Model Infant Formula Research Articles

Storage stability of model infant formula powders produced under varying wet-mix processing conditions

Wet-mixing processes can be tuned to reduce energy consumption, although impacts on quality and stability should be addressed. This work evaluated the effect of wet-mix processing (total solids, TS: 50 or 60%; heat treatment: 75 or 100 °C × 18 s) and storage conditions (open package: 25 °C, 58% RH, 4 weeks; closed package: 25 °C, multilayer bag, 12 weeks) on the physicochemical stability and digestibility of infant formulas. Processing significantly influenced the physicochemical characteristics of the powders, with TS exerting a stronger impact than heat treatment. Powders produced from 60% TS wet mixes presented the fastest water sorption, which accelerated lactose crystallisation and fat liberation. Formulas in closed packages were stable for 12 weeks. While lactose crystallised before week 2 in open-package storage, inducing major physical changes, only limited effects were observed on digestibility. These findings provide valuable insights to ensure consistent quality during shelf-life of infant formula.

Simulated in vitro infant digestion and lipidomic analysis to explore how the milk fat globule membrane modulates fat digestion

We hypothesized that the addition of milk fat globule membranes (MFGMs) to infant formula would improve its lipolysis, making it more similar to human milk (HM) and superior to commercial infant formula (CIF) in fat digestion. Therefore, we prepared two model infant formulas (MIFs) by adding MFGMs to dairy ingredients in different ways and compared their fat digestion behavior with those of HM and CIF. MFGMs were added alone (MIF1) and with other milk-based materials (MIF2) before homogenization. The addition of MFGMs reduced the flocculation of lipids and proteins in the gastric phase and promoted lipolysis in the intestine phase. The amount of free fatty acids released followed the order of HM > MIF1 > CIF ≥ MIF2. After digestion, the number of different glyceride species between each sample and HM reached 64 (MIF1), 73 (MIF2), 67 (CIF1), and 72 (CIF2). In conclusion, the fat digestion of MIF1 had the highest similarity with HM.

Application of a whey protein ingredient for simultaneous co-enrichment of infant formula with α-lactalbumin and milk fat globule membrane

α-Lactalbumin (α-lac) and milk fat globule membrane (MFGM) are bioactive components of human milk beneficial for infant health and development. The strategic design of high-quality dairy ingredients, to include bioactive components such as α-lac and MFGM can contribute to the continued scientific advancement of infant formula (IF). It was demonstrated in this study that a unique whey protein ingredient could be used to achieve co-enrichment of IF with α-lac and MFGM. Model IF containing alternative whey ingredients specifically enriched in either α-lac or MFGM were also designed for comparison. A further finding was that the magnitude of IF MFGM enrichment could not be confirmed using microscopy alone and so, quantitative compositional analysis was required. This research demonstrated that the bioactive profile of an IF could be enhanced by selecting a unique whey protein ingredient co-enriched in α-lac and MFGM during formulation.

Regulating the lipid droplet interface based on milk fat globule membrane and milk proteins to improve lipid digestion of model infant formula emulsion

The interfacial properties of lipid droplets play a crucial role in lipid digestion. In this study, milk fat globule membrane (MFGM) was used to improve the lipid droplet interface of model infant formula emulsions (IFEs). We focused on the effects of the addition sequence of MFGM and milk proteins commonly used in infant formula (IFE1: Milk proteins added before homogenization, MFGM added after homogenization; IFE2: MFGM added before homogenization, milk proteins added after homogenization; IFE3: MFGM and milk proteins added before homogenization) on lipid droplets' interfacial compositions, structure, and lipid digestion behaviors and compared with human milk (HM) and commercial infant formula (IF). The results showed that the interfacial protein load was significantly lower (P < 0.05), and the interfacial phospholipid load was significantly higher (P < 0.05) in IFE2 compared to IFE1, IFE3, and IF. The lipid droplet structure of IFE2 is closer to that of HM. MFGM fragments-covered lipid droplets can be observed in IFE2. In contrast, the lipid droplets in IFE1, IFE3, and IF were covered by casein micelles, and MFGM fragments were free in the serum phase. After digestion, the lipolysis degree of IFE2 (91.7 ± 1.51%) was comparable to that of HM (94.98 ± 1.08%) and significantly higher than other samples (P < 0.05). During digestion, IFE1 and IFE3 formed thicker and denser protein knit networks compared to IFE2. The lipid droplets in IFE1 and IFE3 were embedded in protein networks, thereby inhibiting lipid digestion. These results indicated that changes in the interfacial composition of lipid droplets improved lipid digestion by mitigating the aggregate and coalescence of protein and lipid droplets.

