A comprehensive review on in vitro digestion of infant formula

Dairy Foods: A Matrix for Human Health and Precision Nutrition-Effect of processing infant milk formula on protein digestion and gut barrier health (in vitro and preclinical)

The infant gut is immature and permeable with high gastric pH, low protease activities, and underdeveloped intestinal architecture. Protein digestion in the upper gastrointestinal tract of infants is slow and incomplete. During manufacture, infant milk formula (IMF) is typically heat-treated so it is safe for human consumption. This heat treatment causes denaturation and aggregation of milk proteins, and formation of undesirable Maillard reaction products. The aim of this review is to critically summarize the in vitro and preclinical data available on the effect of IMF thermal processing on protein digestion and gut barrier physiology in the immature infant gut. Recent research efforts have focused on reducing thermal loads during IMF manufacturing by sourcing ingredients with low thermal loads, by reducing temperatures during IMF processing itself, and by seeking alternative processing technologies. This review also aims to evaluate whether these thermal reductions have a knock-on effect on protein digestion and gut barrier health in the infant. The ultimate aim is to create a safe next-generation IMF product that more closely mimics human breast milk in its protein digestion kinetics and its ability to promote gut barrier maturity in the infant.

Protein Digestibility and Anti-inflammatory Activity of Processed Whey Protein Ingredients for Infant Formula

Conventional whey protein concentrate (WPC) and gently processed skim-milk-derived WPC (SPC) undergo heat processing to ensure microbial safety before use in infant formula products. Heat treatment and storage induce protein structural changes, which may modulate digestibility and bioactivity. The objective of the study was to evaluate the effect of heat treatment and storage on the SPC ingredient by subjecting it to heat treatment (80 °C, 30 s) with or without an additional six-week storage at 37 °C (resulting in HT-SPC and HTS-SPC, respectively) and to compare these effects with a reference WPC ingredient. Reducible aggregates were present in HT-SPC, HTS-SPC, and WPC but not in the control SPC ingredient. As assessed in vitro, infant gastric digestion conditions had a limited hydrolytic effect on whey proteins, while significant protein hydrolysis occurred under infant intestinal conditions. WPC was more digestible than SPC, and additional heat treatment of SPC increased the protein digestibility. The digested protein ingredients exhibited similar anti-inflammatory activity (e.g., inhibition of the NFκB pathway in THP-1 macrophages in vitro). In conclusion, the SPC ingredient was less digestible, which was improved by heat treatment but with similar bioactivity as a conventional WPC ingredient.

Comparative Study of Human Milk and Infant Formulas at Different Stages Based on Dynamic In Vitro Infant Gastrointestinal Digestion: The Effect of Polar Lipids on Lutein Digestion

The efficiency of the absorption and digestion of lutein in infant formulas (IFs) is remarkably lower than that in human milk. This work compared the simulated in vitro dynamic digestive characteristics of lutein in three stages of human milk and six IFs, with a special emphasis on how polar lipids affect lutein digestion. Compared with colostrum (CM), IF2 had a significantly higher lutein loss rate but significantly lower micellarization and bioaccessibility rates. In CM, the morphology of milk fat globules (MFGs) remained visible after digestion; the phospholipid globular membrane structure can be observed after 180 min of intestinal digestion, and MFGs remained in a spherical form in micelles. Lipidomic analysis precisely quantified 18 significantly different lipids, including cholesterol, phosphatidylcholine, phosphatidylserine, phosphatidylinositol, phosphatidic acid, and phosphatidylglycerol, between CM and IF2 micelles, suggesting that these lipids may influence the micellarization of lutein. In summary, polar lipids play an important role in the protection of lutein and the facilitation of lutein micellarization. These findings also provide a certain reference for the adjustment of IF formulations.

Oxidative Lipidomics to Unravel the Glycerol Core Aldehydes of Three Typical Unsaturated Triglycerides under Simulated Heating Conditions

Glycerol core aldehydes (GCAs) are significant nonvolatile aldehyde compounds generated in heated edible oils, which may pose potential health risks. Utilizing the complementary CID and EAD mass spectrometry data, this study introduced a predict-to-hit strategy, identifying 42 types of GCAs from oxidized OOO, LLL, and LnLnLn. Structural analysis revealed that oxidation occurred at both the sn-2 and sn-1/3 positions of triglyceride (TG), with the Sn-1/3 position exhibiting greater susceptibility as the degree of TG unsaturation increased. As the temperature increases, the concentration of saturated GCAs steadily rises, while unsaturated GCAs exhibit an initial increase, followed by a decrease. During further oxidation, GCAs tend to convert into hydroxyl compounds, monocyclic epoxides, dicyclic epoxides, and polycyclic epoxides, with epoxy groups predominantly forming at the 9,10 positions. These observations enhance our understanding of the formation of GCAs and promote the search for strategies to delay or prevent oxidation.

Investigation of the gastric digestion behavior of commercial infant formulae using an in vitro dynamic infant digestion model

The gastric digestion behavior of different commercial Stage 1 infant formulae (for 0-6 months) with different formulation backgrounds was investigated using an in vitro dynamic infant human gastric simulator (iHGS). The microstructural arrangements of the protein and lipid, colloidal stability and protein hydrolysis during digestion were elucidated. During gastric digestion, casein-dominant formulations showed a higher extent of aggregation due to their high proportion of casein micelles that underwent coagulation upon acidification and via the action of pepsin. The extensive protein coagulation/curd formation in casein-dominant infant formulae slowed the rate of protein hydrolysis and resulted in the retention of caseins in the iHGS for longer times. Confocal micrographs showed that oil droplets were entrapped in the curd particles of casein-dominant infant formulae, which consequently slowed the gastric emptying of lipids. Conversely, whey-dominant formulations showed a lower degree of protein aggregation that resulted in faster protein hydrolysis and rapid protein and lipid emptying from the iHGS. It was also revealed that whey-dominant infant formulae in the presence of biopolymers increased the viscosity of gastric chyme and induced the flocculation of oil droplets. This altered the rate of protein hydrolysis and emptying of lipids. Correlation analyses depicted the overall kinetics of gastric emptying of macronutrients during digestion and comprised two stages: (i) driven by the continuous stomach emptying and (ii) influenced by aggregation and coalescence indices. The present study highlights the similarities and differences in the digestion behaviors of commercial infant formulae based on important ingredients such as types of proteins and biopolymers, regardless of the formulation or processing histories.

