Effects of Industrial Heating Processes of Milk-Based Enteral Formulas on Site-Specific Protein Modifications and Their Relationship to in Vitro and in Vivo Protein Digestibility

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.

A comparative study on the protein digestion of four different soy beverages: effects of the composition, microstructure, and protein digestibility evaluation method

The increased consumption of soy-based products leads to the incentive for more sustainable soybean processing and more accurate nutritional evaluation. The protein structures and aggregation states of different components vary with different soy products, but their relationship with digestibility is unclear. In order to study the digestion of soy protein in complex food matrices, four soy-based beverages were carefully prepared, including whole component soy beverage (WS), soy beverage with insoluble soybean residue removed (DO-WS), soy beverage with lipids removed (DL-WS), and soy protein isolate beverage (HSPI). During digestion, the microstructure revealed that particles of all soy beverages were reduced and more evenly distributed, but striated fibres (in WS and DL-WS) still remained after digestion. Tricine-SDS-PAGE profiles showed that after in vitro gastrointestinal digestion of the four beverages, almost all the bands corresponding to the complete proteins from soy disappeared, leaving fewer visible bands with a low MW - below 12 kDa. In vitro protein digestibility analyzed by TCA precipitation (strategy B), which ranged from 64.24% to 68.70%, was more accurate, with peptides of MW <1 kDa accounting for over 84% for all the four digested fractions. Moreover, the highest values of in vitro DIAAS (96/80) and digestible protein (29.40/24.41 g per 100 g of soybeans) were achieved by WS. Characterization of the insoluble digesta further elucidated that peptides with a smaller MW (below 12 kDa) and a higher amount of hydrophobic amino acids aggregated more easily, resulting in the occurrence of precipitates and the relatively lower in vitro protein digestibility. This research contributes to the understanding of protein digestibility in whole legume-based diets, which in turn could aid in the development of new whole legume products and more efficient utilization of proteins.

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.

The influence of processing technologies on the biological activity of carbohydrates in food

Food processing transforms raw materials into different food forms using physical or chemical techniques. Recently, carbohydrates have gained attention for their diverse biological activities like antioxidant, anticancer, and antimutagenic effects. Selecting suitable processing methods is crucial to preserve the beneficial properties of carbohydrates. This review discusses the impact of non-thermal and thermal processing on the physicochemical and biological traits of carbohydrates, highlighting the need for understanding the mechanisms underlying these changes. Future research will focus on enhancing and safeguarding the biological and functional aspects of carbohydrates through improved processing techniques. The goal is to optimize methods that maintain the beneficial properties of carbohydrates, maximizing their health benefits for consumers.

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.

Infant milk formula, produced by membrane filtration, promotes mucus production in the upper small intestine of young pigs

Human breast milk promotes maturation of the infant gastrointestinal barrier, including the promotion of mucus production. In the quest to produce next generation infant milk formula (IMF), we have produced IMF by membrane filtration (MEM-IMF). With a higher quantity of native whey protein, MEM-IMF more closely mimics human breast milk than IMF produced using conventional heat treatment (HT-IMF). After a 4-week dietary intervention in young pigs, animals fed a MEM-IMF diet had a higher number of goblet cells, acidic mucus and mucin-2 in the jejunum compared to pigs fed HT-IMF (P < 0.05). In the duodenum, MEM-IMF fed pigs had increased trypsin activity in the gut lumen, increased mRNA transcript levels of claudin 1 in the mucosal scrapings and increased lactase activity in brush border membrane vesicles than those pigs fed HT-IMF (P < 0.05). In conclusion, MEM-IMF is superior to HT-IMF in the promotion of mucus production in the young gut.

Impact of process and composition of formulas for elderly on in vitro digestion using the dynamic DIDGI® model

