Impact of Protein Gel Porosity on the Digestion of Lipid Emulsions

Walnut protein isolate based emulsion as a promising delivery system enhanced lutein bioaccessibility

Lutein, a natural pigment with multiple beneficial bioactivities, faces limitations in food processing due to its instability. In this study, we constructed four modified walnut protein isolate (WNPI) based emulsions as emulsion-based delivery systems (EBDS) for lutein fortification. The modification treatments enhanced the encapsulation efficiency of the WNPI-based EBDS on lutein. The modified WNPI-based EBDS exhibited improved storage and digestive stability, as well as increased lutein delivery capability in simulated gastrointestinal conditions. After in vitro digestion, the lutein retention in the modified WNPI-based EBDS was higher than in the untreated WNPI-based EBDS, with a maximum retention of 49.67 ± 1.10 % achieved after ultrasonic modification. Furthermore, the modified WNPI-based EBDS exhibited an elevated lutein bioaccessibility, reaching a maximum value of 40.49 ± 1.29 % after ultrasonic modification, nearly twice as high as the untreated WNPI-based EBDS. Molecular docking analysis indicated a robust affinity between WNPI and lutein, involving hydrogen bonds and hydrophobic interactions. Collectively, this study broadens WNPI's application and provides a foundation for fortifying other fat-soluble bioactive substances.

Development of Clindamycin-Releasing Polyvinyl Alcohol Hydrogel with Self-Healing Property for the Effective Treatment of Biofilm-Infected Wounds

Self-healing hydrogels have good mechanical strength, can endure greater external force, and have the ability to heal independently, resulting in a strong bond between the wound and the material. Bacterial biofilm infections are life-threatening. Clindamycin (Cly) can be produced in the form of a self-healing hydrogel preparation. It is noteworthy that the antibacterial self-healing hydrogels show great promise as a wound dressing for bacterial biofilm infection. In this study, we developed a polyvinyl alcohol/borax (PVA/B) self-healing hydrogel wound dressing that releases Cly. Four ratios of PVA, B, and Cly were used to make self-healing hydrogels: F1 (4%:0.8%:1%), F2 (4%:1.2%:1%), F3 (1.6%:1%), and F4 (4%:1.6%:0). The results showed that F4 had the best physicochemical properties, including a self-healing duration of 11.81 ± 0.34 min, swelling ratio of 85.99 ± 0.12%, pH value of 7.63 ± 0.32, and drug loading of 98.34 ± 11.47%. The B-O-C cross-linking between PVA and borax caused self-healing, according to FTIR spectra. The F4 formula had a more equal pore structure in the SEM image. The PVA/B-Cly self-healing hydrogel remained stable at 6 ± 2 °C for 28 days throughout the stability test. The Korsmeyer-Peppas model released Cly by Fickian diffusion. In biofilm-infected mouse wounds, PVA/B-Cly enhanced wound healing and re-epithelialization. Our results indicate that the PVA/B-Cly produced in this work has reliable physicochemical properties for biofilm-infected wound therapy.

Fabricating Pea Protein Micro-Gel-Stabilized Pickering Emulsion as Saturated Fat Replacement in Ice Cream

