehensive knowledge of human milk functions are numerous, including the fact that milk components tend to be studied in isolation, although there is reason to believe that they interact. In addition, milk composition can vary greatly within an individual as well as within and among populations. The objective of this working group within the Breastmilk Ecology: Genesis of Infant Nutrition (BEGIN) Project was to provide an overview of human milk composition, factors impacting its variation, and how its components may function to coordinately nourish, protect, and communicate complex information to the recipient infant. Moreover, we discuss the ways whereby milk components might interact such that the benefits of an intact milk matrix are greater than the sum of its parts. We then apply several examples to illustrate how milk is better thought of as a biological system rather than a more simplistic "mixture" of independent components to synergistically support optimal infant health.

[Variation in the level of the biocomponents immunoglobulin A and lactoferrin in human milk after Holder pasteurization]

BACKGROUND

breast milk is the ideal food for newborns and infants, but there are factors that can prevent the practice of breastfeeding. Human milk banks (BLH) are a strategy to increase breastfeeding coverage; the donated milk is subjected to Holder pasteurization to guarantee its innocuousness, undergoing large changes in temperature and a decrease in the concentrations of biocomponents such as Immunoglobulin A (IgA) and lactoferrin (LF). This article describes the results of recent studies on the impact of Holder pasteurization on IgA and LF in human milk.

MATERIAL AND METHODS

a search for research articles related to the topic of interest was carried out in various databases and in accordance with inclusion criteria that considered the type of study, date of publication and quality of the journal.

RESULTS

the impact of Holder pasteurization on IgA and LF concentrations is not clear, given that the literature reports a variety of protocols and different results; however, the percentage reductions of both biocomponents are significant and consistent in the studies reviewed, suggesting the importance of establishing a standard protocol for their quantification.

CONCLUSIONS

Holder pasteurization guarantees the microbiological quality of the milk distributed in HMB, but affects the amount of beneficial biocomponents for the final recipient. Government entities that regulate HMBs should evaluate the possibility of using other techniques that reduce the impact on biocomponents while preserving the microbiological quality of the product.

Development of a human milk protein concentrate from donor milk: Impact of the pasteurization method on static in vitro digestion in a preterm newborn model

The impact of high temperature short time (HTST, 72 °C, 15 s), Holder pasteurization- (63 °C, 30 min) and high hydrostatic pressure (HHP, 600 MPa-10 min) was evaluated on the digestibility of human milk protein concentrate (HMPC) by using a static in vitro gastrointestinal digestion system. The results showed that the processing steps used to produce the HMPC induced a decrease in readily available nitrogen (non-protein nitrogen and peptides). Overall, digestibility was similar between pasteurized and raw HMPC (degree of hydrolysis ranged from 26 to 34 %). Lactoferrin was more susceptible to gastric and intestinal digestion after thermal pasteurization. Additionally, the resistance of β-casein to digestion increased after HHP and Holder pasteurization due to aggregation and changes in protein structure. During intestinal digestion, Holder pasteurization induced a higher release of arginine, phenylalanine and tyrosine from HMPC compared to raw and HHP-treated HMPC. Overall, protein structural changes induced by human milk (HM) processing (freeze-thawing and filtration) and pasteurization treatments affected HMPC proteolysis during in vitro digestion. However, protein digestion behaviors were quite similar for raw and HHP-treated HMPC compared to the thermal-treated HMPC, with no effect on lactoferrin digestion. Consequently, pasteurization of HMPC by HHP represents an interesting non-thermal process that preserves the HM bioactive proteins during digestion.

Donor human milk processing and its impact on infant digestion: A systematic scoping review of in vitro and in vivo studies