Due to the lower efficiency of the elderly digestion system, new formulations are needed in order to increase the bioaccessibility of macronutrients. The aim of the work was to evaluate the effect of the process of protein sources production using either liquid (F2) vs spray dried milk proteins (F1/F3) and the source of lipids (vegetable oil (F1) vs mix of vegetable oil + bovine milk cream (F2/F3)) ingredients on the macronutrient digestion of three experimental elderly formulas. The dynamic in vitro digestion model DIDGI®^, was adapted to simulate the digestive conditions of the elderly. An exhaustive review of the literature was carried out in order to simulate as closely as possible the elderly digestive parameters and constituted the starting point towards a consensus in vitro digestion model that will be proposed soon by the INFOGEST scientific network. The three experimental formulas (F1/F2/F3) differing by the composition and process applied were submitted to the DIDGI® dynamic in vitro digestion over four hours using parameters adapted to the elderly. The three formulas were compared in terms of proteolysis and lipolysis. A slight impact of the process (liquid vs spray-dried) on the degree of proteolysis at the end of digestion was observed with 50.8% for F2 compared to 56.8% for F1 and 52.9% for F3 with<5% of difference between the 3 formulas. Concerning the degree of lipolysis, the addition of bovine cream led to a lesser extent of lipolysis with 63.7 and 60.2% for F2 and F3 respectively versus 66.3% for F1 (containing only vegetable oil). Our results highlighted the beneficial input of the milk fat with a higher level of phospholipids and a lower ω6/ω3 PUFA ratio and can be a good alternative to the use of the vegetable fat in drinks for elderly people.

Nutritional Evaluation of Milk-, Plant-, and Insect-Based Protein Materials by Protein Digestibility Using the INFOGEST Digestion Method

The INFOGEST method is a valuable tool for understanding and monitoring food digestion as an alternative to in vivo assays. However, few studies have compared animal and alternative protein sources in terms of protein quality using the INFOGEST method. This study aimed to evaluate the protein quality of milk-, plant-, and insect-based protein materials by in vitro protein digestibility and in vitro digestible indispensable amino acid score (DIAAS), following the INFOGEST method. Milk-based protein materials had the highest protein digestibility (86.1-90.8%), followed by soy (85.1%) and wheat (82.3%). These materials had significantly higher protein digestibility compared with zein (65.1%), cricket (63.6%), and mealworm (69.5%). Additionally, the mean values of in vitro DIAAS of milk-based protein materials (105.0-137.5) were higher than those of plant- and insect-based protein materials (1.9-91.0). Milk-based protein materials have higher protein quality than plant- and insect-based protein materials by the nutritional evaluation following the INFOGEST digestion method.

Comparison of conventional heat-treated and membrane filtered infant formula using an in vitro semi-dynamic digestion method

Introducing membrane filtration steps into infant milk formula (IMF) manufacture can partly preserve native whey proteins in the final products. In this study, IMF produced by membrane filtration (MEM-IMF) and...

Adjustment of Whey:Casein Ratio from 20:80 to 60:40 in Milk Formulation Affects Food Intake and Brainstem and Hypothalamic Neuronal Activation and Gene Expression in Laboratory Mice

Adjustment of protein content in milk formulations modifies protein and energy levels, ensures amino acid intake and affects satiety. The shift from the natural whey:casein ratio of ~20:80 in animal milk is oftentimes done to reflect the 60:40 ratio of human milk. Studies show that 20:80 versus 60:40 whey:casein milks differently affect glucose metabolism and hormone release; these data parallel animal model findings. It is unknown whether the adjustment from the 20:80 to 60:40 ratio affects appetite and brain processes related to food intake. In this set of studies, we focused on the impact of the 20:80 vs. 60:40 whey:casein content in milk on food intake and feeding-related brain processes in the adult organism. By utilising laboratory mice, we found that the 20:80 whey:casein milk formulation was consumed less avidly and was less preferred than the 60:40 formulation in short-term choice and no-choice feeding paradigms. The relative PCR analyses in the hypothalamus and brain stem revealed that the 20:80 whey:casein milk intake upregulated genes involved in early termination of feeding and in an interplay between reward and satiety, such as melanocortin 3 receptor (MC3R), oxytocin (OXT), proopiomelanocortin (POMC) and glucagon-like peptide-1 receptor (GLP1R). The 20:80 versus 60:40 whey:casein formulation intake differently affected brain neuronal activation (assessed through c-Fos, an immediate-early gene product) in the nucleus of the solitary tract, area postrema, ventromedial hypothalamic nucleus and supraoptic nucleus. We conclude that the shift from the 20:80 to 60:40 whey:casein ratio in milk affects short-term feeding and relevant brain processes.

