Dynamic gastric stability and in vitro lipid digestion of whey-protein-stabilised emulsions: Effect of heat treatment

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.

Enhancing lipid digestion and absorption rate: The role of whey protein isolate short fibrils in emulsions

Lipid serve as a crucial energy source during prolonged endurance exercise, and whey protein isolate (WPI) is commonly applied in food emulsions to modulate lipid digestibility. Herein, we prepared WPI short fibrils, <400 nm in length, to stabilize emulsion and increase lipid digestion and absorption rates. Specifically, a 2 % (w/v) WPI solution was adjusted to pH 2 and heated at 90 °C for 6 h to produce long fibrils, followed by 168 h of shear force treatment to obtain short fibrils. Compared to native WPI and long fibrils, short fibrils exhibited smaller molecular weight and higher surface hydrophobicity. Both short and long fibrils showed no cytotoxic effects on BRL and HEK-293 cells. Emulsions stabilized by short fibrils displayed excellent emulsifying capacity and stability, along with favorable dispersion during in vitro digestion. Importantly, the short fibrils emulsion improved in vitro digestion rate of lipids and promoted the rapid lipid absorption in vivo. These findings suggest that modifying protein fibrils around oil droplets can modulate lipid digestibility, with short fibrils offering potential to improve lipid absorption in functional foods tailored for personalized nutrition in extreme endurance exercise.

Combining heat treatment and conjugation between guarana extract and pea protein isolate to produce O/W emulsions loaded with vitamin D3

Growing interest in plant-based materials for stabilizing food emulsions is driven by the clean-label trend. Conjugating plant proteins with phenolic compounds from plant extracts enhances their techno-functionality and allows their use as stabilizers of emulsion-based systems. This study aimed to (i) combine heat treatment (HT) and conjugation with guarana extract (GE) to improve the emulsifying ability of pea protein isolate (PPI); (ii) encapsulate vitamin D3 (VD) in PPI/GE-stabilized emulsions; (iii) evaluate the potential of these formulations in improving VD retention during storage and in vitro bioaccessibility. The particles showed a size distribution ranging from 0.5 to 10 µm, depending on the processing sequence. Furthermore, HT on PPI dispersions followed by conjugation with GE led to microgels that stabilized emulsions during 30 days of storage at 25 °C. Also, the conjugates significantly improved VD retention, ranging from 74 to 100 %, after 30 days of storage at 25 °C, even in the presence of UV light. VD-loaded emulsions produced by PPI-GE conjugates showed higher bioaccessibility values (>65 %) compared to emulsions produced by PPI alone (∼58 %) and VD-incorporated sunflower oil (37 %). Given the above, the technological modification of PPI through conjugation with GE phenolic compounds and HT efficiently produced O/W emulsions loaded with VD, improving its bioaccessibility and tailoring a system with potential application in plant-based beverage and dessert formulations.

Effect of different pretreatment methods on the stability of pumpkin seed milk and potential mechanism

Pumpkin seeds represent a valuable source of plant protein and can be utilized in the production of plant-based milks. This study aims to investigate the effects of different pretreatment techniques on the stability of Pumpkin Seed Milk (PSM) and explore potential mechanisms. Raw pumpkin seeds underwent pretreatment through roasting, microwaving, and steaming to prepare PSM. Physiochemical attributes such as composition, storage stability, and particle size of PSM were evaluated. Results indicate that stability significantly improved at roasting temperatures of 160 °C, with the smallest particle size (305 ± 40 nm) and highest stability coefficient (0.710 ± 0.002) observed. Nutrient content in PSM remained largely unaffected at 160 °C. Protein oxidation levels, infrared, and fluorescence spectra analysis revealed that higher temperatures exacerbated the oxidation of pumpkin seed emulsion. Overall, roasting raw pumpkin seeds at 160 °C is suggested to enhance PSM quality while preserving nutrient content.