Transcriptome and metabolome analyses reveal the effects of formula and breast milk on the growth and development of human small intestinal organoids

Breast milk is widely acknowledged as the ideal nutritional resource for infants and can well meet the nutritional requirements for baby's growth and development. Infant formula is a substitute for breast milk, designed to closely mimic its composition and function for breast milk. Most of the previous studies used tumor colorectal cancer cell lines to study the nutritional potency of formula and its components, so realistic data closer to the baby could not be obtained. Small intestinal organoids, derived from differentiated human embryonic stem cells, can be used to simulate nutrient absorption and metabolism in vitro. In this experiment, we used small intestinal organoids to compare the nutrient absorption and metabolism of three infant formulae for 0-6 months with breast milk samples. Transcriptome and metabolome sequencing methods were used to analyze the differentially expressed genes (DEGs) and differentially expressed metabolites (DEMs). The pathways related to DEGs, DEMs were enriched using GO, KEGG, GSEA and other methods to investigate their biological characteristics. We have found that both formula and breast milk promote the development of the infant's immune system, nutrient absorption and intestinal development. In PMH1 we found that the addition of oligofructose to milk powder promoted lipid metabolism and absorption. In PMH2 we found that whey protein powder favours the development of the immune system in infants. In PMH3 we found that oligogalactans may act on the brain-gut axis by regulating the intestinal flora, thereby promoting axon formation and neural development. By linking these biological properties of the milk powder with its composition, we confirmed the effects of added ingredients on the growth and development of infants. Also, we demonstrated the validity of small intestine organoids as a model for absorption and digestion in vitro. Through the above analyses, the advantages and disadvantages of the roles of formula and breast milk in the growth and metabolism of infants were also compared.

In vitro digestion and functional properties of bovine β-casein: A comparison between adults and infants

Gastrointestinal digestibility behavior, structural and functional characteristics of bovine β-casein (β-CN) were studied in vitro under infant and adult conditions. This direct comparison helps reveal the effects of different physiological stages on the digestive behavior of β-CN. Not only was the degree of hydrolysis (DH) of β-CN analyzed, but also the changes in its digestive morphology, microstructure, and secondary structure during digestion were explored in depth. Meanwhile, we focused on the physicochemical properties of β-CN digesta, including solubility, emulsifying and foaming properties, as well as their functional properties, such as antimicrobial and antioxidant activities. Key results showed that β-CN underwent more extensive hydrolysis in the adult digestion model, with approximately twice the DH compared to the infant model. The adult model exhibited faster digestion kinetics, less protein flocculation, and a more loosened secondary structure, indicating a more efficient digestion process. Notably, the digesta from the adult model displayed significantly improved solubility and emulsifying properties, and also enhanced antioxidant capacities, with significantly better inhibition of two common pathogenic bacteria than the infant model, and an average increase in the diameter of the inhibition zone of approximately 2 mm. These findings underscore the differential digestive behavior and functional potential of β-CN across physiological stages. This comprehensive assessment approach contributes to a more comprehensive insight into the digestive behavior of β-CN. Therefore, we conclude that producing products from unmodified β-CN may be more suitable for the adult population, and that the digesta in the adult model exhibit higher functional properties.

Using integrated transcriptomics and metabolomics to explore the effects of infant formula on the growth and development of small intestinal organoids

Infant formulas are designed to provide sufficient energy and the necessary nutrients to support the growth and development of newborns. Currently, research on the functions of formula milk powder focuses on clinical research and cell experiments, and there were many cell experiments that investigated the effect of infant formulas on cellular growth. However, most of the cells used are tumor cell lines, which are unable to simulate the real digestion process of an infant. In this study, we innovatively proposed a method that integrates human small intestinal organoids (SIOs) with transcriptomics and metabolomics analysis. We induced directed differentiation of human embryonic stem cells into SIOs and simulated the intestinal environment of newborns with them. Then, three kinds of 1-stage infant formulas from the same brand were introduced to simulate the digestion, absorption, and metabolism of the infant intestine. The nutritional value of each formula milk powder was examined by multi-omics sequencing methods, including transcriptomics and metabolomics analysis. Results showed that there were significant alterations in gene expression and metabolites in the three groups of SIOs after absorbing different infant formulas. By analyzing transcriptome and metabolome data, combined with GO, KEGG, and GSEA analysis, we demonstrated the ability of SIOs to model the different aspects of the developing process of the intestine and discovered the correlation between formula components and their effects, including Lactobacillus lactis and lactoferrin. The study reveals the effect and mechanisms of formula milk powder on the growth and development of infant intestines and the formation of immune function. Furthermore, our method can help to construct a multi-level assessment model, detect the effects of nutrients, and evaluate the interactions between nutrients, which is helpful for future research and development of infant powders.

sRAGE-binding and antimicrobial bioactivities of soy and pea protein after heating and in vitro infant digestion

During infant formula production, proteins are always heated, potentially affecting their digestibility and the bioactivities of resulting peptides. Although plant proteins are a promising dairy alternative for infant formula, they remain understudied, necessitating further investigations. Therefore, this research aimed to fill this gap by assessing the impact of different heating modes on soy protein (SP) and pea protein (PP), focusing on glycation levels, peptide formation during in vitro infant digestion, and immune protection potential (sRAGE-binding and antimicrobial activities) of the resulting peptides. Consequently, dry heating led to increased glycation and glycated peptide production, particularly with higher glycation in PP than SP. Moreover, PP exhibited an overall stronger sRAGE-binding capacity than SP, regardless of heating and digestion conditions. Regarding antimicrobial activity, both SP and PP-derived peptides displayed reduced effectiveness against Enterobacter cloacae after dry heating. Additionally, Staphylococcus epidermidis was differently inhibited, where PP-derived peptides showed inherent inhibition. The primary determinant of sRAGE-binding and antimicrobial potential in digestion-derived peptides was the protein source. Subsequent bioinformatics analysis predicted 519 and 133 potential antimicrobial peptides in SP and PP, respectively. This study emphasises the importance of protein source for infant formula to ensure infant health.

Alterations in the sequence and bioactivity of food-derived oligopeptides during simulated gastrointestinal digestion and absorption: a review

Food-derived oligopeptides (FOPs) exhibit various bioactivities. However, little was known about their sequence changes in the gastrointestinal tract and the effect of changes on bioactivities. FOPs' sequence features, changes and effects on bioactivities have been summarised. The sequence length of FOPs decreases with increased exposure of hydrophobic and basic amino acids at the terminal during simulated gastrointestinal digestion. A decrease in bioactivities after simulated intestinal absorption has correlated with a decrease of Leu, Ile, Arg, Tyr, Gln and Pro. The sequence of FOPs that pass readily through the intestinal epithelium corresponds to transport modes, and FOPs whose sequences remain unchanged after transport are the most bioactive. These include mainly dipeptides to tetrapeptides, consisting of numerous hydrophobic and basic amino acids, found mostly at the end of the peptide chain, especially at the C-terminal. This review aims to provide a foundation for applications of FOPs in nutritional supplements and functional foods.

In vitro gastrointestinal digestion methods of carbohydrate-rich foods

The trend toward healthier food products has led to an increase in the research of in vitro gastrointestinal digestion methods. Among the most used models, static models are the simplest. Most static models have three stages: oral, gastric, and intestinal, simulating the enzymatic, electrolyte, pH, temperature, and bile salt conditions. The studies that have taken the most notice are those related to antioxidant activity, followed by those dealing with proteins and carbohydrates using most of them static in vitro digestion models. The number of these studies has increased over the years, passing from 45 to 415 in a 10-year period (2012-2023) and showing an interest in knowing the impact of food on human health. Nevertheless, published papers report different methodologies and analytical approaches. This review discusses the similarities and differences between the published static in vitro gastrointestinal digestion methods, with a focus on carbohydrates, finding that the most used protocol is Infogest, but with differences, mainly in the type of enzymes and their activity. Regarding in vitro gastrointestinal digestion of carbohydrates, many of the published studies are related to food and biomacromolecules, being the oral phase the most omitted, while the intestinal phase in the most diverse. Other methodologies to study the intestinal phase have been recommended, but the number of in vitro digestion studies using these methodologies (RSIE and BBMV) is still scarce but could represent a good alternative to analyze carbohydrates foods when combining with Infogest. More studies are required in this area.