Fermented milk retains beneficial effects on skeletal muscle protein anabolism after processing by centrifugation and supernatant removal

Lactobacillus-fermented milk can stimulate anabolic effects in skeletal muscle. Fermented milk containing Lactobacillus produces aqueous molecules, such as free AA and lactate. This study aimed to investigate how processing fermented milk by centrifugation and removal of supernatant affects AA absorption and postprandial skeletal muscle protein synthesis (MPS) when mice are fed fermented milk. We gavaged male Sprague-Dawley rats with skim milk (S), fermented milk (F), or processed fermented milk (P), and examined the total AA content in portal vein blood (reflecting AA absorption) and plantaris muscle MPS at 30, 60, and 90 min following administration. Relative to fasted rats, at 30 min the total AA concentration in portal vein blood from rats in the P groups was significantly higher, followed by F and S, respectively. The MPS rates were higher for the F or P groups compared with the S group. Phosphorylation levels of p70S6 kinase in the P and F groups were significantly higher than those for the S group 30 min after administration, although the level of Akt phosphorylation was similar among the groups. These results suggested that fermentation improves AA absorption that in turn enhances postprandial MPS via Akt-independent mechanisms, and that processed fermented milk retains these favorable effects on MPS.

Peptide Release after Simulated Infant In Vitro Digestion of Dry Heated Cow's Milk Protein and Transport of Potentially Immunoreactive Peptides across the Caco-2 Cell Monolayer

Dry heating of cow’s milk protein, as applied in the production of “baked milk”, facilitates the resolution of cow’s milk allergy symptoms upon digestion. The heating and glycation-induced changes of the protein structure can affect both digestibility and immunoreactivity. The immunological consequences may be due to changes in the peptide profile of the digested dry heated milk protein. Therefore, cow’s milk protein powder was heated at low temperature (60 °C) and high temperature (130 °C) and applied to simulated infant in vitro digestion. Digestion-derived peptides after 10 min and 60 min in the intestinal phase were measured using LC-MS/MS. Moreover, digests after 10 min intestinal digestion were applied to a Caco-2 cell monolayer. T-cell epitopes were analysed using prediction software, while specific immunoglobin E (sIgE) binding epitopes were identified based on the existing literature. The largest number of sIgE binding epitopes was found in unheated samples, while T-cell epitopes were equally represented in all samples. Transport of glycated peptide indicated a preference for glucosyl lysine and lactosyl-lysine-modified peptides, while transport of peptides containing epitope structures was limited. This showed that the release of immunoreactive peptides can be affected by the applied heating conditions; however, availability of peptides containing epitopes might be limited.

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.

Biological properties of almond proteins produced by aqueous and enzyme-assisted aqueous extraction processes from almond cake

The almond cake is a protein-rich residue generated by the mechanical expression of the almond oil. The effects of the aqueous (AEP) and enzyme-assisted aqueous extraction processes (EAEP) on the biological properties of the almond cake protein were evaluated. Total phenolic content (TPC), antioxidant capacity, inhibitory effects against crucial enzymes related to metabolic syndrome, antimicrobial potential, and in vitro protein digestibility profile were assessed. EAEP provided the best results for antioxidant capacity by both ORAC (397.2 µmol TE per g) and ABTS (650.5 µmol TE per g) methods and also showed a high (~ 98%) potential for α-glucosidase inhibition. The AEP resulted in protein extracts with the highest lipase inhibition (~ 70%) in a dose-dependent way. Enzymatic kinetic analyses revealed that EAEP generated uncompetitive inhibitors against α-glucosidase, while EAEP, AEP, and HEX-AEP (used as control) generated the same kind of inhibitors against lipase. No protein extract was effective against any of the bacteria strains tested at antimicrobial assays. An in silico theoretical hydrolysis of amandin subunits corroborated with the results found for antioxidant capacity, enzyme inhibitory experiments, and antimicrobial activity. Digestibility results indicated that the digestive proteases used were efficient in hydrolyzing almond proteins, regardless of the extraction applied and that HEX-AEP presented the highest digestibility (85%). In summary, EAEP and AEP skim proteins have the potential to be used as a nutraceutical ingredient. The biological properties observed in these extracts could help mitigate the development of metabolic syndrome where EAEP and AEP skim proteins could be potentially used as a prophylactic therapy for diabetes and obesity, respectively.