Dynamic In Vitro Gastric Digestion Behaviour of Commercial Infant Formulae Made with Cow, Goat and Sheep Milk

There are a wide range of commercial infant formulae available on the market. These are made using milk from different species, such as goat, sheep, and cow. The different protein compositions of these milks and the process used during infant-formulae manufacture, such as heat treatment, may impact the digestion of nutrients. This study compared the effect of protein composition and heat treatment on the in vitro gastric digestion behaviour of commercial infant formulae made with cow, goat, and sheep milk using a dynamic infant human gastric simulator (IHGS). During the simulated dynamic gastric digestion, the goat milk infant formula (GIF) showed earlier signs of aggregate formation compared to cow milk infant formula (CIF) and sheep milk infant formula (SIF). In addition, the microstructures of GIF chyme showed fragmented and porous structures. On the contrary, CIF formed dense protein networks that trapped oil droplets, whereas SIF exhibited a microstructure of smooth oil droplets surrounded by fewer protein networks. The different aggregation behaviours and aggregate structures of the three infant-formulae chyme were related to their different protein compositions, especially the different casein compositions. Furthermore, the open fragile structure of GIF aggregates provided easier access to pepsin, allowing it to hydrolyse protein. The results from the present study provided some information to assist in understanding the coagulation and digestion behaviours of commercial infant formulae made from different species of milk.

Noncovalent interactions between biomolecules facilitated their application in food emulsions' construction: A review

The use of biomolecules, such as proteins, polysaccharides, saponins, and phospholipids, instead of synthetic emulsifiers in food emulsion creation has generated significant interest among food scientists due to their advantages of being nontoxic, harmless, edible, and biocompatible. However, using a single biomolecule may not always meet practical needs for food emulsion applications. Therefore, biomolecules often require modification to achieve ideal interfacial properties. Among them, noncovalent interactions between biomolecules represent a promising physical modification method to modulate their interfacial properties without causing the health risks associated with forming new chemical bonds. Electrostatic interactions, hydrophobic interactions, and hydrogen bonding are examples of noncovalent interactions that facilitate biomolecules' effective applications in food emulsions. These interactions positively impact the physical stability, oxidative stability, digestibility, delivery characteristics, response sensitivity, and printability of biomolecule-based food emulsions. Nevertheless, using noncovalent interactions between biomolecules to facilitate their application in food emulsions still has limitations that need further improvement. This review introduced common biomolecule emulsifiers, the promotion effect of noncovalent interactions between biomolecules on the construction of emulsions with different biomolecules, their positive impact on the performance of emulsions, as well as their limitations and prospects in the construction of biomolecule-based emulsions. In conclusion, the future design and development of food emulsions will increasingly rely on noncovalent interactions between biomolecules. However, further improvements are necessary to fully exploit these interactions for constructing biomolecule-based emulsions.

Curcumin-loaded oil body emulsions prepared by an ultrasonic and pH-driven method: Fundamental properties, stability, and digestion characteristics

In this study, oil bodies (OBs) loaded with curcumin (Cur) were successfully prepared via an ultrasonic and pH-driven method. Ultrasonic treatment significantly improved the encapsulation efficiency (EE) and loading capacity (LC) of Cur, producing OB particles with small size, uniform distribution, and high ζ-potential absolute values. When the ultrasonic power was 200 W, the EE, LC, and ζ-potential absolute value were the greatest (88.27 %, 0.044 %, and -25.71 mV, respectively), and the OBs possessed the highest yellowness, representing the best treatment result. The confocal laser scanning microscopy (CLSM) and cryo-scanning electron microscopy (cryo-SEM) results was also intuitionally shown that. Moreover, circular dichroism (CD) proved that ultrasonic treatment could unfold the surface protein structure, further enhancing the stability. Therefore, the cream index (CI), peroxide value (POV), and thiobarbituric acid reactive substances (TBARS) were the lowest when the ultrasonic power was 200 W. In this case, the Cur loaded in OBs was well protected against hostile conditions, evidenced by the highest Cur retention rate and the lowest degradation rate constant. Finally, the in vitro gastrointestinal digestion simulation results showed that the ultrasonic treatment effectively increased the release of FFA, bioaccessibility, and stability of Cur, especially when the ultrasonic power was 200 W. This research offers a new OB-based delivery system to stabilize, deliver, and protect Cur for food processing.