3-Monochloropropane-1,2-diol reduced bioaccessibility of sn-2 palmitate via binding with pancreatic lipase in infant formula during gastrointestinal digestion

Infant formula contains 3-monochloropropane-1,2-diol esters (3-MCPDE), which are formed during the deodorization step of vegetable oil refining. The European Food Safety Authority stated that 3-MCPDE can be hydrolyzed in the gastrointestinal tract to free-form 3-monochloropropane-1,2-diol (3-MCPD), which has potential toxicity and can be rapidly absorbed. Evaluating the effect of 3-MCPD on nutrition absorption is a prerequisite for establishing effective management strategies. A total of 66 crucial lipid molecules associated with 3-MCPD were identified based on debiased sparse partial correlation analysis. 3-MCPD affected triglyceride hydrolyzation and increased the concentration of undigested sn-2 palmitate (9.57 to 17.06 mg kg-1). 3-Monochloropropane-1,2-diol reduced the bioaccessibility of fatty acids, and more short- (31.42 to 58.02 mg kg-1) and medium-chain fatty acids (17.03 to 26.43 mg kg-1) remained unabsorbed. Lipidomic profiles of infant formula models spiked with different 3-MCPDE levels were investigated, and the results were consistent with the experiments with the commercial formula indicating lipid alteration was mainly affected by the digestive 3-MCPD. The formation of 3-MCPD ester-pancreatic lipase with the binding energy of -4.9 kcal mol-1 was more stable than triglyceride-pancreatic lipase (-4.0 kcal mol-1), affecting triglyceride hydrolyzation. 3-Monochloropropane-1,2-diol was bound to Glu13 and Asp331 residues of the pancreatic lipase via hydrogen bonds, which resulted in a conformational change of pancreatic lipase and spatial shielding effect. The existence of the spatial-shielding effect reduced the accessibility of pancreatic lipase and further affected triglyceride hydrolyzation. These findings indicated that 3-MCPD obstructed nutrient acquisition and laid the foundation for the subsequent nutrition enhancement design.

Novel trends and challenges in fat modification of next-generation infant formula: Considering the structure of milk fat globules to improve lipid digestion and metabolism of infants

Differences in the composition and structure of lipid droplets in infant formula (IF) and human milk (HM) can affect the fat digestion of infants, leading to high risk of metabolic diseases during later stages of growth. Recently, interest in simulating HM fat (HMF) has gradually increased due to its beneficial functions for infants. Much research focuses on the simulation of fatty acids and triacylglycerols. Enzymatic combined with new technologies such as carbodiimide coupling immobilization enzymes, solvent-free synthesis, and microbial fermentation can improve the yield of simulated HMF. Furthermore, fat modification in next-generation IF requires attention to the impact on the structure and function of milk fat globules (MFG). This review also summarizes the latest reports on MFG structure simulation, mainly related to the addition method and sequence of membrane components, and other milk processing steps. Although some of the simulated HMF technologies and products have been applied to currently commercially available IF, the cost is still high. Furthermore, understanding the fat decomposition of simulated HMF during digestion and assessing its nutritional effects on infants later in life is also a huge challenge. New process development and more clinical studies are needed to construct and evaluate simulated HMF in the future.

Comparative Analysis of Protein Digestion Characteristics in Human, Cow, Goat, Sheep, Mare, and Camel Milk under Simulated Infant Condition

An infant in vitro digestion model was utilized to investigate protein digestion characteristics in human and diverse mammalian milk (i.e., cow, goat, sheep, mare, and camel milk) using electrophoresis and chromatography. Digestive differences among milks were mainly manifested in the infant gastric phase, as evidenced by varying degrees of protein digestion. Notably, proteins (i.e., lactoferrin, serum albumin, and immunoglobulin G-heavy chain) remained partially intact in human milk, whereas these proteins in animal milk were exclusively degraded after gastrointestinal digestion. The peptide spectra of human, mare, and camel milk were highly similar, with a predominant formation of low-intensity small peptides, whereas the other three milk showed the opposite phenomenon. Heatmap cluster analysis indicated that camel milk was the most comparable to human milk before digestion, yet sheep milk was the most similar to human milk regarding protein digestion behaviors following infant gastric digestion.

Biomimetic Dispersive Solid-Phase Microextraction: A Novel Concept for High-Throughput Estimation of Human Oral Absorption of Organic Compounds

There is a quest for a novel in vitro analytical methodology that is properly validated for the prediction of human oral absorption and bioaccumulation of organic compounds with no need of animal models. The traditional log P parameter might not serve to predict bioparameters accurately inasmuch as it merely accounts for the hydrophobicity of the compound, but the actual interaction with the components of eukaryotic cells is neglected. This contribution proposes for the first time a novel biomimetic microextraction approach capitalized on immobilized phosphatidylcholine as a plasma membrane surrogate onto organic polymeric sorptive phases for the estimation of human intestinal effective permeability of a number of pharmaceuticals that are also deemed contaminants of emerging concern in environmental settings. A comprehensive exploration of the conformation of the lipid structure onto the surfaces is undertaken so as to discriminate the generation of either lipid monolayers or bilayers or the attachment of lipid nanovesicles. The experimentally obtained biomimetic extraction data is proven to be a superb parameter against other molecular descriptors for the development of reliable prediction models of human jejunum permeability with R2 = 0.76, but the incorporation of log D and the number of aromatic rings in multiple linear regression equations enabled improved correlations up to R2 = 0.88. This work is expected to open new avenues for expeditious in vitro screening methods for oral absorption of organic contaminants of emerging concern in human exposomics.

Cell factory-based milk protein biomanufacturing: Advances and perspectives

The increasing global population and protein demand cause global challenges for food supply. Fueled by significant developments in synthetic biology, microbial cell factories are constructed for the bioproduction of milk proteins, providing a promising approach for scalable and cost-effective production of alternative proteins. This review focused on the synthetic biology-based microbial cell factory construction for milk protein bioproduction. The composition, content, and functions of major milk proteins were first summarized, especially for caseins, α-lactalbumin, and β-lactoglobulin. An economic analysis was performed to determine whether cell factory-based milk protein production is economically viable for industrial production. Cell factory-based milk protein production is proved to be economically viable for industrial production. However, there still exist some challenges for cell factory-based milk protein biomanufacturing and application, including the inefficient production of milk proteins, insufficient investigation of protein functional property, and insufficient food safety evaluation. Constructing new high-efficiency genetic regulatory elements and genome editing tools, coexpression/overexpression of chaperone genes, and engineering protein secretion pathways and establishing a cost-effective protein purification method are possible ways to improve the production efficiency. Milk protein biomanufacturing is one of the promising approaches to acquiring alternative proteins in the future, which is of great importance for supporting cellular agriculture.