Disulfide bond formation is not crucial for the heat-induced interaction between β-lactoglobulin and milk fat globule membrane proteins

During heat treatment of milk, β-lactoglobulin (β-LG) associates with the milk fat globule membrane (MFGM). The objective of this study was to examine different binding types that could be involved in this process. First, we tested the thiol-disulfide bond interchange between β-LG and MFGM by heating raw milk (87°C, 8 min) in the presence of different reagents capable of preventing this interaction, and then evaluated the presence of β-LG in resulting MFGM preparations by sodium dodecyl sulfate-PAGE. Contrary to commonly accepted theory, β-LG still associated with MFGM when milk was heated in the presence of 10 mM N-ethylmaleimide, dithiobis-nitrobenzoic acid, or dithioerythritol. This finding indicated that noncovalent binding could be involved in the interaction, and therefore these were studied next. Preventing noncovalent interactions by heating milk in the presence of 8 M urea (to inhibit formation of hydrogen bonds) or 2 M NaCl (to inhibit electrostatic and hydrophobic interactions) reduced the association of β-LG and MFGM. Inhibiting both hydrogen and disulfide bond formation by addition of 8 M urea and 10 mM dithioerythritol or inhibiting hydrophobic interactions with 0.2% sodium dodecyl sulfate completely prevented the association. In contrast to the simple thiol-disulfide interaction model, the results suggest a more complex understanding of the interactions between β-LG and MFGM during heating of milk. This indicates that disulfide formation between β-LG and proteins in the MFGM is not required for the association, but that hydrophobic interactions and hydrogen bonding may be crucial. This novel insight into β-LG and MFGM association is in contrast to the current literature and requires further study.

How processing may affect milk protein digestion and overall physiological outcomes: A systematic review

Dairy is one of the main sources for high quality protein in the human diet. Processing may, however, cause denaturation, aggregation, and chemical modifications of its amino acids, which may impact protein quality. This systematic review covers the effect of milk protein modifications as a result of heating, on protein digestion and its physiological impact. A total of 5363 records were retrieved through the Scopus database of which a total of 102 were included. Although the degree of modification highly depends on the exact processing conditions, heating of milk proteins can modify several amino acids. In vitro and animal studies demonstrate that glycation decreases protein digestibility, and hinders amino acid availability, especially for lysine. Other chemical modifications, including oxidation, racemization, dephosphorylation and cross-linking, are less well studied, but may also impact protein digestion, which may result in decreased amino acid bioavailability and functionality. On the other hand, protein denaturation does not affect overall digestibility, but can facilitate gastric hydrolysis, especially of β-lactoglobulin. Protein denaturation can also alter gastric emptying of the protein, consequently affecting digestive kinetics that can eventually result in different post-prandial plasma amino acid appearance. Apart from processing, the kinetics of protein digestion depend on the matrix in which the protein is heated. Altogether, protein modifications may be considered indicative for processing severity. Controlling dairy processing conditions can thus be a powerful way to preserve protein quality or to steer gastrointestinal digestion kinetics and subsequent release of amino acids. Related physiological consequences mainly point towards amino acid bioavailability and immunological consequences.

Trace mineral composition of human breast milk from Brazilian mothers

BACKGROUND

Human milk is a dynamic food and some important differences in composition can be found between the milk from preterm and terms infants. Additionally, in some situations, the mother's own milk is unavailable and the use of milk from human milk banks is considered as the most appropriate substitute. In this way, concentrations of trace elements (Ba, Cu, Fe, Mn, Mo, Se, Sr, and Zn) were determined in human milk, considering the differences about preterm and term human milk and its processing in a human milk bank.

METHODS

A total of 156 samples were analyzed, which were divided in three groups: samples collected at the hospital at bedside (BS, 60 samples) from mothers of preterm infants and samples from mothers of term infants collected in a human milk bank without pasteurization (WP, 49 samples) and pasteurized by the Holder procedure (P, 47 samples). The analyzes were conducted by inductively coupled plasma mass spectrometry (ICP-MS) after the treatment of the samples with acid mineralization assisted by microwave radiation.

RESULTS

Concentrations varied in a range of 0.6-88.2 μg/L for Ba, 78.6-954.5 μg/L for Cu, 24.2-5229.2 μg/L for Fe, 0.4-42.6 μg/L for Mn, 0.1-39.1 μg/L for Mo, 2.5-70.6 μg/L for Se, 8.9-187.5 μg/L for Sr and 76.3-17727.2 μg/L for Zn. Significant differences (p < 0.05) were found between preterm (BS) and term human milk (WP and P) for Ba, Cu, Mo, Se, and Zn, whereas the processing of the donated milk by Holder pasteurization did not influence the concentration of the studied trace elements. The milk of term infants does not attend the recommended daily intake (RDI) of Zn and for preterm infants the RDI of Fe and Mn is not achieved.