Effect of phospholipid matrix on emulsion stability, microstructure, proteolysis, and in vitro digestibility in model infant formula emulsion

The effects of adding different phospholipid (PL) matrices [milk sphingomyelin (SM) vs soy phosphatidylcholine (PC)] on emulsion stability, microstructure, and in vitro simulated lipid digestion were examined using a Model Infant Formula Emulsion (MIFE). The emulsion stability of MIFE increased significantly with PL addition (0.1 and 0.2 %). Compared to sole MIFE or MIFE + PC, the incorporation of SM resulted in increased emulsion stability (p < 0.05) and a greater amount of free fatty acid release (p < 0.05) during in vitro simulated digestion. This was mainly due to the reduction of intensive droplet aggregation, thus providing a large surface area and improved digestibility. This is further experimentally supported by the evolution of particle size distribution, zeta-potential, and microstructure analysis using confocal laser scanning microscopy. The incorporation of SM in the emulsion formation significantly delayed digestion of β-lactoglobulin during in vitro digestion. Lipid digestibility in MIFE was altered depending on the type of PL matrix, and SM displayed a superior effect to PC. Thus, the creation of a novel emulsion interface by the appropriate selection of emulsifiers can be used to improve lipid digestion in infants and obtain desirable nutritional consequences.

Effect of casein-whey ingredient blends on the protein stability of model infant formulas

Milk protein concentrate (MPC 80), skim milk powder, acid whey protein concentrate (aWPC 35), cheese whey protein concentrate and isolate (cWPC 35 and cWPI) were assessed for suitability in infant formula (IF) applications with total solids similar to commercial ready-to-drink applications. Serum-phase compounds including phosphate, citrate and chloride in casein-rich streams, especially aWPC 35, played an important role in controlling whey protein thermal aggregation. Replacing cWPC 35 with cWPI improved protein stability at UHT temperatures, indicating that removal of minerals from whey protein streams could increase thermal stability of formulations. At HTST temperatures (95 °C), lactose appeared to have a protective effect against protein denaturation. At 140 °C, however, lactose contributed to cascading Maillard reactions triggering complete protein destabilisation; this occurred most rapidly in MPC 80 formulations that were comparatively low in serum-phase calcium-binding species (phosphate and citrate). These findings highlight how innate minerals and lactose impact protein stability during IF manufacture.

Model infant formulas: Influence of types of whey proteins and lipid composition on the in vitro static digestion behavior

This work aimed at evaluating the influence of types of whey proteins (lactoferrin, whey protein isolate and/or whey protein hydrolysates) and lipid composition (high oleic sunflower oil, coconut oil and/or medium chain triacylglycerols) on the behavior of model infant formulas (IFs) under simulated conditions of the infant gastrointestinal tract using an in vitro static digestion model. The physicochemical conditions of the gastric medium resulted in the aggregation of oil the droplets and partial hydrolysis of the proteins, considering whey proteins were resistant to the gastric conditions. However, after intestinal digestion the proteins from all the IFs were extensively hydrolyzed. The lipid composition of the IFs did not influence the protein hydrolysis, but the protein composition of the IFs altered the release of free fatty acids. The presence of lactoferrin in the IFs resulted in a higher free fatty acids release compared to IFs of same lipid composition. In terms of lipid composition, IFs containing coconut oil and medium chain triacylglycerols showed extremely higher free fatty acids release than those containing only long chain triacylglycerols. These results are promising for the design of infant foods containing fast-absorbing functional ingredients.