Effect of Heat Treatment on the Digestive Characteristics of Different Soybean Oil Body Emulsions

Soybean oil body (SOB) emulsions were prepared using OBs extracted at pH 11.0 and pH 7.0. The pH 11.0-SOB comprised oleosins, whereas pH 7.0-SOB comprised extrinsic proteins and oleosins. All SOB emulsions were heated at 60-100 °C for 15 min. Heating may lead to the release of extrinsic proteins from the surface of pH 7.0-SOB due to heat-induced denaturation. The total proportion of α-helix and β-sheets gradually decreased from 77 (unheated) to 36.2% (100 °C). During stomach digestion, the extrinsic protein hydrolysis of heated pH 7.0-SOB emulsions was fast between 60 and 80 °C, and it then slowed between 90 and 100 °C; heating inhibited the oleosin hydrolysis of pH 7.0- and 11.0-SOBs. Heat treatment promoted aggregation and coalescence, and it resulted in increased particle sizes for all emulsions. Larger aggregates were found in heated pH 7.0-SOB emulsions, and larger oil droplets were found in heated pH 11.0-SOB emulsions. After intestinal digestion, the droplets of all SOB emulsions gradually dispersed, and particle sizes decreased. Different heating temperatures had lesser effects on particle sizes and microstructures. Lipolysis was affected by the extraction pH and heating. For pH 11.0-SOB emulsions, the FFA release tendency was greatly affected by the heating temperature, and heating to 80 °C resulted in the highest FFA release (74%). However, all pH 7.0-SOB emulsions had similar total FFA releases. In addition, the droplet charges of heated pH 7.0-SOB emulsions were lower than those of unheated pH 7.0-SOB emulsions in both the intestine and stomach phases; however, the charge changes in different pH 11.0-SOB emulsions showed the opposite tendency. This study will offer guidance regarding the application of SOB emulsions in food.

Strategies for modulating the lipid digestion of emulsions in the gastrointestinal tract

The structural changes in emulsion products can be used to control the bioavailability of fatty acids and lipophilic compounds. After ingestion, lipid droplets undergo breakdown and structural changes as they pass through the gastrointestinal tract. The oil-water interface plays a critical role in modulating the digestive behavior of lipid droplets because changes in the interfacial layer control the adsorption of lipase and bile salts and determine the overall rate and extent of lipid digestion. Therefore, lipid digestibility can be tuned by selecting the appropriate types and levels of stabilizers. The stabilizer can change the lipase accessibility and exposure of lipid substrates, resulting in variable digestion rates. However, emulsified lipids are not only added to food matrixes but are also co-ingested from other dietary components. Therefore, overall consumption behaviors can affect the digestion rate and digestibility of emulsified lipids. Although designing an emulsion structure is challenging, controlling lipid digestion can improve the health benefits of products. Therefore, a thorough understanding of the process of emulsified lipid digestion is required to develop food products that enable specific physiological responses. The targeted or delayed release of lipophilic molecules and fatty acids through emulsion systems has significant applications in healthcare and pharmaceuticals.

Food biopolymer behaviors in the digestive tract: implications for nutrient delivery

Biopolymers are prevalent in both natural and processed foods, serving as thickeners, emulsifiers, and stabilizers. Although specific biopolymers are known to affect digestion, the mechanisms behind their influence on the nutrient absorption and bioavailability in processed foods are not yet fully understood. The aim of this review is to elucidate the complex interplay between biopolymers and their behavior in vivo, and to provide insights into the possible physiological consequences of their consumption. The colloidization process of biopolymer in various phases of digestion was analyzed and its impact on nutrition absorption and gastrointestinal tract was summarized. Furthermore, the review discusses the methodologies used to assess colloidization and emphasizes the need for more realistic models to overcome challenges in practical applications. By controlling macronutrient bioavailability using biopolymers, it is possible to enhance health benefits, such as improving gut health, aiding in weight management, and regulating blood sugar levels. The physiological effect of extracted biopolymers utilized in modern food structuring technology cannot be predicted solely based on their inherent functionality. It is essential to account for factors such as their initial consuming state and interactions with other food components to better understand the potential health benefits of biopolymers.