Unsaturated fat replacement should be used to reduce the use of saturated fat and trans fatty acids in the diet. In this study, pea protein micro-gels (PPMs) with different structures were prepared by microparticulation at pH 4.0-7.0 and named as PPM (pH 4.0), PPM (pH 4.5), PPM (pH 5.0), PPM (pH 5.5), PPM (pH 6.0), PPM (pH 6.5), and PPM (pH 7.0). Pea protein was used as a control to evaluate the structure and interfacial properties of PPMs by particle size distribution, Fourier transform infrared spectroscopy (FTIR), free sulfhydryl group content, and emulsifying property. PPM (pH 7.0) was suitable for application in O/W emulsion stabilization because of its proper particle size, more flexible structure, high emulsifying activity index (EAI) and emulsifying stability index (ESI). The Pickering emulsion stabilized by PPM (pH 7.0) had a uniform oil droplet distribution and similar rheological properties to cream, so it can be used as a saturated fat replacement in the manufacture of ice cream. Saturated fat was partially replaced at different levels of 0%, 20%, 40%, 60%, 80%, and 100%, which were respectively named as PR0, PR20, PR40, PR60, PR80, and PR100. The rheological properties, physicochemical indexes, and sensory properties of low-saturated fat ice cream show that PPM (pH 7.0)-stabilized emulsion can be used to substitute 60% cream to manufacture low-saturated fat ice cream that has high structural stability and similar melting properties, overrun, and sensory properties to PR0. The article shows that it is feasible to prepare low-saturated fat ice cream with PPM (pH 7.0)-stabilized Pickering emulsion, which can not only maintain the fatty acid profile of the corn oil used, but also possess a solid-like structure. Its application is of positive significance for the development of nutritious and healthy foods and the reduction of chronic disease incidence.

A Novel Artificial Coronary Plaque to Model Coronary Heart Disease

BACKGROUND

Experimental coronary artery interventions are currently being performed on non-diseased blood vessels in healthy animals. To provide a more realistic pathoanatomical scenario for investigations on novel interventional and surgical therapies, we aimed to fabricate a stenotic lesion, mimicking the morphology and structure of a human atherosclerotic plaque.

METHODS

In an interdisciplinary setting, we engineered a casting mold to create an atherosclerotic plaque with the dimensions to fit in a porcine coronary artery. Oscillatory rheology experiments took place along with long-term stability tests assessed by microscopic examination and weight monitoring. For the implantability in future in vivo setups, we performed a cytotoxicity assessment, inserted the plaque in resected pig hearts, and performed diagnostic imaging to visualize the plaque in its final position.

RESULTS

The most promising composition consists of gelatin, cholesterol, phospholipids, hydroxyapatite, and fine-grained calcium carbonate. It can be inserted in the coronary artery of human-sized pig hearts, producing a local partial stenosis and interacting like the atherosclerotic plaque by stretching and shrinking with the vessel wall and surrounding tissue.

CONCLUSION

This artificial atherosclerotic plaque model works as a simulating tool for future medical testing and could be crucial for further specified research on coronary artery disease and is going to help to provide information about the optimal interventional and surgical care of the disease.

Physicochemical properties and in vitro digestion behavior of emulsion gels stabilized by rice bran protein aggregates: Effects of heating time and induction methods

To investigate the effects of heating time and induction methods on the physicochemical properties and in vitro digestion behavior of emulsion gels, rice bran protein aggregates (RBPAs) were formed by acid-heat induction (90 °C, pH 2.0) and the emulsion gels were further prepared by adding GDL or/and laccase for single/double cross-linked induction. Heating time affected the aggregation and oil/water interfacial adsorption behavior of RBPAs. Suitable heating (1-6 h) was conducive to faster and more adsorption of aggregates at the oil/water interface. While excessive heating (7-10 h) resulted in protein precipitation, which inhibited the adsorption at the oil/water interface. The heating time at 2, 4, 5 and 6 h was thus chosen to prepare the subsequent emulsion gels. Compared with the single cross-linked emulsion gels, the double-cross-linked emulsion gels showed higher water holding capacity (WHC). After simulated gastrointestinal digestion, the single/double cross-linked emulsion gels all exhibited slow-release effect on free fatty acid (FFA). Moreover, the WHC and final FFA release rate of emulsion gels were closely related to the surface hydrophobicity, molecular flexibility, sulfhydryl, disulfide bond and interface behavior of RBPAs. Generally, these findings proved the potential of emulsion gels in designing fat alternatives, which could provide a novel technique for the fabrication of low-fat food.

Intermolecular forces regulate in-vitro digestion of whey protein emulsion gels: Towards controlled lipid release

HYPOTHESIS

The utilization of emulsion-filled protein hydrogels for controlled lipid release in the gastrointestinal tract (GIT) displays great potential in drug delivery and obesity treatment. However, how intermolecular interactions among protein molecules influence lipid digestion of the gels is still understudied.