Breakage behaviour and functionality of spray-dried agglomerated model infant milk formula: Effect of proteins and carbohydrates content

This study explored the effect of protein content (whey protein and casein) and carbohydrate content (lactose, sucrose, and maltodextrin) on the breakage behaviour and its influence on spray-dried agglomerated model infant milk formula. Whey protein powders were bigger in particle size, weaker in structural strength, and marginally more irregular in shape, which resulted in better rehydration properties but more breakage than pure casein powders. Similarly, sucrose samples had better rehydration properties and higher glass transition temperatures but suffered more breakage than maltodextrin and pure lactose powders because of their bigger particle size. The influence of proteins on breakage was greater than that of carbohydrates. Breakage changed the physical and structural properties of powders, especially for whey protein and sucrose samples, which caused the deterioration of rehydration properties and the decrease in crystallization temperatures. From the perspective of particle breakage, unwanted dairy powder breakage could be controlled by changing powder formulations.

Probing the cumulative effects of unit operations and lactose to whey protein ratios on protein modifications in powdered model infant formula

The impact of lactose to whey protein ratio on processed-induced protein modifications was investigated in powdered model infant formula. Model samples were prepared with different lactose to whey protein ratios and different total protein concentrations; protein modifications were evaluated before, during and after processing. Lab-scale equipment was used to mimic commercial manufacturing, and a powdered young-child formula was included to elucidate cumulative effects of commercial unit operations. Maillard-related and structural protein modifications were affected differently by unit operations, both in model samples and commercial formula. Maillard reaction products (furosine, α-dicarbonyls and advanced glycation end products) increased with increased lactose content of model samples, whereas absence of lactose facilitated formation of disulphide-linked aggregates, lysinoalanine and lanthionine. The lowest level of protein modifications was observed at a 30:70 lactose to whey protein ratio, suggesting partial dry blending of lactose as a feasible approach to improve protein quality in powdered infant formula.

Protein structure in model infant milk formulas impacts their kinetics of hydrolysis under in vitro dynamic digestion

The impact of protein structure in model infant milk formulas (IMFs) on digestion was evaluated using an in vitro dynamic digestion model. IMFs differed by their whey protein profile and the heating conditions. Digesta microstructure was followed by laser light scattering and confocal laser scanning microscopy. Proteolysis kinetics were monitored by SDS-PAGE and OPA assay and peptide release kinetics by tandem mass spectrometry. The gastric digesta microstructure depended on the protein structure within IMFs, with the highest protein particle size in IMF containing native casein micelles. Among whey proteins, denatured/aggregated lactoferrin was the most sensitive to pepsin hydrolysis. The peptidomic profile during digestion varied among IMFs. More numerous and resistant intestinal bioactive peptides were observed for the unheated IMF having a whey protein profile closer to that of human milk. Further physiological studies are required to investigate the benefits of adapting the IMF whey protein profile on infant health.

Influence of low molecular weight surfactants on the stability of model infant formula emulsions based on hydrolyzed rice protein

The emulsifying properties of rice protein ingredients, and their behaviour in the presence of other non-protein emulsifiers, are essential to support food applications. The objective of this study was to investigate the influence of different low molecular weight surfactants (LMWS) on the stability of model infant formula emulsions (10 g protein L−1, 35 g soybean oil L−1, 50 g carbohydrate L−1) based on a rice protein hydrolyzate (RPH). Inclusion of CITREM and DATEM, at concentrations greater than 1 g L−1, gave emulsions with mean fat globule diameters (D[4,3]) less than 1 μm with good creaming stability, while lecithin was less effective across the concentration range tested (i.e., 1–3 g L−1). Coalescence of the control emulsion was observed upon both storage (10 d at 4 °C) and heat treatment (95 °C × 5 min). Increasing CITREM concentration increased storage and heat stability of the emulsions, while addition of CITREM at 2 g L−1 facilitated the formation of a very stable product. This study provides a first insight into the potential of hydrolyzed rice protein to be used as a value-added ingredient in the production of nutritional beverages such as infant formula emulsions, and the influence of LMWS on the stability of such products.