When there is an inadequate supply of mother's milk, pasteurized donor human milk is preferred over formula to supplement feeds for preterm infants. Although providing donor milk helps to improve feeding tolerance and reduce necrotizing enterocolitis, changes to its composition and reductions in bioactivity during processing, are thought to contribute to the slower growth often exhibited by these infants. To improve the clinical outcomes of recipient infants by maximizing the quality of donor milk, research is currently investigating strategies to optimize all aspects of processing, including pooling, pasteurization, and freezing; however, reviews of this literature typically only summarize the impact of a processing technique on composition or bioactivity. Reviews of published research investigating the impact of donor milk processing on infant digestion/absorption are lacking and thus, was the objective for this systematic scoping review, Open Science Framework (https://doi.org/10.17605/OSF.IO/PJTMW). Databases were searched for primary research studies evaluating donor milk processing for pathogen inactivation or other rationale and subsequent effect on infant digestion/absorption. Non-human milk studies or those assessing other outcomes were excluded. Overall, 24 articles from 12,985 records screened were included. Most studied thermal methods to inactivate pathogens, predominantly Holder pasteurization (HoP) (62.5°C, 30 min) and high-temperature short-time. Heating consistently decreased lipolysis and increased proteolysis of lactoferrin and caseins; however, protein hydrolysis was unaffected from in vitro studies. The abundance and diversity of released peptides remain unclear and should be further explored. Greater investigation into less-harsh methods for pasteurization, such as high-pressure processing, is warranted. Only 1 study assessed the impact of this technique and found minimal impact on digestion outcomes compared with HoP. Fat homogenization appeared to positively impact fat digestion (n = 3 studies), and only 1 eligible study investigated freeze-thawing. Identified knowledge gaps regarding optimal methods of processing should be further explored to improve the quality and nutrition of donor milk.

Preterm birth and human milk proteome: are we ready for individualized fortification?

PURPOSE OF REVIEW

Preterm birth is one of the most pressing clinical problems in obstetrics and neonatology worldwide. One of the most sophisticated components of human milk is the proteome and a better understanding of it can lead to precision guides for feeding preterm infants. In this review, we will examine recent research focused on the human milk proteome and individualized protein fortification of human milk.

RECENT FINDINGS

In both preterm and term birth, the protein content in mother's own milk dropped rapidly in the early postnatal period. Preterm milk had a higher protein content and contained different protein and endogenous peptide compositions compared with term milk. The peptides in gastrointestinal fluids of preterm infants still need further investigation. Individualized fortification is more superior to standard fortification, but it only focuses on the total protein amount. There is no data concerning the composition and posttranslational modifications of proteins and endogenous peptides with fortification and their longterm effects.

SUMMARY

Comprehensive identification and characterization of the human milk proteome have led to the targeted breast milk fortification theory of preterm infant feeding and has also been enriched by clinical trials. However, to achieve fortification of key proteins and/or endogenous peptides, as standard clinical practice, requires additional studies. Future research should explore the long-term effect of protein fortification and pay more attention to quality rather than quantity in relation to infant body composition and growth outcomes.

In Vitro Anti-Inflammatory Activity of Peptides Obtained by Tryptic Shaving of Surface Proteins of Streptococcus thermophilus LMD-9

Streptococcus thermophilus, a lactic acid bacterium widely used in the dairy industry, is consumed regularly by a significant proportion of the population. Some strains show in vitro anti-inflammatory activity which is not fully understood. We hypothesized that peptides released from the surface proteins of this bacterium during digestion could be implied in this activity. Consequently, we prepared a peptide hydrolysate by shaving and hydrolysis of surface proteins using trypsin, and the origin of peptides was checked by liquid chromatography–tandem mass spectrometry (LC-MS/MS) analysis. Most of the identified peptides originated from bacterial cell surface proteins. The anti-inflammatory activity of peptide hydrolysate was investigated under inflammatory conditions in two cell models. Peptide hydrolysate significantly decreased secretion of pro-inflammatory cytokine IL-8 in lipopolysaccharide (LPS)-stimulated human colon epithelial HT-29 cells. It also reduced the production of pro-inflammatory cytokines IL-8, IL-1β and the protein expression levels of Pro-IL-1β and COX-2 in LPS-stimulated THP-1 macrophages. The results showed that peptides released from bacterial surface proteins by a pancreatic protease could therefore participate in an anti-inflammatory activity of S. thermophilus LMD-9 and could prevent low-grade inflammation.

Simulated dynamic digestion reveals different peptide releases from human milk processed by means of holder or high temperature-short time pasteurization

High Temperature-Short Time (HTST) pasteurization was proposed as an alternative to Holder pasteurization (HOP) to increase the retention of specific human milk (HM) bioactive proteins. The present study explored whether HTST and HOP differently affect peptide release during simulated preterm infant gastrointestinal digestion. Raw (RHM), HOP- and HTST- pasteurized HM were digested using an in vitro dynamic system, and the identified peptides were analyzed by mass spectrometry and multivariate statistics. Before digestion, 158 peptides were identified in either RHM, HTST- or HOP- HM, mostly (84.4%) originating from β-casein (CASB). During gastric digestion, HOP-HM presented a greater number and more abundant specific CASB peptides. A delayed release of peptides was observed in RHM during the intestinal phase, with respect to both pasteurized HM. Although limited to gastric digestion, the HM peptidomic profile differed according to the pasteurization type, and the pattern of the HTST peptides showed a greater similarity with RHM.