Bioimprinted lipase-catalyzed synthesis of medium- and long-chain structured lipids rich in docosahexaenoic acid for infant formula

Medium- and long-chain structured lipids (MLSLs) rich in docosahexaenoic acid (DHA) were obtained in shorter reaction time by acidolysis of single-cell oil (DHASCO) from Schizochytrium sp. with caprylic acid (CA) using a lipase bioimprinted with fatty acids as a catalyst. The conditions for preparation of the bioimprinted lipase for the acidolysis reaction were firstly optimized and the activity of the obtained lipase was 2.17 times higher than that of the non-bioimprinted. The bioimprinted lipase was then used as a catalyst and the reaction conditions were optimized. Under the optimal conditions, the equilibrium could be achieved in 4 h, and the total and sn-1,3 CA contents in the product were 29.18% and 42.34%, respectively, and the total and sn-2 DHA contents were 46.26% and 70.12%, respectively. Such MLSLs rich in sn-1,3 CA and sn-2 DHA are beneficial for DHA absorption, and thus have potential for use in infant formula.

Design, Evaluation and Comparison of Nanostructured Lipid Carriers and Chitosan Nanoparticles as Carriers of Poorly Soluble Drugs to Develop Oral Liquid Formulations Suitable for Pediatric Use

There is a serious need of pediatric drug formulations, whose lack causes the frequent use of extemporaneous preparations obtained from adult dosage forms, with consequent safety and quality risks. Oral solutions are the best choice for pediatric patients, due to administration ease and dosage-adaptability, but their development is challenging, particularly for poorly soluble drugs. In this work, chitosan nanoparticles (CSNPs) and nanostructured lipid carriers (NLCs) were developed and evaluated as potential nanocarriers for preparing oral pediatric solutions of cefixime (poorly soluble model drug). The selected CSNPs and NLCs showed a size around 390 nm, Zeta-potential > 30 mV, and comparable entrapment efficiency (31-36%), but CSNPs had higher loading efficiency (5.2 vs. 1.4%). CSNPs maintained an almost unchanged size, homogeneity, and Zeta-potential during storage, while NLCs exhibited a marked progressive Zeta-potential decrease. Drug release from CSNPs formulations (differently from NLCs) was poorly affected by gastric pH variations, and gave rise to a more reproducible and controlled profile. This was related to their behavior in simulated gastric conditions, where CSNPs were stable, while NLCs suffered a rapid size increase, up to micrometric dimensions. Cytotoxicity studies confirmed CSNPs as the best nanocarrier, proving their complete biocompatibility, while NLCs formulations needed 1:1 dilution to obtain acceptable cell viability values.

The Protein Composition and In Vitro Digestive Characteristics of Animal- versus Plant-Based Infant Nutritional Products

The protein composition and digestive characteristics of four commercially available infant formulae (IF) manufactured using bovine (B-IF), caprine (C-IF), soy (S-IF), and rice (R-IF) as a protein source were examined in this study. Plant-based formulae had significantly higher crude protein and non-protein nitrogen (NPN) concentrations. Static in vitro gastrointestinal digestion of these formulae, and subsequent analysis of their digestates, revealed significantly higher proteolysis of B-IF at the end of gastrointestinal digestion compared to the other formulae, as indicated by the significantly higher concentration of free amine groups. Furthermore, differences in structure formation during the gastric phase of digestion were observed, with formation of a more continuous, firmer coagulum by C-IF, while R-IF demonstrated no curd formation likely due to the extensive hydrolysis of these proteins during manufacture. Differences in digestive characteristics between formulae manufactured from these different protein sources may influence the bio-accessibility and bioavailability of nutrients, warranting additional study.

Efficient in vitro digestion of lipids and proteins in bovine milk fat globule membrane ingredient (MFGMi) and whey-casein infant formula with added MFGMi

The relative immaturity of the infant digestive system has the potential to affect the bioavailability of dietary lipids, proteins, and their digested products. We performed a lipidomic analysis of a commercial bovine milk fat globule membrane ingredient (MFGMi) and determined the profile of lipids and proteins in the bioaccessible fraction after in vitro digestion of both the ingredient and whey-casein-based infant formula without and with MFGMi. Test materials were digested using a static 2-phase in vitro model, with conditions simulating those in the infant gut. The extent of digestion and the bioaccessibility of various classes of neutral and polar lipids were monitored by measuring a wide targeted lipid profile using direct infusion-mass spectrometry. Digestion of abundant proteins in the ingredient and whey-casein infant formula containing the ingredient was determined by denaturing PAGE with imaging of Coomassie Brilliant Blue stained bands. Cholesterol esters, diacylglycerides, triacylglycerides, phosphatidylcholines, and phosphatidylethanolamines in MFGMi were hydrolyzed readily during in vitro digestion, which resulted in marked increases in the amounts of free fatty acids and lyso-phospholipids in the bioaccessible fraction. In contrast, sphingomyelins, ceramides, and gangliosides were largely resistant to simulated digestion. Proteins in MFGMi and the infant formulas also were hydrolyzed efficiently. The results suggest that neutral lipids, cholesterol esters, phospholipids, and proteins in MFGMi are digested efficiently during conditions that simulate the prandial lumen of the stomach and small intestine of infants. Also, supplementation of whey-casein-based infant formula with MFGMi did not appear to alter the profiles of lipids and proteins in the bioaccessible fraction after digestion.

An in vitro protocol to characterise the resistance of food proteins to intestinal digestion

In vitro digestion tests provide data on the form in which dietary proteins maybe presented to the gut mucosal immune system, one of many strands of evidence used in allergenicity risk assessment. A 96-well plate format in vitro intestinal digestion protocol has been developed with a high and low enzyme activity test executed at pH 6.5 and 8.0. It was applied to the systematic analysis of test proteins (including six allergens and one non-allergenic comparator) which were either completely resistant to pepsinolysis or gave rise to large persistent fragments following in vitro gastric digestion. Digestion was monitored using SDS-PAGE and densitometry. Proteins resistant to pepsin were also resistant to intestinal digestion irrespective of the protocol applied and gave rise to large persistent digestion fragments. In contrast persistent fragments from pepsin digestion were readily digested. Bile salts enhanced the digestibility of two highly resistant proteins, lysozyme ad β-lactoglobulin, changing the rank order of protein digestibility. Intestinal digestion tests that include bile salts provide a more physiologically relevant system for future investigation into how digestion products may influence the balance between tolerance and sensitization - and hence contribute to future development of a more effective allergenicity risk assessment process.

Formulation, pilot-scale preparation, physicochemical characterization and digestibility of a lentil protein-based model infant formula powder

BACKGROUND

Infant formula is a human milk substitute for consumption during the first months of life. The protein component of such products is generally of dairy origin. Alternative sources of protein, such as those of plant origin, are of interest due to dairy allergies, intolerances, and ethical and environmental considerations. Lentils have high levels of protein (20-30%) with a good amino acid profile and functional properties. In this study, a model lentil protein-based formula (LF), in powder format, was produced and compared to two commercial plant-based infant formulae (i.e., soy; SF and rice; RF) in terms of physicochemical properties and digestibility.