Influence of protein content and profile on the processing characteristics and physical properties of model infant formula powders

Formulas were designed and produced with protein contents of 10, 14 and 18 g/100 g and whey protein:casein ratios of 60:40, 40:60 and 20:80. Protein content and whey protein:casein ratio did not significantly affect the volume mean diameter (D[4,3]) of milk fat globules during processing; however, increasing protein content and decreasing whey protein:casein ratio resulted in increased viscosity during processing. The free fat content of the powders decreased with increasing protein content. Particle and bulk densities of powders with whey protein:casein ratio of 20:80 were higher than that of powders with whey protein:casein ratio of 60:40.

Impact of wet-mix total solids content and heat treatment on physicochemical and techno-functional properties of infant milk formula powders

This paper investigated the effects of heat treatment (75 °C × 18 s and 100 °C × 18 s) and wet-mix total solids level (TS: 50 and 60%, w/w) on the physicochemical and techno-functional properties of model infant milk formula (IMF) powders. IMF produced from wet-mixes with 50% TS preheated at 75 °C (50%-75°C) exhibited the longest wettability time (55 ± 2 s) and the poorest flowability, explained by the small particle size (D [4;3]= 16.5 ± 2.29 μm) and low poured bulk density (0.27 ± 0.02 g/cm3). Larger particles were obtained by increasing both pasteurization temperature and TS. Further, powders from 60% TS wet-mixes showed less particle size uniformity, leading to better packing and higher bulk densities. 50%-75°C powders also showed the lowest onset glass transition temperature, which may affect its storage stability. Wettability time was reduced by increasing TS from 50 to 60% or by increasing pre-heating temperature from 75 to 100 °C. However, as observed by low-field nuclear magnetic resonance, the increase in the pasteurization temperature slowed down the global rehydration process. The flowing properties of the powders improved by increasing TS level of the wet-mix. In conclusion, the pre-spray drying wet-mix processing variables, pasteurization temperature and TS level, had a major effect on the physicochemical and functional properties of the IMF powders. It is crucial to understand how variations in the process parameters affect these powder characteristics, due to their functional, technological and economic importance.

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

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. 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 (31.9μm), 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 (17.8μm) 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. 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.

Calcium fortification of a model infant milk formula system using soluble and insoluble calcium salts

The impact of calcium fortification, delivered using different proportions of soluble (calcium chloride; CaCl2) and insoluble (micronised calcium citrate; CaCit) calcium salts, on physicochemical and thermal stability properties of a model infant milk formula (IMF) was determined. The IMF was formulated with a whey protein fraction dominant in α-lactalbumin and fortified with calcium (1500 mg L−1) using 70:30, 60:40, 50:50, 40:60 and 30:70 ratios of CaCit:CaCl2. Increasing CaCl2 levels decreased the net zeta-potential of IMFs from −41.0 to −22.1 mV and increased ionic calcium levels (1.44–6.99 mm). The apparent viscosity, especially at acidic pH (6.40), increased compared to the control with values ranging from 22.3 to 50.2 mPa s for ratios 70:30 and 30:70, respectively. In addition, mean particle size of the IMF increased, with values ranging from 2.19 to 43.4 μm. This study provides useful information in supporting next-generation fortification strategies of nutritional dairy-based products with calcium.

Model infant formulas: Influence of types of whey proteins and oil composition on emulsion and powder properties

This study aimed at producing model infant formulas using different types of proteins (lactoferrin, whey protein isolate and/or whey protein hydrolysate) and oils (high oleic sunflower oil, coconut oil and/or caprylic/capric triglyceride mixture) in order to evaluate the influence of the interactions among the ingredients on the structural characteristics of the emulsions and the powders. Lactoferrin showed to be a promising ingredient for incorporation into infant formulas, allowing its association with whey protein hydrolysates to maintain the stability of the emulsion. In addition, model infant formula powders containing lactoferrin resulted in powders with higher values of yield (52.0–74.3%), encapsulation efficiency (90.8–97.2%) and hygroscopicity (11.7–13.4%) and better wettability. The oil blends containing medium chain triacylglycerols also showed adequacy to produce stable emulsions with reduced droplet size (1.31 μm) and powders with bigger encapsulation efficiency (97.2%). This study concludes that the great protein-protein interaction, as well as the different types of oil, influenced on the powder characteristics and the drying performance.