Positive Interactions Between Lactic Acid Bacteria Could Be Mediated by Peptides Containing Branched-Chain Amino Acids

Lactic acid bacteria (LAB) are responsible for the sanitary, organoleptic, and health properties of most fermented products. Positive interactions between pairs of LAB strains, based on nitrogen dependencies, were previously demonstrated. In a chemically defined medium, using milk and lupin proteins as sole nitrogen source, two proteolytic strains were able to sustain the growth of non-proteolytic strains, but one did not. The objective of the present study was, thus, to determine which specific peptides were implicated in the positive interactions observed. Peptides produced and involved in the bacterial interactions were quantified using tandem mass spectrometry (LC-MS/MS). About 2,000 different oligopeptides ranging from 6 to more than 50 amino acids in length were identified during the time-course of the experiment. We performed a clustering approach to decipher the differences in peptide production during fermentation by the three proteolytic strains tested. We also performed sequence alignments on parental proteins and identified the cleavage site profiles of the three bacterial strains. Then, we characterized the peptides that were used by the non-proteolytic strains in monocultures. Hydrophobic and branched-chain amino acids within peptides were identified as essential in the interactions. Ultimately, better understanding how LAB can positively interact could be useful in multiple food-related fields, e.g., production of fermented food products with enhanced functional properties, or fermentation of new food matrices.

Effect of pasteurization on melatonin concentration in human breast milk

Introduction

Women who have problems with lactation can use human milk banks. Mainly this human milk is provided to premature babies and sick newborns. Human milk is the most suitable food for newborns and infants, recommended by WHO (World Health Organization). Human milk has anti-inflammatory, anti-infective, and anti-allergic properties, and also works for immunomodulation. Melatonin has a special, underestimated importance in the composition of breast milk. It is a hormone that has many body functions and, for several decades, its antioxidant potential has been increasingly talked about.

The aim of the study was to examine the effect of Holder pasteurization on melatonin concentration in human milk.

Materials and Methods

18 samples of human milk from donors from the human milk bank were used for the analysis. Melatonin concentration before and after pasteurization was determined by ELISA. In addition, the nutritional content composition of milk was analyzed using MIRIS Human Milk Analyzer and correlations examined.

Results

Melatonin concentration in human milk before pasteurization was 0.65–26.24 pg/mL (Me=9.58, IQR=12.72), while after pasteurization 0.80–29.58 pg/mL (Me=9.98, IQR=11.26). There was a positive correlation between melatonin concentration before and after pasteurization (r=0.797, p<0.001).

Conclusions

The Holder pasteurization process does not affect the concentration of melatonin in milk samples, which may be a recommendation for human milk banks.

Inoculation of mother's own milk could personalize pasteurized donor human milk used for feeding preterm infants

BACKGROUND

Human milk is a vehicle for bioactive compounds and beneficial bacteria which promote the establishment of a healthy gut microbiome of newborns, especially of preterm infants. Pasteurized donor human milk (PDHM) is the second-best option when preterm mother's own milk is unavailable. Since pasteurization affect the microbiological quality of donor milk, PDHM was inoculated with different preterm milk samples and then incubated, in order to evaluate the effect in terms of bacterial growth, human milk microbiome and proteolytic phenomena.

METHODS

In an in-vitro study PDHM was inoculated at 10% v/v using ten preterm milk samples. Microbiological, metataxonomic and peptidomic analyses, on preterm milk samples at the baseline (T0), on PDHM and on inoculated milk (IM) samples at T0, after 2 h (T1) and 4 h (T2) of incubation at 37 °C, were conducted.

RESULTS

IM samples at T2 showed a Total Bacterial Count not significantly different (p > 0.01) compared to preterm milk samples. At T2 lactic acid bacteria level was restored in all IM. After inoculation, metataxonomic analysis in IM samples showed that Proteobacteria remained the predominant phylum while Firmicutes moved from 3% at T1 to 9.4% at T2. Peptidomic profile of IM resembled that of PDHM, incubated for the same time, in terms of number and type of peptides.

CONCLUSION

The study demonstrated that inoculation of PDHM with mother's own milk could restore bacterial growth and personalize human milk microbiome in PDHM. This effect could be beneficial because of the presence of maternal probiotic bacteria which make PDHM more similar to mother's own milk.