EXPERIMENTS

Differently structured whey protein emulsion gels were fabricated by heating emulsions with blocking of disulfide bonds (the "noncovalent" gel), noncovalent interactions (the "disulfide" gel), or neither of these (the "control" gel). The intermolecular interactions-gel structure-lipid digestion relationship was investigated by characterizing structural/mechanical properties of the gels and monitoring their dynamic breakdown in a simulated GIT.

FINDINGS

Although the disulfide-crosslinked protein network formed thick interfacial layers around oil droplets and resisted intestinal proteolysis, the "disulfide" gel had the fastest lipolysis rate, indicating that it could not inhibit the access of lipases to oil droplets. In contrast, the "noncovalent" gel was more susceptible to in-vitro digestion than the "control" gel because of lower gel strength, resulting in a faster lipolysis rate. This demonstrated that intermolecular disulfide bonds and noncovalent interactions played distinctive roles in the digestion of the gels; they represented the structural backbone and the infill in the gel structure, respectively.

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.

Ultra-stable liquid crystal droplets coated by sustainable plant-based materials for optical sensing of chemical and biological analytes

Herein, we demonstrate for the first time the synthesis of ultra-stable, spherical, nematic liquid crystal (LC) droplets of narrow size polydispersity coated by sustainable, biodegradable, plant-based materials that trigger a typical bipolar-to-radial configurational transition in dynamic response to chemical and biological analytes. Specifically, a highly soluble polymer, potato protein (PoP) and a physically-crosslinked potato protein microgel (PoPM) of ∼100 nm in diameter, prepared from the PoP, a byproduct of the starch industry, were compared for their ability to coat LC droplets. Although both PoP and PoPM were capable of reducing the interfacial tension between water and n-tetradecane <30 mN m^-1, PoPM-coated LC droplets showed better stability than the PoP-coated droplets via a Pickering-like mechanism. Strikingly, the Pickering LC droplets outperformed PoP-stabilized droplets in terms of dynamic response with 5× lower detection limit to model chemical analytes (sodium dodecyl sulphate, SDS) due to the difference in SDS-binding features between the protein and the microgel. To eliminate the effect of size polydispersity on the response, monodisperse Pickering LC droplets of diameter ∼16 μm were additionally obtained using microfluidics, which mirrored the response to chemical as well as biological analytes, i.e., primary bile acid, an important biomarker of liver diseases. We demonstrate that these eco-friendly microgels used for creating monodisperse, ultra-stable, LC complex colloids are powerful templates for fabricating next generation, sustainable optical sensors for early diagnosis in clinical settings and other sensing applications.

How macronutrients and pancreatic enzyme supplements dose variability affect fat, protein and starch absorption in children with cystic fibrosis

BACKGROUND

low evidence on the dose of enzymatic supplements used in pancreatic enzyme replacement therapy (PERT) is available.

AIM

assessing if fat, protein and starch absorption could be related to the dose of the enzymatic supplement, the intra-patient variability in the dose and macronutrient intake.

METHODS

Four-day food records and 3-day faecal samples were prospectively collected in 69 children with cystic fibrosis. Pearson correlations between enzyme dose and macronutrient absorption, and beta regression models were applied to explain the results.

RESULTS

the supply of protease units per protein intake (PU/g protein) in relation to lipase units per fat intake (LU/g fat) was low and the intra-patient variability in the dose of enzymes was ±1331 LU/g fat. Fat and starch absorption was >90% while for protein it was 81.5%. The coefficient of fat absorption was associated with an interaction between the dose of LU/g fat and its variability among different days. Lipid and protein intake were also determinants of the coefficient of fat absorption.

CONCLUSION

the dose of PERT should be re-adjusted to the amount of dietary fat of every meal (constant LU/g fat) to minimize variability and increase fat absorption. Also, the supply of protease should be increased to prevent from protein malabsorption.

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.