Infant milk formulae processing: Effect of wet-mix total solids and heat treatment temperature on rheological, emulsifying and nutritional properties

This study investigated the effects of total solids (TS) in the wet-mix and pasteurisation temperature on the whey protein (WP) denaturation, rheological behaviour, emulsifying properties and available lysine content of a model infant milk formula (IMF). IMF with 50% or 60% (w/w) TS were produced by wet-mix process and pasteurised at 75 °C or 100 °C for 18 s. Measurements were taken after dispersion, pasteurisation, homogenisation and spray-drying of wet-mix. Pasteurisation at 100 °C caused extensive WP denaturation (above 80%) and increased the viscosity. Available lysine content was 52% higher in powdered IMF obtained from wet-mixes pasteurised at 75 °C compared to 100 °C. A significant reduction in energy consumption could be achieved by producing IMF from 60% TS wet-mixes pasteurised at 75 °C, while obtaining powders with less than 7% WP denaturation, no loss of available lysine during processing and post-reconstitution stability for 2 h.

Changes in physicochemical and surface characteristics in model infant milk formula powder (IMF) during storage

Shelf life of infant milk formula (IMF) powders depends on product composition and storage environment. We produced model IMF powders by mimicking human milk and investigated the effects of storage conditions on surface characteristics and caking behavior of these powders. The powders were stored for 21 days at two different temperatures (25 °C and 45 °C) and three relative humidity (RH) levels (11%, 44%, and 85%). The storage of these powders at higher RH, higher temperature, or their combinations increased lactose crystallinity, increased surface fat content, altered surface chemical composition, and induced caking. The powders stored at 45 °C and 85% RH had highest lactose crystallinity and fat content on the surface. The increase in crystallinity and surface free fat also increased the caking strength. Storage at ambient temperature (25 °C) and low RH levels (11% and 44%) was found to avoid lactose crystallization and caking. These findings will help manufacturers and consumers to implement suitable storage protocols that would help extend shelf life of IMF powders.

Structural characterization of heat-induced protein aggregates in model infant milk formulas

Heat treatments induce structural modifications of bovine milk proteins. In this study, we aimed to investigate how these structural modifications are affected by the whey protein profile of infant milk formulas (IMFs) and heat treatment parameters. Three model IMFs (1.3% of proteins; casein:whey protein ratio 40:60) differing by the whey protein profile (1:3.37 α-lactalbumin (α-LA):β-lactoglobulin (β-LG), 1:3.26:1.80 α-LA:β-LG:lactoferrin (LF) or 1:0.13:0.40 α-LA:β-LG:LF), were heated at 67.5 °C or 80 °C to reach an akin whey protein denaturation extent of 65%. Protein structures were analyzed by asymmetrical flow field-flow fractionation coupled with multiangle light scattering and differential refractometer, transmission electron microscopy and electrophoresis. The unheated IMFs were used as reference. The results showed that LF addition in IMFs induced partial casein micelle disintegration before heating. In the absence of added LF, the heat-denatured whey proteins either formed soluble whey protein aggregates or casein micelle-bound whey protein aggregates. The latter were favored at the expense of soluble aggregates in the heated IMFs with the LF content increase and the concomitant β-LG content decrease. Consequently, the casein micelle structure was strongly dependent on the β-LG and LF amounts in IMFs and on the heating temperature. In the IMFs containing β-LG and LF and at temperature greater than the β-LG denaturation temperature, the casein micelles exhibited filamentous appendages on its surface after heating. Below the denaturation temperature of β-LG and in IMFs containing trace β-LG amount, the heated casein micelles were perfectly spherical with a smooth surface.

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

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