Understanding protein digestion in infants and the elderly: Current in vitro digestion models

The last decades have witnessed a surge of interest in the fate of dietary proteins during gastrointestinal (GI) digestion. Although several in vitro digestion models are available as alternatives to clinical experiments, most of them focus on the digestive conditions of healthy young adults. This study investigates the static/dynamic models used to simulate digestion in infants and the elderly and considers the related in vivo conditions. The in vitro digestive protocols targeting these two groups are summarized, and the challenges associated with the further development of in vitro digestion models are discussed. Static models rely on several factors (e.g., enzyme concentration, pH, reaction time, and rotation speed) to differentiate digestive conditions depending on age. Dynamic models can more accurately simulate the complex digestion process and allow the inclusion of further parameters (sequential secretion of digestive fluids, gradual changes in pH, peristaltic mixing, GI emptying, and the inoculation of luminal microbiota). In the case of infants, age or growth stage clarification and the differentiation of digestive protocols between full-term and preterm infants are required, whereas protocols dealing with various health statuses are required in the case of the elderly, as this group is prone to oral cavity and GI function deterioration.

Monitoring Human Milk β-Casein Phosphorylation and O-Glycosylation Over Lactation Reveals Distinct Differences between the Proteome and Endogenous Peptidome

Human milk is a vital biofluid containing a myriad of molecular components to ensure an infant's best start at a healthy life. One key component of human milk is β-casein, a protein which is not only a structural constituent of casein micelles but also a source of bioactive, often antimicrobial, peptides contributing to milk's endogenous peptidome. Importantly, post-translational modifications (PTMs) like phosphorylation and glycosylation typically affect the function of proteins and peptides; however, here our understanding of β-casein is critically limited. To uncover the scope of proteoforms and endogenous peptidoforms we utilized mass spectrometry (LC-MS/MS) to achieve in-depth longitudinal profiling of β-casein from human milk, studying two donors across 16 weeks of lactation. We not only observed changes in β-casein's known protein and endogenous peptide phosphorylation, but also in previously unexplored O-glycosylation. This newly discovered PTM of β-casein may be important as it resides on known β-casein-derived antimicrobial peptide sequences.

Human milk proteome: what's new?

PURPOSE OF REVIEW

The proteome is one of the most complicated and multifunctional components in human milk. Recently, numerous novel characteristics of the human milk proteome have been discovered, which are described and critically examined in this review.

RECENT FINDINGS

Recent human milk proteomics studies have focused on how external factors like geography and environment, or maternal and infant's factors affect the milk proteins, endogenous peptides, their posttransitional modifications (PTMs) and infant utilization. Most of these studies have shown that major protein and endogenous peptide profiles are similar for healthy women and infants. The human milk proteome has been expanded by providing novel insights into PTMs like glycosylation and phosphorylation, and how the proteins and peptides are digested and utilized by the infant. All human milk proteomics studies are subject to conditions in which the samples were collected, handled and stored.

SUMMARY

Significant technological advancements in mass spectrometry have considerably enabled a deeper and more comprehensive identification and characterization of the expanded human milk proteome. However, data concerning human milk from mothers with infections or illnesses and mothers nursing more vulnerable infants are still limited and the roles of the components of the human milk proteome have not yet been sufficiently elucidated.

Antimicrobial Potential of Food Lactic Acid Bacteria: Bioactive Peptide Decrypting from Caseins and Bacteriocin Production

Lactic acid bacteria (LAB) potential in the food industry and in the biotechnological sector is a well-established interest. LAB potential in counteracting especially food-borne infections has received growing attention, but despite being a road full of promises is yet poorly explored. Furthermore, the ability of LAB to produce antimicrobial compounds, both by ribosomal synthesis and by decrypting them from proteins, is of high value when considering the growing impact of multidrug resistant strains. The antimicrobial potential of 14 food-derived lactic acid bacteria strains has been investigated in this study. Among them, four strains were able to counteract Listeria monocytogenes growth: Lactococcus lactis SN12 and L. lactis SN17 by high lactic acid production, whereas L. lactis 41FLL3 and Lactobacillus sakei I151 by Nisin Z and Sakacin P production, respectively. Strains Lactococcus lactis MG1363, Lactobacillus rhamnosus 17D10 and Lactobacillus helveticus 4D5 were tested and selected for their potential attitude to hydrolyze caseins. All the strains were able to release bioactive peptides with already known antimicrobial, antihypertensive and opioid activities. These features render these strains or their bioactive molecules suitable for use in food as biocontrol agents, or as nutraceutical supplements to treat mild disorders such as moderate hypertension and children insomnia. These results highlight once again that LAB potential in ensuring food safety, food nutraceutical value and ultimately in favoring human health is still underexplored and underexploited.