Pre-duodenal lipid digestion of emulsions: Relevance, colloidal aspects and mechanistic insight

The digestion of lipids in the human body has several health and nutritional implications. Lipid digestion is an interfacial phenomenon meaning that water-soluble lipases need to first adsorb to the oil-water interface before enzymatic conversions can start. The digestion of lipids mainly occurs on colloidal structures dispersed in water, such as oil-in-water (o/w) emulsions, which can be designed during food formulation/processing or structured during digestion. From a food design perspective, different in vitro studies have demonstrated that the kinetics of lipid digestion can be influenced by emulsion properties. However, most of these studies have been performed with pancreatic enzymes to simulate lipolysis in the small intestine. Only few studies have dealt with lipid digestion in the gastric phase and its subsequent impact on intestinal lipolysis. In this aspect, this review compiles information on the physiological aspects of gastric lipid digestion. In addition, it deals with colloidal and interfacial aspects starting from emulsion design factors and how they evolve during in vitro digestion. Finally, molecular mechanisms describing gastric lipolysis are discussed.

Competitive binding of maltodextrin and pectin at the interface of whey protein hydrolyzate-based fish oil emulsion under high temperature sterilization: Effects on storage stability and in vitro digestion

Whey protein hydrolysate (WPH), maltodextrin (MD), low methoxy pectin (LMP) and high methoxy pectin (HMP) were used to study the interface binding under high temperature sterilization conditions (121 °C, 15 min). The effect of competitive binding of MD and pectin with interface protein on the storage stability and gastrointestinal fate of fish oil emulsion was studied. The low-molecular-weight MD and the interface protein undergo a wide range of covalent binding through the Maillard reaction, while a small amount of high-molecular-weight pectin can form a protective shell with the interface protein through electrostatic interaction to inhibit the covalent reaction of MD, which was called competitive binding. However, due to the bridging and depletion flocculation of pectin, the emulsification stability of fish oil emulsion reduced. After 13 days of storage, compared with the particle size of the WPH fish oil emulsion (459.18 nm), the fish oil emulsion added with LMP and HMP reached 693.58 nm and 838.54 nm, respectively. In vitro digestion proved that WPH fish oil emulsion flocculated rapidly in the stomach (1.76 μm), while WPH-MD and WPH-MD-pectin fish oil emulsions flocculated slightly (less than800 nm). WPH-MD-pectin delayed digestion in the gastrointestinal tract, and HMP exhibited a better slow-release effect. This study provides reference for the design of multi-component functional drinks and other bioactive ingredient delivery system.

Progress in the Application of Food-Grade Emulsions

The detailed investigation of food-grade emulsions, which possess considerable structural and functional advantages, remains ongoing to enhance our understanding of these dispersion systems and to expand their application scope. This work reviews the applications of food-grade emulsions on the dispersed phase, interface structure, and macroscopic scales; further, it discusses the corresponding factors of influence, the selection and design of food dispersion systems, and the expansion of their application scope. Specifically, applications on the dispersed-phase scale mainly include delivery by soft matter carriers and auxiliary extraction/separation, while applications on the scale of the interface structure involve biphasic systems for enzymatic catalysis and systems that can influence substance digestion/absorption, washing, and disinfection. Future research on these scales should therefore focus on surface-active substances, real interface structure compositions, and the design of interface layers with antioxidant properties. By contrast, applications on the macroscopic scale mainly include the design of soft materials for structured food, in addition to various material applications and other emerging uses. In this case, future research should focus on the interactions between emulsion systems and food ingredients, the effects of food process engineering, safety, nutrition, and metabolism. Considering the ongoing research in this field, we believe that this review will be useful for researchers aiming to explore the applications of food-grade emulsions.