In vitro digestion of designed emulsions based on milk protein and guar gum systems

There is a growing interest in designing novel food microstructures that can control nutrient digestion and provide satiety for tackling obesity. In this study, phase separated microstructures of skimmed milk powder (SMP) and guar gum (GG) were the main focus, and these can be considered as water-in-water (W/W) emulsions. Through the incorporation of oil into these systems, it was possible to form model systems of SMP-GG-OIL, showing the lipid phase within the protein phase within the polysaccharide phase. The in vitro digestibility of such phase separated model systems of SMP-GG-OIL with different microstructures was investigated using a pH stat method. Confocal laser scanning microscopy also revealed structural changes that occurred to the emulsified lipid droplets as they passed through a gastrointestinal (GI) model. The microstructures were created based on the tie-lines on a previously established phase diagram of SMP-GG, and shown to be able to control lipid digestion. For a selected tie-line, the lipolysis follows the order: protein continuous > bi-continuous > polysaccharide continuous system, at a certain level of oil addition. The mechanism involved in the lipolysis of the designed formulations/microstructures was dependent upon the protein, rather than GG, and was driven by the protein concentration. These findings provide insights for potential applications in functional food designing in the food industry.

Preparation and Characterization of a Novel Soy Protein Isolate-Sugar Beet Pectin Emulsion Gel and Its Application as a Multi-Phased Nutrient Carrier

Emulsion gel, a novel oral delivery carrier, provides the possibility to co-load hydrophilic and lipophilic nutrients simultaneously. In this study, duo-induction methods of laccase and glucono-δ-lactone (L&GDL) or laccase and transglutaminase (L&MTG) were used to prepare the soy protein isolate-sugar beet pectin (SPI-SBP) emulsion gel. The textural data of the emulsion gel was normalized to analyze the effect of different induction methods on the gel property of the SPI-SBP emulsion gels. The characterization studies showed the structure of L&MTG emulsion gel was denser with a lower swelling ratio and reduced degree of digestion, compared with L&GDL emulsion gel. Moreover, the release profiles of both β-carotene and riboflavin co-loaded in the SPI-SBP emulsion gels were correlated to the digestion patterns of the gel matrix; the controlled-release of encapsulated functional factors was regulated by a gel network induced by different induction methods, mainly due to the resulting porosity of the structure and swelling ratio during digestion. In conclusion, SPI-SBP emulsion gels have the capability of encapsulating multiple functional factors with different physicochemical properties.

Impact of gastric coagulation on the kinetics of release of fat globules from milk of different species

The behavior of fat globules during the gastric digestion of raw and pasteurized cow, goat, and sheep whole milks was studied using a human gastric simulator. Microstructural and physicochemical analysis revealed that, initially, the coagulation of the milks in the human gastric simulator resulted in the majority of the milk fat globules being entrapped within the curd. As the digestion progressed, the proportion of fat globules entrapped within the aggregated protein matrix (curd) decreased; there was also some flocculation as well as coalescence of the fat globules within the curd. The liberation of the entrapped fat globules from the curd to the liquid phase of the chyme was strongly dependent on the disintegration and hydrolysis of the structured casein network. Surprisingly, the fat globules released (or already present) into the liquid phase of the chyme were not as extensively coalesced as those remaining within the curd. These phenomena were observed to be similar for the raw and pasteurized whole milk of all species. The pasteurized whole milks from all species formed relatively less structured coagula compared with their raw milk counterparts, leading to a greater extent of protein breakdown and, thus, higher proportions of fat release from the pasteurized milk curds. This study provides a deeper understanding of how the curd-forming properties of different mammalian milks in the gastric environment provide controlled delivery of nutrients (such as protein and fat).

The effect of pore size on the diffusion of volatile antimicrobials is a key factor to preserve gelled foods

This study aimed to understand how the microstructure of gelled foods impacts the diffusion of a volatile antimicrobial compound and its efficacy at different depths from the surface. Carvacrol-loaded polylactic acid film was used to inhibit the growth of Pseudomonas fluorescens in WPI-carrageenan gels during storage at 4 °C. The diffusion of antimicrobials was increased in gels having larger average pore size. The antimicrobial efficacy of the antimicrobial packaging was dependent on the diffusion of carvacrol within the gels. The final concentration of carvacrol in the top layer was more than 4 fold higher than that in the middle layer and more than 13-fold higher than that in the bottom layer, resulting in a more effective inhibition in the top layer than those in the middle and bottom layers. Our study demonstrates the importance of considering the diffusion of antimicrobials in solid/semi-solid foods in the antimicrobial packaging design.