RESULTS

The macronutrient composition was similar between all the samples; however, RF and SF had larger volume-weighted mean particle diameters (D[4,3] of 121-134 μm) than LF (31.9 μm), which was confirmed using scanning electron and confocal laser microscopy. The larger particle sizes of the commercial powders were attributed to their agglomeration during the drying process. Regarding functional properties, the LF showed higher D[4,3] values (17.8 μm) after 18 h reconstitution in water, compared with the SF and RF (5.82 and 4.55 μm, respectively), which could be partially attributed to hydrophobic protein-protein interactions. Regarding viscosity at 95 °C and physical stability, LF was more stable than RF. The digestibility analysis showed LF to have similar values (P < 0.05) to the standard SF.

CONCLUSION

These results demonstrated that, from the nutritional and physicochemical perspectives, lentil proteins represent a good alternative to other sources of plant proteins (e.g., soy and rice) in infant nutritional products. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Starch Digestion in Infants: An Update of Available In Vitro Methods-A Mini Review

Complementary feeding starts at around six months of age because neither breast milk nor formula assure the proper nutrition of infants. Therefore, along with breast milk, solid foods are gradually introduced, particularly cereal-based foods, which will provide starch as a new source of energy and nutrients. As a result, the need of an adequate in vitro digestion method to study the influence of different aspects of weaning period is unquestionable. This critical review summarizes the in vitro digestion methods available for the analysis of starch hydrolysis under infant conditions considering different features, namely, starch digestion, infant digestive conditions and in vitro models suitable for the study of starch digestion (static, semi-dynamic and dynamic). Key factors such as enzyme concentrations, transit time, oral, gastric and intestinal conditions and differences with current adult models, have been addressed. The need for standardized infant digestion models adapted to the complementary feeding period was discussed. Existing literature data demonstrate that more effort has to be done to improve the research on this issue, in order to obtain comparable results that would address a better understanding of the digestibility of different food nutrients under infant conditions facilitating the development of appropriate formulations that may assure proper infant nutrition.

Effects of mono- and di-glycerides/phospholipids (MDG/PL) on the bioaccessibility of lipophilic nutrients in a protein-based emulsion system

Lipophilic nutrients are known to have relatively poor absorption, thus limiting their bioaccessibility. Consequently, researchers in food and pharmaceutical areas are exploring different techniques to promote the efficient delivery of lipophilic nutrients. The effects of two polar lipids, namely mono-, di-glycerides (MDG) and lecithin (PL), on the bioaccessibility of lipophilic nutrients were investigated in this study with a protein-based emulsion model system. During the emulsion preparation and formation, the incorporation of MDG/PL was found to benefit the dissolution and stabilization of lipophilic nutrients, such as lutein, and could also modify the construction of the emulsion surface. An in vitro digestion study showed that the use of MDG/PL could significantly increase the bioaccessibility of lipophilic nutrients [lutein, vitamin E, and docosahexaenoic acid (DHA)] by 13.52%, 186.90%, and 36.17% in a protein-based emulsion system. The use of MDG and PL decreased the interfacial tension in all the samples: protein only 20.65 mN m^-1, protein-PL 6.47 mN m^-1, and protein-MDG/PL 4.23 mN m^-1, as well as 12.11 mN m^-1, 1.26 mN m^-1 and 1.16 mN m^-1 with the presence of bile salts. Caco-2 cell culture results showed that, with the application of MDG/PL, the absorption rate of micelles was higher than that in the other groups and this resulted in a 70% absorption increase for lutein. Therefore, MDG/PL can improve the lipophilic nutrient absorption via promoting the affinity of formed micelles to the enterocytes of the small intestine. This study exhibited the effectiveness of MDG/PL on improving the bioaccessibility of lipophilic nutrients in a protein-based emulsion system mimicking the digestion and absorption fate of breast milk in an infant's gastric intestinal tract, thus suggesting that MDG/PL can be used as a technical pathway to improve the absorption of lipophilic nutrients.

In vitro Digestion Characteristics of Hydrolyzed Infant Formula and Its Effects on the Growth and Development in Mice

Infant formula, an important food for babies, is convenient and nutritious, and hydrolyzed formulas have attracted much attention due to their non-allergicity. However, it is uncertain whether hydrolyzed formulars cause obesity and other side effects in infants. Herein, three infant formulas, standard (sIF), partially hydrolyzed (pHIF), and extensively hydrolyzed (eHIF), were analyzed in an in vitro gastrointestinal digestion model. With increasing degree of hydrolysis, the protein moleculars, and allergenicity of the proteins decreased and the long-chain polyunsaturated fatty acid content increased. Moreover, the digestion model solutions quickly digested the small fat globules and proteins in the hydrolyzed formula, allowing it to become electrostatically stable sooner. The eHIF-fed mice presented larger body sizes, and exhibited excellent exploratory and spatial memory abilities in the maze test. Based on villus height and crypt depth histological characterizations and amplicon sequencing, eHIF promoted mouse small intestine development and changed the gut microbiota composition, eventually favoring weight gain. The mouse spleen index showed that long-term infant formula consumption might be detrimental to immune system development, and the weight-bearing swimming test showed that eHIF could cause severe physical strength decline. Therefore, long-term consumption of infant formula, especially eHIF, may have both positive and negative effects on mouse growth and development, and our results might shed light on feeding formula to infants.

Lactobacillus crispatus Strain KT-11 S-Layer Protein Inhibits Rotavirus Infection

S-layer proteins (SLPs), which are present in the external layer of certain strains of lactic acid bacteria isolated from the intestinal tract, are known to recognize and bind to specific proteins and glycan structures and contribute to adsorption to the host intestinal mucosa. The binding properties of certain SLPs are considered to exert a competitive inhibitory effect on infection because similar properties are involved in the infection mechanisms of several viruses. However, little is known regarding whether SLPs directly inhibit viral infection. In the present study, we investigated the effect of an SLP of the Lactobacillus crispatus KT-11 strain, a probiotic strain isolated from a healthy human infant, on human rotavirus infection. The impact of KT-11 lithium chloride extract (KT-11 LE), which contains SLP, on the infection of the P[4] genotype human rotavirus strain DS-1 was evaluated by monitoring the amplification of viral protein 6 (VP6) expression in human intestinal epithelial Caco-2 cells by quantitative reverse transcription-polymerase chain reaction assay after infection. KT-11 LE showed a significant suppressive effect on DS-1 infection in a dose-dependent manner with pre-infection treatment, whereas post-infection treatment was not effective. A 45 KDa protein isolated from KT-11 LE was investigated for homology using the BLAST database and was found to be a novel SLP. KT-11 SLP concentrate (KT-11 SLP) significantly inhibited the proliferative process of the DS-1 strain but not that of the P[8] genotype human rotavirus strain Wa. KT-11 SLP exerted significant inhibitory effect on DS-1 infection by pre-infection treatment even after digestion with gastric juice up to 2 h. Our results provided crucial evidence that SLPs from certain Lactobacillus strains can inhibit human rotavirus infection of intestinal epithelial cells.