High-pressure processing of bovine milk: Effects on the coagulation of protein and fat globules during dynamic in vitro gastric digestion

The effect of high-pressure processing (HPP) on the digestion behavior of skim and whole bovine milks was investigated using a human gastric simulator. Both milks formed clots during gastric digestion. HPP treatment led to the formation of a coagulum with a fragmented and crumbled structure, compared with the coagulum formed from untreated milk. At pressures over 400 MPa, more intense pressure resulted in looser and more fragmented gastric clot structures. The weight of the dried clots and the moisture content in the clots of the skim milk treated at 600 MPa were significantly lower and higher than that of untreated skim milk, respectively. The looser and more fragmented gastric clot structures consequently led to faster hydrolysis of the proteins by pepsin during gastric digestion. The denaturation of the whey proteins induced by HPP may have also altered the resistance of α-lactalbumin and β-lactoglobulin in the HPP-treated milk samples to pepsin hydrolysis. This study provides insights into the differences among untreated skim milk, untreated whole milk and HPP-treated milk under in vitro gastric digestion conditions. The structure of the clots formed in the gastric environment affects their breakdown and consequently their emptying rate into the intestine.

Gastrointestinal Fate and Fatty Acid Release of Pickering Emulsions Stabilized by Mixtures of Plant Protein Microgels + Cellulose Particles: an In Vitro Static Digestion Study

The present study aims to investigate the in vitro intestinal digestion fate of Pickering emulsions with complex dual particle interfaces. Pickering oil-in-water emulsions (PPM-E) stabilized by plant (pea) protein-based microgels (PPM), as well as PPM-E where the interface was additionally covered by cellulose nanocrystals (CNC), were designed at acidic pH (pH 3.0). The gastrointestinal fate of the PPM-E and free fatty acid (FFA) release, was tested via the INFOGEST static in vitro digestion model and data was fitted using theoretical models. Lipid digestion was also monitored using lipase alone bypassing the gastric phase to understand the impact of proteolysis on FFA release. Coalescence was observed in the PPM-stabilized emulsions in the gastric phase, but not in those co-stabilized by CNC. However, coalescence occurred during the intestinal digestion stage, irrespective of the CNC concentration added (1–3 wt % CNC). The presence of CNC lowered the lipolysis kinetics but raised the extent of FFA release as compared to in its absence (p < 0.05), due to lower levels of gastric coalescence, i.e., a higher interfacial area. The trends were similar when just lipase was added with no prior gastric phase, although the extent and rate of FFA release was reduced in all emulsions, highlighting the importance of prior proteolysis in lipolysis of such systems. In summary, an electrostatically self-assembled interfacial structure of two types of oppositely-charged particles (at gastric pH) might be a useful strategy to enable enhanced delivery of lipophilic compounds that require protection in the stomach but release in the intestines.

Soy and whey protein isolate mixture/calcium chloride thermally induced emulsion gels: Rheological properties and digestive characteristics

We present the preparation and physicochemical properties of thermally induced emulsion gels of a soy protein isolate-whey protein isolate (SPI-WPI)/calcium chloride composite, and the analysis of their nutrient release behaviors using fat-soluble vitamin E as a model system by simulating its digestion in vitro. In general, the SPI-WPI composite emulsion gel was found to have better water-holding capacity and texture than the emulsion gels formed by the single protein. The microstructure and rheological properties of the gel suggested that the CaCl₂ concentration significantly influences the fundamental structure and mechanical properties of the SPI-WPI gel. The in vitro digestion experiments revealed that the mixed protein emulsion gel improves the bioavailability of vitamin E. This study is of great significance in the utilization of these natural emulsifiers, as they can be used in the development of emulsion delivery systems for lipophilic nutrients and other health products.