CONCLUSIONS

The higher concentrations of Cu, Mo, Se and Zn observed in milk from mothers of preterm infants indicate that the milk to be offered for these high-risk neonates in neonatal intensive care units should contain higher levels of these trace elements. Besides, considering the RDI, the milk of term infants should be fortified with Zn, whereas the milk of preterm infants should be fortified with Fe.

Casein materials show different digestion patterns using an in vitro gastrointestinal model and different release of glucagon-like peptide-1 by enteroendocrine GLUTag cells

Physicochemical properties of casein (CN) materials manufactured using different processes are well studied; however, data on their bioaccessibility or bioactivity are limited. We compared the digestion patterns and glucagon-like peptide-1 (GLP-1)-releasing activities of micellar CN concentrate (MCC) and sodium caseinate (SCN). MCC and SCN mixed with whey protein isolate (SCN + WPI) were subjected to in vitro gastrointestinal digestion; the digestibility of MCC was higher than that of SCN + WPI, and both CN materials showed different patterns of peptides released after in vitro digestion. A comparison of GLP-1-releasing activities showed that MCC induced GLP-1 secretion to a greater extent than SCN + WPI. Candidate peptides identified from CN digesta were chemically synthesized to test their GLP-1-releasing activity. GPVRGPFPIIV identified only in the MCC digesta, could stimulate GLP-1 release. In conclusion, the digestion patterns and GLP-1-releasing activity of CN materials depend on the production process.

Human milk peptides differentiate between the preterm and term infant and across varying lactational stages

Variations in endogenous peptide profiles, functionality, and the enzymes responsible for the formation of these peptides in human milk are understudied. Additionally, there is a lack of knowledge regarding peptides in donor human milk, which is used to feed preterm infants when mother's own milk is not (sufficiently) available. To assess this, 29 human milk samples from the Dutch Human Milk Bank were analyzed as three groups, preterm late lactation stage (LS) (n = 12), term early (n = 8) and term late LS (n = 9). Gestational age (GA) groups were defined as preterm (24-36 weeks) and term (≥37 weeks). LS was determined as days postpartum as early (16-36 days) or late (55-88 days). Peptides, analyzed by LC-MS/MS, and parent proteins (proteins from matched peptide sequences) were identified and quantified, after which peptide functionality and the enzymes responsible for protein cleavage were determined. A total of 16 different parent proteins were identified from human milk, with no differences by GA or LS. We identified 1104 endogenous peptides, of which, the majority were from the parent proteins β-casein, polymeric immunoglobulin receptor, α_s1-casein, osteopontin, and κ-casein. The absolute number of peptides differed by GA and LS with 30 and 41 differing sequences respectively (p < 0.05) Odds likelihood tests determined that 32 peptides had a predicted bioactive functionality, with no significant differences between groups. Enzyme prediction analysis showed that plasmin/trypsin enzymes most likely cleaved the identified human milk peptides. These results explain some of the variation in endogenous peptides in human milk, leading to future targets that may be studied for functionality.

Alcalase Enzymolysis of Red Bean (adzuki) Ferritin Achieves Nanoencapsulation of Food Nutrients in a Mild Condition

Classical methods to fabricate ferritin-nutrients shell-core nanoparticles usually apply extremely acid/alkaline pH transition, which may cause the activity loss of nutrients or the formation of insoluble aggregates. In this work, we prepared an extension peptide (EP) deleted red bean (adzuki) ferritin (apoRBFΔEP) by Alcalase 3.0T enzymolysis. Such enzymolysis could delete the EP domain and remain the typical shell-like structure of the ferritin. Meanwhile, the α-helix content of apoRBFΔEP was decreased by 5.5%, and the transition temperature (T_m) was decreased by 4.1 °C. Interestingly, the apoRBFΔEP can be disassembled into subunits under a benign condition at pH 4.0 and is assembled to form an intact cage protein when the pH was increased to 6.7. By using this novel route, the epigallocatechin gallate (EGCG) molecules were successfully encapsulated into the apoRBFΔEP cage with an encapsulation ratio of 11.6% (w/w), which was comparable with that by the traditional pH 2.0 transition. The newly prepared EGCG-loaded apoRBFΔEP exhibited a similarly protective effect on the EGCG upon simulated gastrointestinal tract and thermal treatment as compared with the control. In addition, the EGCG-loaded apoRBFΔEP could significantly relieve the ferritin association induced by pH transition, which was superior to traditional method. The thinking of this work will be especially suitable for encapsulating pH-sensitive molecules based on ferritin in a benign condition.