Current Evidence on the Bioavailability of Food Bioactive Peptides

Food protein-derived bioactive peptides are recognized as valuable ingredients of functional foods and/or nutraceuticals to promote health and reduce the risk of chronic diseases. However, although peptides have been demonstrated to exert multiple benefits by biochemical assays, cell culture, and animal models, the ability to translate the new findings into practical or commercial uses remains delayed. This fact is mainly due to the lack of correlation of in vitro findings with in vivo functions of peptides because of their low bioavailability. Once ingested, peptides need to resist the action of digestive enzymes during their transit through the gastrointestinal tract and cross the intestinal epithelial barrier to reach the target organs in an intact and active form to exert their health-promoting properties. Thus, for a better understanding of the in vivo physiological effects of food bioactive peptides, extensive research studies on their gastrointestinal stability and transport are needed. This review summarizes the most current evidence on those factors affecting the digestive and absorptive processes of food bioactive peptides, the recently designed models mimicking the gastrointestinal environment, as well as the novel strategies developed and currently applied to enhance the absorption and bioavailability of peptides.

Differences in human milk peptide release along the gastrointestinal tract between preterm and term infants

BACKGROUND & AIMS

Preterm infants are born with a gastrointestinal tract insufficiently developed to digesting large quantities of human milk proteins. Peptides released from the digestion of human milk proteins have been identified with bioactivities that may be beneficial to the developing infant. However, it is unknown how prematurity affects total and bioactive peptide release along the gastrointestinal tract. The aim of this study was to compare milk peptide release from milk to stomach to stool between preterm and term infants.

METHODS

Milk, gastric, and stool samples were collected from preterm infants as early collection (days 8 and 9 of life) and late collection (days 21 and 22 of life), and from term infants as early collection. Milk peptides were extracted from the samples and identified using Orbitrap mass spectrometry. Peptide abundance and count were compared across digestion and between the three infant groups at each stage of digestion.

RESULTS

Total milk peptide count and abundance increased from milk to stomach then decreased in stool. Total peptide release was similar among the three infant groups for milk and stool samples. In the stomach, preterm early collection had significantly higher peptide abundance and count than the other two groups. Patterns for peptide release from individual milk proteins were distinct from total peptide release both across digestion and among the infant groups. When analyzing single peptides, term early collection gastric samples had significantly higher peptide abundance than preterm early collection for a known antimicrobial peptide, QELLLNPTHQIYPVTQPLAPVHNPISV.

CONCLUSIONS

Preterm and term infants digest milk proteins differently along their gastrointestinal tracts. While preterm infants released more total peptides in the stomach, term infants released specific bioactive peptides at higher abundance. We identified a region at the C-terminus of β-casein that is conserved from milk through stool and from which are released known and potential antimicrobial peptides.

Influence of Pasteurization and Storage on Dynamic In Vitro Gastric Digestion of Milk Proteins: Quantitative Insights Based on Peptidomics

It is important to evaluate the nutritional quality of milk during the shelf-life, especially during home storage, from a consumer viewpoint. In this study, we investigated the impact of pasteurization (85 °C/15 s) and subsequent storage (at 4 °C for 7 days) on the coagulation behavior of milk and protein digestibility in a dynamic in vitro gastric digestion test. A high level of hydration in curd formed in pasteurized milk upon 7-day cold storage compared to raw and pasteurized milk, indicating fast pepsin diffusion in the interior of curds, increasing the hydrolysis rate. The digesta collected at various time points throughout the gastric digestion were studied using o-phthaldialdehyde (OPA), sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), liquid chromatography tandem mass spectrometry (LC-MS/MS), and amino acid analysis. These results showed that milk proteins were hydrolyzed quickly upon a long period of cold storage. Additionally, qualitative and quantitative results obtained using LC-MS/MS exhibited significant differences between samples, especially in pasteurized milk upon cold storage. Processing and storage played a decisive role in bioactive peptide generation. Such knowledge could provide insights into and directions for the storage of pasteurized milk for further clinical studies on protein bioavailability and the generation of bioactive peptides for desired health outcomes.