Recent Advances in Novel Packaging Technologies for Shelf-Life Extension of Guava Fruits for Retaining Health Benefits for Longer Duration

Guava (Psidium guajava L.) fruit is also known as the apple of tropics, belongs to the family of genus Psidium, and is widely cultivated in tropical zones of the world. Recently, the importance of guava fruit has increased due to its inherent nutritional content, pleasant aroma, excellent flavor, and delicious taste. It is considered an excellent source of nutrients and phytochemicals. Guava is a climacteric fruit that continues to mature or ripen even after harvest, showing an increase in the rate of respiration and metabolic activities within a short period, leading to rapid senescence or spoilage of fruit. It has limitations in terms of commercialization due to short storage life after harvest and sensitivity to diseases and chilling injury during the storage period. Many postharvest technologies such as edible packaging, modified atmosphere packaging (MAP), composite packaging, controlled atmosphere packaging (CAP), antimicrobial/antifungal packaging, and nano packaging have been used to retard the chilling injury and enhance the keeping quality of guava fruits during the storage period to control respiration rate, reduce weight loss, minimize lipid oxidation, and maintain organoleptic properties. However, these packaging technologies have varied effects on the internal and external quality attributes of guava fruits. This review, therefore, discusses the physiology, mechanism of ripening, oxidation, and ethylene production of guava fruits. The review also discusses the packaging technologies and their effect on the postharvest characteristics of guava fruits during the storage period.

A Comparative Analysis of Lipid Digestion in Human Milk and Infant Formulas Based on Simulated In Vitro Infant Gastrointestinal Digestion

To investigate the lipid digestive behaviors of human and infant formulas and analyze the differences between them, we investigated the fat globule particle size distribution, lipolysis rate, and fatty acid release of infant formulas with different fat sources and human milk using an in vitro infant digestion model. The results suggested that the particle size in infant formula increased rapidly during gastric digestion and decreased significantly after intestinal digestion, whereas the particle size in human milk increased slowly during gastric digestion but increased rapidly during intestinal digestion (p < 0.05). Despite having a larger droplet size, human milk demonstrated a very high lipolysis rate due to the presence of MFGM. In terms of the distribution of fatty acids in digestion products, the proportion of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs) in vegetable oil-based infant formulas was close to that of human milk. The amount of SFAs in milk fat-based infant formulas was significantly higher than that in human milk, and the content of MUFAs in all infant formulas was significantly lower than that in human milk (p < 0.05). After digestion, the most abundant fatty acid released by human milk was C18:2n6c, while the fatty acids released by infant formulas were SFAs, such as C14:0, C16:0, and C18:0.

Compositional and Functional Considerations for Bovine-, Caprine- and Plant-Based Infant Formulas

Breastmilk is the optimal source of nutrition for infants. However, in circumstances where breastfeeding is not possible or feasible, infant formula provides an essential alternative to fulfil the nutritional requirements of the developing infant. Traditionally, the manufacture of infant formula has involved utilisation of bovine milk as a base ingredient, formulated with other nutrients and bioactive ingredients to closely match the composition of human breastmilk. While it is the most widely available type of formula on the market, bovine-based infant formula is not suitable for all infants, and therefore alternatives such as those based on caprine milk, soy and rice protein are becoming increasingly available. This review provides a detailed examination of the composition of infant formula prepared from bovine milk, caprine milk, soy, and rice protein sources. Available literature on nutrient bio-accessibility and aspects of protein functionality relevant to infant formula is discussed.

Application of ultrasound treatment for improving the quality of infant meat puree

Infant meat puree has an indispensable effect on the oral development and nutritional intake of infants. However, commercially available products have poor texture and relatively low digestibility. In this study, ultrasound (20 kHz and 200 W, 400 W, or 600 W) was applied to the pretreatment of raw meat for preparing infant meat puree for 15 min, 30 min, and 45 min. To assess the impact of ultrasound on infant meat puree, the viscosity, texture, water distribution, particle size and in vitro digestibility were determined. The results showed that, compared with control, viscosity and hardness of meat puree decreased and the texture was better in 400 W and 600 W groups. The content of immobilized water increased in comparison with the control. Ultrasound had no obvious effect on the digestibility of meat puree in gastric phase, but it increased the digestibility in intestinal phase with the highest digestibility (80.85%±3.33) in 600 W, 15 min group. Overall, the ultrasound parameters of 600 W for 15 min can be selected as the best condition to process infant meat puree. The findings provide a new perspective for the improvement of infant meat puree.

Comparative Analysis of Lipid Digestion Characteristics in Human, Bovine, and Caprine Milk Based on Simulated In Vitro Infant Gastrointestinal Digestion

Lipid digestion characteristics in human, bovine, and caprine milk were investigated using an infant in vitro digestion model. Our results suggested that particle size in bovine and caprine milk increased initially and then decreased over time, whereas the particle size in human milk continuously decreased. The lipolysis degree of human milk (86.8%) was higher than that in bovine (80.2%) and caprine (82.7%) milk (P < 0.05). Compared to human milk, bovine and caprine milk released higher unsaturated fatty acids and lower SFAs. In addition, 12 and 84 glyceride species were significantly different between bovine and human milk, during gastrointestinal digestion (P < 0.05). Another 13 and 92 glyceride species were found to be significantly different between caprine and human milk. A total of 30 and 31 lipids were screened as biomarkers to further clarify the differences related to lipid digestion properties of human, bovine, and caprine milk.

Structure-Specific Fermentation of Galacto-Oligosaccharides, Isomalto-Oligosaccharides and Isomalto/Malto-Polysaccharides by Infant Fecal Microbiota and Impact on Dendritic Cell Cytokine Responses

SCOPE

Next to galacto-oligosaccharides (GOS), starch-derived isomalto-oligosaccharide preparation (IMO) and isomalto/malto-polysaccharides (IMMP) could potentially be used as prebiotics in infant formulas. However, it remains largely unknown how the specific molecular structures of these non-digestible carbohydrates (NDCs) impact fermentability and immune responses in infants.

METHODS AND RESULTS

In vitro fermentation of GOS, IMO and IMMP using infant fecal inoculum of 2- and 8-week-old infants shows that only GOS and IMO are fermented by infant fecal microbiota. The degradation of GOS and IMO coincides with an increase in Bifidobacterium and production of acetate and lactate, which is more pronounced with GOS. Individual isomers with an (1↔1)-linkage or di-substituted reducing terminal glucose residue are more resistant to fermentation. GOS, IMO, and IMMP fermentation digesta attenuates cytokine profiles in immature dendritic cells (DCs), but the extent is dependent on the infants age and NDC structure.

CONCLUSION

The IMO preparation, containing reducing and non-reducing isomers, shows similar fermentation patterns as GOS in fecal microbiota of 2-week-old infants. Knowledge obtained on the substrate specificities of infant fecal microbiota and the subsequent regulatory effects of GOS, IMO and IMMP on DC responses might contribute to the design of tailored NDC mixtures for infants of different age groups.