Ultrasonic Assisted Extraction of Quinoa (Chenopodium quinoa Willd.) Protein and Effect of Heat Treatment on Its In Vitro Digestion Characteristics

To extract and utilise the protein in quinoa efficiently, we investigated the effect of rate of quinoa protein isolate (QPI) extraction by ultrasound-assisted alkaline extraction and traditional alkaline extraction methods using single-factor experiments and Box-Behnken design. The effect of different heat treatment temperature and time on QPI functional properties and in vitro digestion characteristics were also investigated. The results showed that the optimal conditions of ultrasound- assisted alkaline extraction process were: ultrasonic time 99 min, solid-liquid ratio 1:20 w:v, ultrasonic temperature 47 °C, and pH 10, and its extraction rate and purity were 74.67 ± 1.08% and 87.17 ± 0.58%, respectively. It was 10.18% and 5.49% higher than that of the alkali-soluble acid precipitation method, respectively. The isoelectric point (pI) of QPI obtained by this method was 4.5. The flexibility and turbidity of QPI had maximum values at 90 °C, 30 min, and 121 °C, 30 min, which were 0.42 and 0.94, respectively. In addition, heat treatment changed the 1.77–2.79 ppm protein characteristic region in QPI’s nuclear magnetic resonance hydrogen spectroscopy (¹H NMR). After heating at 90 °C and 121 °C for 30 min, the hydrolysis degree and total amino acid content at the end of digestion (121 °C, 30 min) were significantly lower than those of untreated QPI by 20.64% and 27.85%. Our study provides basic data for the efficient extraction and utilisation of QPI.

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...

Lipid oxidation and aldehyde formation during in vitro gastrointestinal digestion of roasted scallop (Patinopecten yessoensis) - the role of added antioxidant of bamboo leaves

This study investigated lipid oxidation and aldehyde formation in roasted scallop during in vitro gastrointestinal digestion, and the effects of co-digestion of antioxidant of bamboo leaves (AOB) on this process. The results showed that the contents of lipid hydroperoxides (LOOH), conjugated dienes (CD), and Schiff bases (SB) were increased during gastrointestinal digestion. Besides, malondialdehyde (MDA) levels and total aldehyde formation decreased initially at the gastric stage but increased at the intestinal stage. The results of HPLC-ESI-MS/MS analysis showed that the contents of hexanal (HEX), trans, trans-2,4-octadienal (ODE), trans, trans-2,4-decadienal (DDE), 4-hydroxyhexenal (HHE) and 4-hydroxynonenal (HNE) in the digestive juices were all initially decreased and then increased during gastrointestinal digestion. Meanwhile, the content of acrolein, propanal, and trans-2-pentenal at the end of intestinal digestion was lower than that in the initial stage of gastric digestion. Additionally, the digestion of roasted scallop caused significant oxidation of polyunsaturated fatty acids (PUFAs) and release of free fatty acids (FFA) in the intestinal phase, which were positively related to aldehyde production. However, co-digestion of AOB significantly reduced lipid oxidation and formation of lipid oxidation products (LOOH, CD, SB, and aldehyde) during gastrointestinal digestion, indicating that the addition of AOB was effective in reducing gastrointestinal lipid oxidation.

Modification of the interfacial structure of droplet-stabilised emulsions during in vitro dynamic gastric digestion: Impact on in vitro intestinal lipid digestion

The in-vitro gastrointestinal digestion behaviour of an oil-in-water emulsion with an interface consisting of nano-sized droplets coated with caseinate particles, referred to as a droplet-stabilised emulsion (DSE), was explored using the human gastric simulator and pH-stat models. A caseinate-particle-stabilised emulsion (PSE) was used as a control, with a similar droplet size distribution and the same composition as the DSE. The nanodroplet-stabilised interface of the DSE was preserved during the first 180 min of gastric digestion. During 240 min, the droplet sizes of the DSE and the PSE increased from 22.71 ± 1.14 to 63.34 ± 6.57 μm and from 17.98 ± 1.16 to 85.11 ± 9.35 μm respectively. The small droplet size of the DSE that was released from the gastric phase contributed to slightly higher total free fatty acid (FFA) release (56.18 ± 3.55%) than that from the PSE (49.4 ± 2.67%). The FFA release rate of the DSE (1.21 % min^-1) was greater than that of the PSE (1.06 % min^-1) during the first 30 min of small intestinal digestion; similar FFA release rates (0.5 µmol s^-1 m^-2 × 10^-4) were obtained for both emulsions beyond 30 min of digestion. This study provides new information on lipid digestion using a novel interfacial layer that was stabilised with nanodroplets.