Heat-induced inactivation mechanism of soybean Bowman-Birk inhibitors

Due to the complications of the soymilk system, the heat-induced Bowman-Birk inhibitor (BBI) inactivation mechanism is not well known. In this study, two BBI samples with low and high purities were prepared from soymilk. It was confirmed that three groups (A, C, and D) of BBI, which are contained in soybean seeds, were transferred into soymilk during processing. On heating, it was found that 1) the two subdomains of BBI were not equally heat stable, 2) the conformation of BBI gradually changed, 3) some amino acid residues (namely, cystine, serine and lysine) in BBI were degraded, 4) BBI did not tend to form intermolecular cross-links with another BBI, but did slightly with non-BBI proteins. Based on some previous studies, the conformational change of BBI was attributed to β-elimination reactions on the amino acid residues of BBI and the subsequent intramolecular reactions induced by the products yielded by the β-elimination reactions.

Urea-Driven Epigallocatechin Gallate (EGCG) Permeation into the Ferritin Cage, an Innovative Method for Fabrication of Protein-Polyphenol Co-assemblies

The 8 nm diameter cavity endows the ferritin cage with a natural space to encapsulate food components. In this work, urea was explored as a novel medium to facilitate the formation of ferritin-polyphenol co-assemblies. Results indicated that urea (20 mM) could expand the 4-fold channel size of apo-red bean ferritin (apoRBF) with an increased initial iron release rate υ₀ (0.22 ± 0.02 μM min^-1) and decreased α-helix content (5.6%). Moreover, urea (20 mM) could facilitate the permeation of EGCG into the apoRBF without destroying the ferritin structure and thus form ferritin-EGCG co-assemblies (FECs) with an encapsulation ratio and loading capacity of 17.6 and 2.1% (w/w), respectively. TEM exhibited that FECs maintained a spherical morphology with a 12 nm diameter in size. Fluorescence analysis showed that urea intervention could improve the binding constant K [(1.22 ± 0.8) × 10⁴ M^-1] of EGCG to apoRBF. Furthermore, the EGCG thermal stability was significantly improved (20-60 °C) compared with free EGCG. Additionally, this urea-involved method was applicable for chlorogenic acid and anthocyanin encapsulation by the apoRBF cage. Thus, urea shows potential as a novel potential medium to encapsulate and stabilize bioactive polyphenols for food usage based on the ferritin protein cage structure.

Bioactive peptides released by in vitro digestion of standard and hydrolyzed infant formulas

Hydrolyzed infant formulas serve as appropriate nutritional sources for infants afflicted with cow's milk allergy, and milk proteins in hydrolyzed formulas are industrially hydrolyzed extensively or partially. To investigate whether industrial hydrolysis may modulate the digestive trajectory of milk proteins, thereby releasing different profiles of bioactive peptides compared with standard formulas, both standard and hydrolyzed formulas were subjected to in vitro digestion and formation of bioactive peptides were compared. One standard, one extensively hydrolyzed, and one partially hydrolyzed infant formula were digested in vitro with pepsin and pancreatin, taking into account the higher gastric pH of infants, and the digesta were subjected to peptidomic analysis. The standard formula released a larger variety of bioactive peptides than from the hydrolyzed formulas, indicating that industrial hydrolysis of milk proteins may generally attenuate their indigenous bioactivities such as antibacterial, immuno-regulatory, and anti-oxidative activities. Conversely, industrial hydrolysis may facilitate the formation of bioactive peptides from hydrophobic proteins/regions such as β-LG and the "strategic zone" of β-CN, which encrypt bioactive peptides including a dipeptidyl dipeptidase-4-inhibitory, hypocholesterolemic, and opioid peptides. Infants fed hydrolyzed infant formulas may be influenced by milk protein-derived bioactive peptides in a manner different from those fed standard formula.