Guidance on risk assessment of nanomaterials to be applied in the food and feed chain: human and animal health

The EFSA has updated the Guidance on risk assessment of the application of nanoscience and nanotechnologies in the food and feed chain, human and animal health. It covers the application areas within EFSA's remit, including novel foods, food contact materials, food/feed additives and pesticides. The updated guidance, now Scientific Committee Guidance on nano risk assessment (SC Guidance on Nano-RA), has taken account of relevant scientific studies that provide insights to physico-chemical properties, exposure assessment and hazard characterisation of nanomaterials and areas of applicability. Together with the accompanying Guidance on Technical requirements for regulated food and feed product applications to establish the presence of small particles including nanoparticles (Guidance on Particle-TR), the SC Guidance on Nano-RA specifically elaborates on physico-chemical characterisation, key parameters that should be measured, methods and techniques that can be used for characterisation of nanomaterials and their determination in complex matrices. The SC Guidance on Nano-RA also details aspects relating to exposure assessment and hazard identification and characterisation. In particular, nanospecific considerations relating to in vitro/in vivo toxicological studies are discussed and a tiered framework for toxicological testing is outlined. Furthermore, in vitro degradation, toxicokinetics, genotoxicity, local and systemic toxicity as well as general issues relating to testing of nanomaterials are described. Depending on the initial tier results, additional studies may be needed to investigate reproductive and developmental toxicity, chronic toxicity and carcinogenicity, immunotoxicity and allergenicity, neurotoxicity, effects on gut microbiome and endocrine activity. The possible use of read-across to fill data gaps as well as the potential use of integrated testing strategies and the knowledge of modes or mechanisms of action are also discussed. The Guidance proposes approaches to risk characterisation and uncertainty analysis.

Multifunctional Lipid-Based Nanoparticles for Codelivery of Anticancer Drugs and siRNA for Treatment of Non-Small Cell Lung Cancer with Different Level of Resistance and EGFR Mutations

Resistance to chemotherapy, enhanced proliferation, invasion, angiogenesis, and metastasis (RPIAM) represent major obstacles that limit the efficacy of cancer treatment especially in advanced stages of cancer. Overcoming or suppressing RPIAM can dramatically improve the treatment outcome. Non-small cell lung cancer (NSCLC) is frequently diagnosed in an advanced stage and often possesses intrinsic resistance to chemotherapy accompanied by the fast development of acquired resistance during the treatment. Oncogenic receptor tyrosine kinases (TKs), specifically epidermal growth factor (EGF) TKs, play an important role in the activation of MAPK/PI3K/Akt/STAT pathways, finally leading to the development of RPIAM. However, the suppression of EGF-TK by different drugs is limited by various defensive mechanisms and mutations. In order to effectively prevent the development of RPIAM in NSCLC, we formulated and tested a multicomponent and multifunctional cancer targeted delivery system containing Nanostructured Lipid Carriers (NLCs) as vehicles, luteinizing hormone release hormone (LHRH) as a cancer targeting moiety, EFG-TK inhibitor gefitinib and/or paclitaxel as anticancer drug(s), siRNA targeted to EGF receptor (EGFR) mRNA as a suppressor of EGF receptors, and an imaging agent (rhodamine) for the visualization of cancer cells. Experimental data obtained show that this complex delivery system possesses significantly enhanced anticancer activity that cannot be achieved by individual components applied separately.

In vitro models of gut digestion across childhood: current developments, challenges and future trends

The human digestion is a multi-step and multi-compartment process essential for human health, at the heart of many issues raised by academics, the medical world and industrials from the food, nutrition and pharma fields. In the first years of life, major dietary changes occur and are concomitant with an evolution of the whole child digestive tract anatomy and physiology, including colonization of gut microbiota. All these phenomena are influenced by child exposure to environmental compounds, such as drugs (especially antibiotics) and food pollutants, but also childhood infections. Due to obvious ethical, regulatory and technical limitations, in vivo approaches in animal and human are more and more restricted to favor complementary in vitro approaches. This review summarizes current knowledge on the evolution of child gut physiology from birth to 3 years old regarding physicochemical, mechanical and microbial parameters. Then, all the available in vitro models of the child digestive tract are described, ranging from the simplest static mono-compartmental systems to the most sophisticated dynamic and multi-compartmental models, and mimicking from the oral phase to the colon compartment. Lastly, we detail the main applications of child gut models in nutritional, pharmaceutical and microbiological studies and discuss the limitations and challenges facing this field of research.

Bioactive Compounds in Infant Formula and Their Effects on Infant Nutrition and Health: A Systematic Literature Review

Infant formulas are an alternative to replace or supplement human milk when breastfeeding is not possible. The knowledge of human milk's bioactive compounds and their beneficial effects has attracted the interest of researchers in the field of infant nutrition, as well as researchers of technology and food sciences that seek to improve the nutritional characteristics of infant formulas. Several scientific studies evaluate the optimization of infant formula composition. The bioactive compound inclusion has been used to upgrade the quality and nutrition of infant formulas. In this context, the purpose of this systematic literature review is to assess the scientific evidence of bioactive compounds present in infant formulas (α-lactalbumin, lactoferrin, taurine, milk fat globule membrane, folates, polyamines, long-chain polyunsaturated fatty acids, prebiotics, and probiotics) and their effects on infant nutrition and health. Through previously determined criteria, studies published in the last fifteen years from five different databases were included to identify the advances in the optimization of infant formula composition. Over the last few years, there has been optimization of the infant formula composition, not only to increase the similarities in their content of macro and micronutrients but also to include novel bioactive ingredients with potential health benefits for infants. Although the infant food industry has advanced in the last years, there is no consensus on whether novel bioactive ingredients added to infant formulas have the same functional effects as the compounds found in human milk. Thus, further studies about the impact of bioactive compounds in infant nutrition are fundamental to infant health.

Gastric protein digestion of goat and cow milk infant formula and human milk under simulated infant conditions

The protein digestion kinetics of goat milk infant formula (GMF) is previously shown to be more comparable to that of human milk (HM) than cow milk infant formula (CMF). To evaluate whether gastric behaviour contributes to differences in protein digestion kinetics, fresh HM, a GMF and a CMF were subjected to in vitro gastric digestion simulating infant conditions. Coagulation behaviour, particle size distribution and viscosity of the digesta were evaluated. After centrifugation of the digesta, total solids and protein distribution, and protein hydrolysis in the cream, serum and pellet fraction were investigated. The GMF and CMF were in general similar with respect to physicochemical and protein breakdown properties. However, a number of notable differences in physicochemical behaviour were observed, which may contribute to faster initial protein digestion of GMF. HM behaved differently from both formulas. These differences provide new insights into the possibilities for improvement of infant formulas.

Advances of plant-based structured food delivery systems on the in vitro digestibility of bioactive compounds

Food researchers are currently showing a growing interest in in vitro digestibility studies due to their importance for obtaining food products with health benefits and ensuring a balanced nutrient intake. Various bioactive food compounds are sensitive to the digestion process, which results in a lower bioavailability in the gut. The main objective of structured food delivery systems is to promote the controlled release of these compounds at the desired time/place, in addition to protecting them during digestion processes. This review provides an overview of the influence of structured delivery systems on the in vitro digestive behavior. The main delivery systems are summarized, the pros and cons of different structures are outlined, and examples of several studies that optimized the use of these structured systems are provided. In addition, we have reviewed the use of plant-based systems, which have been of interest to food researchers and the food industry because of their health benefits, improved sustainability as well as being an alternative for vegetarian, vegan and consumers suffering from food allergies. In this context, the review provides new insights and comprehensive knowledge regarding the influence of plant-based structured systems on the digestibility of encapsulated compounds and proteins/polysaccharides used in the encapsulation process.