Dynamic gastric stability and in vitro lipid digestion of soybean protein isolate and three storage protein-stabilized emulsions: Effects of ultrasonic treatment

The emulsification of vegetable protein is closely related to solubility. The purpose of this study was to evaluate the effect of ultrasound on protein emulsification and to provide a prospective method for assessing the digestive properties of emulsions. In this article, we investigate the emulsion stability of ultrasonic pretreated soy protein isolate (SPI), and its three storage proteins, namely β-conglycinin (7S), lipophilic protein (LP), and glycinin (11S), under dynamic gastric conditions. The effects of these emulsions on lipolysis during digestion in the small intestine are also assessed using an in vitro dynamic human stomach simulator and a small intestine model. Particle size and ζ-potential measurements, as well as confocal laser scanning microscopy, revealed that during dynamic gastric digestion, the flocculation degree and floc size of 7S and soybean LP emulsions are larger than that of 11S and SPI emulsions. Meanwhile, ultrasound pretreatment of the proteins was found to prevent the agglomeration of the emulsion in a dynamic gastric environment. Moreover, enhanced flocculation delayed oil droplet delivery to the small intestine and subsequently retarded the release of lipophilic nutrients. The droplet size, molecular weight, and protein secondary structures of the ultrasonicated proteins were conducive to relatively higher rates and degrees of lipolysis in intestinal digestion than those of unsonicated proteins. Additionally, the slow-release effect of LP was superior to that of 11S and SPI, whereas 7S was comparatively more difficult to digest. The present study elucidated the fate of soy protein in the digestive tract and may facilitate microstructural food design to regulate physiological responses during digestion.

Gastric Emptying and Intragastric Behavior of Breast Milk and Infant Formula in Lactating Mothers

BACKGROUND

When sufficient breast milk is not available, infant formula is often used as an alternative. As for digestion, gastric behavior of infant formula and breast milk have not been studied in detail.

OBJECTIVE

This study aimed to compare gastric emptying and intragastric behavior between breast milk and infant formula in vivo using MRI.

METHODS

In this randomized crossover study, 16 lactating mothers (age: 31.7 ± 2.9 y; time since giving birth: 9.3 ± 2 mo), underwent gastric MRI scans before and after consumption of 200 mL of infant formula or their own breast milk. MRI scans were performed after an overnight fast (baseline) and every 10 min up until 60 min following ingestion. Primary outcomes were gastric emptying measures and the secondary outcome was gastric layer volume over time. Differences between infant formula and breast milk in total gastric volume and layering volume were tested using linear mixed models.

RESULTS

Gastric emptying half-time was 5.1 min faster for breast milk than for infant formula (95% CI: -19.0 to 29.2) (n = 14). Within a subgroup (n = 12) with similar initial gastric volume (<20 mL difference), gastric emptying half-time was 20 min faster for breast milk (95% CI: 1.23-43.1). Top layer volume (n = 16) was 6.4 mL greater for infant formula than for breast milk (95% CI: 1.9-10.8). This effect is driven by t = 10 and t = 20 min postingestion.

CONCLUSIONS

When taking initial gastric volume into account, breast milk emptied faster than infant formula in women, which is in line with previous findings in infants. Infant formula showed a significantly larger top layer volume in the first 20 min after ingestion. MRI in adults may find application in studies assessing gastric behavior of infant formula.

Kinetic Modeling of In Vitro Small Intestinal Lipid Digestion as Affected by the Emulsion Interfacial Composition and Gastric Prelipolysis

This research evaluated the impact of the emulsion interfacial composition on in vitro small intestinal lipolysis kinetics with the inclusion of rabbit gastric lipase resulting in a gastric prelipolysis step. O/w emulsions contained 5% triolein (w/w) and 1% (w/w) of the following emulsifiers: sodium taurodeoxycholate, citrus pectin, soy protein isolate, soy lecithin, and tween 80. Emulsions were subjected to static in vitro digestion and diverse lipolysis species quantified via a HPLC-charged aerosol detector. Single-response modeling indicated that the kinetics of lipolysis in the small intestinal phase were impacted by the emulsion particle size at the beginning of this phase. Multiresponse modeling permitted the elucidation of the lipolysis mechanism under in vitro conditions. The final reaction scheme included enzymatic and chemical conversions. The modeling strategies used in this research allowed to gain more insights into the kinetics and mechanism of in vitro lipid digestion.