Physicochemical properties and digestive kinetics of whey protein gels filled with potato and whey protein mixture emulsified oil droplets: effect of protein ratios

Incorporating protein emulsified droplets into protein gels as active fillers have attracted much attention. However, using animal and plant protein mixtures emulsified droplets as the filler is lacking. We investigated the effect of emulsified droplets covered by potato protein (PP) and whey protein (WP) mixtures of different ratios (10/0, 9/1, 7/3, 5/5, 3/7, 1/9, 0/10) on mechanical, microstructural characteristics and digestion of emulsion-filled WP gels (EFWG). The results showed that the particle size of emulsified droplets increased with the enhancement of PP ratio, whereas their ζ-potential value decreased. Increasing the PP ratio improved the elastic moduli (G'), fracture stress and hardness of EFWG, while lowered the water holding capacity and swelling ratios of EFWG. Confocal laser scanning microscopy revealed that a higher PP ratio leads to a thicker gel skeleton and fine network. Although the enhancement of the PP ratio decreased disulfide bond content in EFWG, it improved the hydrogen bond and total non-covalent interactions in EFWG. Increased PP in filling emulsions delayed the release rate of the free amino group and free fatty acid during digestion. Moreover, the presence of NaCl improved the gel properties and digestion of EFWG. The findings of this study may provide information for developing new WP gel products with specific digestion rates.

Cellulose and cellulose derivatives: Different colloidal states and food-related applications

Development of new sources and isolation processes has recently enhanced the production of cellulose in many different colloidal states. Even though cellulose is widely used as a functional ingredient in the food industry, the relationship between the colloidal states of cellulose and its applications is mostly unknown. This review covers the recent progress on illustrating various colloidal states of cellulose and the influencing factors with special emphasis on the correlation between the colloidal states of cellulose and its applications in food industry. The associated unique colloidal states of cellulose like high aspect ratio, crystalline structure, surface charge, and wettability not only promote the stability of colloidal systems, but also help improve the nutritional aspects of cellulose by facilitating its interactions with digestive system. Further studies are required for the rational control and improvement of the colloidal states of cellulose and producing food systems with enhanced functional and nutritional properties.

Protein Microgel-Stabilized Pickering Liquid Crystal Emulsions Undergo Analyte-Triggered Configurational Transition

Herein, we report a novel approach that involves Pickering stabilization of micometer-sized liquid crystal (LC) droplets with biocompatible soft materials such as a whey protein microgel (WPM) to facilitate the analysis of analyte-induced configurational transition of the LC droplets. The WPM particles were able to irreversibly adsorb at the LC-water interface, and the resulting WPM-stabilized LC droplets possessed a remarkable stability against coalescence over time. Although the LC droplets were successfully protected by a continuous network of the WPM layer, the LC-water interface was still accessible for small molecules such as sodium dodecyl sulfate (SDS) that could diffuse through the meshes of the adsorbed WPM network or through the interfacial pores and induce an LC response. This approach was exploited to investigate the dynamic range of the WPM-stabilized LC droplet response to SDS. Nevertheless, the presence of the unadsorbed WPM in the aqueous medium reduced the access of SDS molecules to the LC droplets, thus suppressing the configuration transition. An improved LC response to SDS with a lower detection limit was achieved after washing off the unadsorbed WPM. Interestingly, the LC exhibited a detection limit as low as ∼0.85 mM for SDS within the initial WPM concentration ranging from 0.005 to 0.1 wt %. Furthermore, we demonstrate that the dose-response behavior was strongly influenced by the number of droplets exposed to the aqueous analytes and the type of surfactants such as anionic SDS, cationic dodecyltrimethylammonium bromide (DTAB), and nonionic tetra(ethylene glycol)monododecyl ether (C₁₂E₄). Thus, our results address key issues associated with the quantification of aqueous analytes and provide a promising colloidal platform toward the development of new classes of biocompatible LC droplet-based optical sensors.