Modification of protein structures by altering the whey protein profile and heat treatment affects in vitro static digestion of model infant milk formulas

Heat treatments induce changes in the protein structure in infant milk formulas (IMFs). The present study aims to investigate whether these structural modifications affect protein digestion. Model IMFs (1.3% proteins), with a bovine or a human whey protein profile, were unheated or heated at 67.5 °C or 80 °C to reach 65% of denaturation, resulting in six protein structures. IMFs were submitted to in vitro static gastrointestinal digestion simulating infant conditions. During digestion, laser light scattering was performed to analyze IMF destabilization and SDS-PAGE, OPA assay and cation exchange chromatography were used to monitor proteolysis. Results showed that, during gastric digestion, α-lactalbumin and β-lactoglobulin were resistant to hydrolysis in a similar manner for all protein structures within IMFs (p > 0.05), while the heat-induced denaturation of lactoferrin significantly increased its susceptibility to hydrolysis. Casein hydrolysis was enhanced when the native casein micelle structure was modified, i.e. partially disintegrated in the presence of lactoferrin or covered by heat-denatured whey proteins. The IMF destabilization at the end of the gastric digestion varied with protein structures, with larger particle size for IMF containing native casein micelles. During intestinal digestion, the kinetics of protein hydrolysis varied with the IMF protein structures, particularly for IMFs containing denatured lactoferrin, exhibiting higher proteolysis degree (67.5 °C and 80 °C vs. unheated) and essential amino acid bioaccessibility (67.5 °C vs. unheated). Overall, the protein structures, generated by modulating the whey protein profile and the heating conditions, impacted the IMF destabilization during the gastric phase and the proteolysis during the entire simulated infant digestion.

Effect of protein aggregation in wheat-legume mixed pasta diets on their in vitro digestion kinetics in comparison to "rapid" and "slow" animal proteins

The aim of this work was to evaluate the impact of incorporating different legume flours (faba bean, lentil or split pea flours) on the pasta protein network and its repercussion on in vitro protein digestibility, in comparison with reference dairy proteins. Kinetics and yields of protein hydrolysis in legume enriched pasta and, for the first time, the peptidomes generated by the pasta at the end of the in vitro gastric and intestinal phases of digestion are presented. Three isoproteic (21%) legume enriched pasta with balanced essential amino acids, were made from wheat semolina and 62% to 79% of legume flours (faba bean or F-pasta; lentil or L-pasta and split pea or P-pasta). Pasta were prepared following the conventional pastification steps (hydration, mixing, extrusion, drying, cooking). Amino acid composition and protein network structure of the pasta were determined along with their culinary and rheological properties and residual trypsin inhibitor activity (3-5% of the activity initially present in raw legume flour). F- and L-pasta had contrasted firmness and proportion of covalently linked proteins. F-pasta had a generally weaker protein network and matrix structure, however far from the weakly linked soluble milk proteins (SMP) and casein proteins, which in addition contained no antitrypsin inhibitors and more theoretical cleavage sites for digestive enzymes. The differences in protein network reticulation between the different pasta and between pasta and dairy proteins were in agreement in each kinetic phase with the yield of the in vitro protein hydrolysis, which reached 84% for SMP, and 66% for casein at the end of intestinal phase, versus 50% for L- and P-pasta and 58% for F-pasta. The peptidome of legume enriched pasta is described for the first time and compared with the peptidome of dairy proteins for each phase of digestion. The gastric and intestinal phases were important stages of peptide differentiation between legumes and wheat. However, peptidome analysis revealed no difference in wheat-derived peptides in the three pasta diets regardless of the digestion phase, indicating that there was a low covalent interaction between wheat gluten and legume proteins.

Bioactive peptides derived from human milk proteins: an update

PURPOSE OF REVIEW

Human milk contains a variety of bioactive proteins, and some of the bioactivities are exerted only after proteins are digested in the gastrointestinal tract. This review aims to overview recent studies on bioactive peptides in human milk and gastric digesta of breast-fed infants.

RECENT FINDINGS

Milk protein-derived peptides are endogenously present in human milk, and some of them have been reported to be bioactive peptides, such as a homologue of caseinophosphopeptide, an antimicrobial peptide, and an immunomodulatory peptide. A larger number of peptides are identified in gastric aspirates from breast-fed infants, and bioactive peptides such as angiotensin I-converting enzyme-inhibitory peptides, an antioxidative peptide, opioid agonist peptides are only found in the digesta of human milk but not in human milk per se. Casein is the greatest source of released bioactive peptides.

SUMMARY

Technological advances have considerably increased our capability to identify and characterize peptides derived from human milk proteins. However, their physiological significance and the roles of these bioactive peptides in growth and development of breast-fed infants have not yet been sufficiently elucidated, and further in-vivo experiments and clinical trials are warranted.