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.

Impact of the Simulated Gastric Digestion Methodology on the In Vitro Intestinal Proteolysis and Lipolysis of Emulsion Gels

The aim of this work was to study the impact of the methodology of in vitro gastric digestion (i.e., in terms of motility exerted and presence of gastric emptying) and gel structure on the degree of intestinal proteolysis and lipolysis of emulsion gels stabilized by whey protein isolate. Emulsions were prepared at pH 4.0 and 7.0 using two homogenization pressures (500 and 1000 bar) and then the emulsions were gelled by heat treatment. These gels were characterized in terms of texture analysis, and then were subjected to one of the following gastric digestion methods: in vitro mechanical gastric system (IMGS) or in vitro gastric digestion in a stirred beaker (SBg). After gastric digestion, the samples were subjected to in vitro intestinal digestion in a stirred beaker (SBi). Hardness, cohesiveness, and chewiness were significantly higher in gels at pH 7.0. The degree of proteolysis was higher in samples digested by IMGS–SBi (7–21%) than SBg–SBi (3–5%), regardless of the gel’s pH. For SBg–SBi, the degree of proteolysis was not affected by pH, but when operating the IMGS, higher hydrolysis values were obtained for gels at pH 7.0 (15–21%) than pH 4.0 (7–13%). Additionally, the percentage of free fatty acids (%FFA) released was reduced by 47.9% in samples digested in the IMGS–SBi. For the methodology SBg–SBi, the %FFA was not affected by the pH, but in the IMGS, higher values were obtained for gels at pH 4.0 (28–30%) than pH 7.0 (15–19%). Our findings demonstrate the importance of choosing representative methods to simulate food digestion in the human gastrointestinal tract and their subsequent impact on nutrient bioaccessibility.

Chitin nanofibers improve the stability and functional performance of Pickering emulsions formed from colloidal zein

There is growing interest in formulating Pickering emulsions from biopolymer particles due to consumer demand for more natural products. Protein-based colloidal particles can be used for this purpose, but they are prone to aggregate at pH values around their isoelectric point (pI), which limits their application. In this study, the possibility of using chitin nanofibers (ChNFs) to improve the pH stability of Pickering emulsions prepared from zein colloidal particles (ZCPs) was investigated. Initially, the morphology and interfacial properties of the complexes formed between ChNFs and ZCPs were studied as a function of pH (3-9). The tendency of the ZCPs to aggregate and sediment at pH ≥ pI was reduced in the presence of ChNFs, which was attributed to the formation of electrostatic complexes. The contact angle of the composite particles could be optimized by altering their composition. For instance, the contact angle increased from 74° for ZCPs to 85° for ZCP/ChNF (5:1 ratio) at pH 6, which improved their tendency to stabilize the oil droplets. Brewster angle microscopy indicated that ZCP/ChNF complexes had rod-like and/or particulate structures at an air-water interface, which were different from those observed in the bulk aqueous phase. Pickering emulsions formed from ZCP/ChNF complexes had better stability than those formed from ZCPs or ChNFs, especially when the pH was close to or greater than the pI. An in vitro digestion study showed that the presence of the interfacial complexes reduced the lipolysis of the oil droplets by about 11% in a simulated gastrointestinal tract. High internal phase Pickering emulsions (HIPPEs) could be formed from ZCP/ChNF complexes at pH ≥ pI, which were able to protect unsaturated lipids from oxidation. Overall, our results show that chitin nanofibers can be used to improve the pH stability of Pickering emulsions formed from colloidal zein, as well as to modulate their functional performance.