Effects of recombinant human gastric lipase and pancreatin during in vitro pediatric gastro-intestinal digestion

The aim of the study was to implement a gastric digestion step using recombinant human gastric lipase (rHGL) in an in vitro pediatric gastro-intestinal digestion model to achieve a physiologically relevant gastric contribution to total gastro-intestinal lipid digestion. A commercial infant formula (NAN Comfort stage 1 (NAN1)) with 3.4% lipid and an in-lab prepared oil-in-water emulsion, emulsified with soy phosphatidylcholine (SPCemul), with 3.5% lipid (oil-blend containing Akonino NS, MEG-3 and ARASCO oils) were subjected to in vitro gastro-intestinal digestion. To achieve a physiologically relevant level of gastric digestion, 50 min of in vitro gastric digestion, using either 0, 3.75 or 7.5 TBU mL^-1 rHGL, was followed by 90 min of in vitro intestinal digestion, using either 0 or 26.5 TBU mL^-1 pancreatic triglyceride lipase (PTL) from porcine pancreatin. The digestion of the substrates was assessed using titration-based quantification supported by HPLC-ELSD analysis. In vitro gastric digestion of NAN1 and SPCemul with either 3.75 or 7.5 TBU mL^-1 rHGL contributed with 10-27% of the total gastro-intestinal digestion, corresponding to the reported contribution in human infants. At the end of the gastro-intestinal digestion (t = 140 min), the combined lipolytic effect of rHGL and PTL was additive during digestion of SPCemul, but not for the digestion of NAN1, as all lipase activity combinations resulted in a similar degree of NAN1 digestion. The effect of gastric digestion with rHGL on total digestion therefore appeared to be substrate dependent. To conclude, a gastric digestion step using rHGL resulting in physiologically relevant gastric contribution to the observed gastro-intestinal digestion was successfully implemented into an in vitro pediatric gastro-intestinal digestion model.

Evidence from Neonatal Piglets Shows How Infant Formula and Other Mammalian Milk Shape Lipid Metabolism

We tested the hypothesis that the consumption of different milk lipids is one of the factors affecting metabolic response to lipid in the early life of infants. Neonatal piglets, as animal models, were stratified by the feeding mode (formula-fed, bovine-, caprine-, and human milk-fed). Lipidomic profiles of plasma and liver samples were detected using liquid chromatography-mass spectrometry (LC-MS). The results indicate that 31, 54, and 28 differential lipid species could be used as potential biomarkers for bovine milk, caprine milk, and infant formula-fed samples, respectively, and the main lipid classes screened in plasma were SM, PC, and PE, including PC(14:1/P-20:0) as the isoform of PC(34:1), which regulates the lipid metabolism gene peroxisome proliferator-activated receptor α, PPAR-α. SM(d15:1/22:0) was the common potential biomarker screened from all of the groups. The amounts of biomarkers screened from the caprine milk-fed liver samples were the highest, which had a significant effect on the distribution of SM, PI, and PA. Infant formula, bovine-, and caprine milk-fed samples had an obvious effect on the metabolism of glycerophospholipid and glycerol ester, especially TG (16:0/18:0/18:2).

Lipid Composition, Digestion, and Absorption Differences among Neonatal Feeding Strategies: Potential Implications for Intestinal Inflammation in Preterm Infants

Necrotizing enterocolitis (NEC) is a significant cause of morbidity and mortality in the neonatal population. Formula feeding is among the many risk factors for developing the condition, a practice often required in the cohort most often afflicted with NEC, preterm infants. While the virtues of many bioactive components of breast milk have been extolled, the ability to digest and assimilate the nutritional components of breast milk is often overlooked. The structure of formula differs from that of breast milk, both in lipid composition and chemical configuration. In addition, formula lacks a critical digestive enzyme produced by the mammary gland, bile salt-stimulated lipase (BSSL). The gastrointestinal system of premature infants is often incapable of secreting sufficient pancreatic enzymes for fat digestion, and pasteurization of donor milk (DM) has been shown to inactivate BSSL, among other important compounds. Incompletely digested lipids may oxidize and accumulate in the distal gut. These lipid fragments are thought to induce intestinal inflammation in the neonate, potentially hastening the development of diseases such as NEC. In this review, differences in breast milk, pasteurized DM, and formula lipids are highlighted, with a focus on the ability of those lipids to be digested and subsequently absorbed by neonates, especially those born prematurely and at risk for NEC.

Freezing-then-aging treatment improved the protein digestibility of beef in an in vitro infant digestion model

In vitro protein digestibility of freezing-then-aged beef was investigated in an infant digestion model. The treatments were divided into freezing-then-aging (FA) and aging-only (AO) groups. Carbonyl and total free sulfhydryl contents were the same between both groups for 14-day aging. Freezing had no effect on beef myofibrillar protein tertiary structure. Although caspase-3 activity did not differ, the FA group showed higher cathepsin B activity than the AO group (p < 0.05). The 10% trichloroacetic acid-soluble α-amino content was higher in FA than AO group, on aging day 14 (p < 0.05). Post in vitro digestion of beef aged for 14 days, the FA group had a higher content, than the AO group, of α-amino groups and proteins digested under 3 kDa (p < 0.05). An electrophoretogram of the digesta showed improved digestion of actin in the FA group. Collectively, the freezing-then-aging process enhanced the protein digestibility of beef in this in vitro infant digestion model.

Biological transformation of chlorophyll-rich spinach (Spinacia oleracea L.) extracts under in vitro gastrointestinal digestion and colonic fermentation

Chlorophyll can be obtained from a variety of green vegetables. In this study, chlorophyll-rich spinach (Spinacia oleracea L.) extracts were subjected to early-life and adult-life gastrointestinal digestion and colonic fermentation in a murine model in vitro to investigate the biological transformation of the chlorophyll. Chlorophylls a and b were the main compounds present in the extracts. Furthermore, some other compounds were also confirmed, such as 15¹-hydroxy-lactone chlorophyll a, 13²-hydroxy chlorophyll a, and 15¹-hydroxy-lactone chlorophyll b. Chlorophylls favored pheophytinization and oxidative reactions under in vitro early-life and adult-life gastrointestinal digestion, leading to the formation of pheophytin a, pheophytin b, 13²-hydroxy pheophytin a, and 15¹-hydroxy-lactone pheophytin a. 16S rRNA gene sequencing conveyed that pheophytins modulated the gut microbiota composition during in vitro colonic fermentation. Notably, Blautia in the gut microbiota of 3-week-old mice (early life) and unclassified Lachnospiraceae in 8-week-old mice (adult life) were advantageous for transforming the pheophytins to pheophorbide a, pheophorbide b, 15¹-hydroxy-lactone pheophorbide a, and 13²-hydroxy pheophorbide a, thereby demonstrating the loss of the phytol chain in the pheophytins. Meanwhile, total short-chain fatty acids, as well as acetic, propionic, and butyric acids, were increased by the process of microbial fermentation in the presence of pheophytins. Our study provides fundamental insight into the contribution of diverse gut microbiota functions toward the biological transformation of pheophytins.