Physical chemistry of gastric digestion of proteins gels

In this paper, we present the rich physics and chemistry of the gastric digestion of protein gels. Knowledge of this matter is important for the development of sustainable protein foods that are based on novel proteins sources like plant proteins or insects. Their digestibility is an important question in the design of these new protein foods. As polyelectrolyte gels, they can undergo volume changes upon shifts in pH or ionic strengths, as protein gels experience when entering the gastric environment. We show that these volume changes can be modelled using the Flory-Rehner theory, combined with Gibbs-Donnan theory accounting for the distribution of electrolytes over gel and bath. In-vitro experiments of soy protein gels in simulated gastric fluid indeed show intricate swelling behaviour, at first the gels show swelling but at longer times they shrink again. Simulations performed with the Flory-Rehner/Gibbs-Donnan theory reproduce qualitatively similar behaviour. In the final part of the paper, we discuss how the model must be extended to model realistic conditions existing in the in-vivo gastric environment.

Design principles of food gels

Naturally sourced gels from food biopolymers have advanced in recent decades to compare favourably in performance and breadth of application to their synthetic counterparts. Here, we comprehensively review the constitutive nature, gelling mechanisms, design approaches, and structural and mechanical properties of food gels. We then consider how these food gel design principles alter rheological and tribological properties for food quality improvement, nutrient-modification of foods while preserving sensory perception, and targeted delivery of drugs and bioactives within the gastrointestinal tract. We propose that food gels may offer advantages over their synthetic counterparts owing to their source renewability, low cost, biocompatibility and biodegradability. We also identify emerging approaches and trends that may improve and expand the current scope, properties and functionalities of food gels and inspire new applications.

Hierarchically structured phase separated biopolymer hydrogels create tailorable delayed burst release during gastrointestinal digestion

The on demand delivery of novel peptide actives, traditional pharmaceuticals, nutrients and/or vitamins is a ever present challenge due to the digestive and metabolic degradation of the active and the delivery vehicle. Biodegradable biopolymer hydrogels have long held promise as candidates for creating tailored release profiles due to the ability to control gel porosity. The present study describes the creation of novel hierarchical biopolymer hydrogels for the controlled release of lipids/lipophilic actives pharmaceutical ingredients (APIs), and mathematically describes the mechanisms that affect the timing of release. The creation of phase separated protein/polysaccharide core (6.6 wt% gelatin, 40 wt% Oil in water emulsion) shell structures (7 g/L xanthan with 70-140 g/L β-lactoglobulin) altered enzyme mass transport processes. This core shell structure enabled the creation of a tailorable burst release of API during gastrointestinal digestion where there is a delay in the onset of release, without affecting the kinetics of release. The timing of the delay could be readily programmed (with release of between 60 and 240 min) by controlling either the thickness or protein concentration (between 70 g/L and 140 g/L β-lactoglobulin) of the outer mixed biopolymer hydrogel shell (7 g/L xanthan with 70-140 g/L β-lactoglobulin). Enzyme diffusion measurements demonstrated that surface erosion was the main degradation mechanism. A kinetic model was created to describe the delayed burst release behaviour of APIs encapsulated within the core, and successfully predicted the influence of shell thickness and shell protein density on the timing of gastro-intestinal release (in vitro). Our work highlights the creation of a novel family of core-shell hydrogel oral dosage forms capable of programmable delivery of lipids/lipophilic APIs. These findings could have considerable implications for the delivery of peptides, poorly soluble drugs, or the programmed delivery of lipids within the gastrointestinal tract.

Microstructured Fibers for the Production of Food

Food engineering faces the difficult challenge of combining taste, i.e., tailoring texture and rheology of food matrices with the balanced intake of healthy nutrients. In materials science, fiber suspensions and composites have been developed as a versatile and successful approach to tailor rheology while imparting materials with added functionalities. Structures based on such types of physical (micro)fibers are however rare in food production mainly due to a lack of food-grade materials and processes allowing for the fabrication of fibers with controlled sizes and microstructures. Here, the controlled fabrication of multi-material microstructured edible fibers is demonstrated using a food compatible process based on preform-to-fiber thermal drawing. It is shown that different material systems based on gelatin or casein, with plasticizers such as glycerol, can be thermally drawn into fibers with various geometries and cross-sectional structures. It is demonstrated that fibers can exhibit tailored mechanical properties post-drawing, and can encapsulate nutrients to control their release. The versatility of fiber materials is also exploited to demonstrate the fabrication of food-grade fabrics and scaffolds for food growth. The end results establish a new field in food production that relies on fiber-based simple and eco-friendly processes to realize enjoyable yet healthy and nutritious products.

Colloidal aspects of digestion of Pickering emulsions: Experiments and theoretical models of lipid digestion kinetics

Lipid digestion is a bio-interfacial process that is largely governed by the binding of the lipase-colipase-biosurfactant (bile salts) complex onto the surface of emulsified lipid droplets. Therefore, engineering oil-water interfaces that prevent competitive displacement by bile salts and/or delay the transportation of lipase to the lipidoidal substrate can be an effective strategy to modulate lipolysis in human physiology. In this review, we present the mechanistic role of Pickering emulsions i.e. emulsions stabilised by micron-to-nano sized particles in modulating the important fundamental biological process of lipid digestion by virtue of their distinctive stability against coalescence and resilience to desorption by intestinal biosurfactants. We provide a systematic summary of recent experimental investigations and mathematical models that have blossomed in the last decade in this domain. A strategic examination of the behavior and mechanism of lipid digestion of droplets stabilised by particles in simulated biophysical environments (oral, gastric, intestinal regimes) was conducted. Various particle-laden interfaces were considered, where the particles were derived from synthetic or biological sources. This allowed us to categorize these particles into two classes based on their mechanistic role in modifying lipid digestion. These are 'human enzyme-unresponsive particles' (e.g. silica, cellulose, chitin, flavonoids) i.e. the ones that cannot to be digested by human enzymes, such as amylase, protease and 'human enzyme-responsive particles' (e.g. protein microgels, starch granules), which can be readily digested by humans. We focused on the role of particle shape (spherical, anisotropic) on modifying both interfacial and bulk phases during lipolysis. Also, the techniques currently used to alter the kinetics of lipid digestion using intelligent physical or chemical treatments to control interfacial particle spacing were critically reviewed. A comparison of how various mathematical models reported in literature predict free fatty acid release kinetics during lipid digestion highlighted the importance of the clear statement of the underlying assumptions. We provide details of the initial first order kinetic models to the more recent models, which account for the rate of adsorption of lipase at the droplet surface and include the crucial aspect of interfacial dynamics. We provide a unique decision tree on model selection, which is appropriate to minimize the difference between experimental data of free fatty acid generation and model predictions based on precise assumptions of droplet shrinkage, lipase-binding rate, and nature of lipase transport process to the particle-laden interface. Greater insights into the mechanisms of controlling lipolysis using particle-laden interfaces with appropriate mathematical model fitting permit better understanding of the key lipid digestion processes. Future outlook on interfacial design parameters, such as particle shape, size, polydispersity, charge, fusion, material chemistry, loading and development of new mathematical models that provide closed-loop equations from early to later stages of kinetics are proposed. Such future experiments and models hold promise for the tailoring of particle-laden interfaces for delaying lipid digestion and/or site-dependent controlled release of lipidic active molecules in composite soft matter systems, such as food, personal care, pharmaceutical, healthcare and biotechnological applications.

In Vitro Digestion of Oil-in-Water Emulsions Stabilized by Regenerated Chitin

Regenerated chitin (R-chitin) can stabilize oil-in-water (O/W) emulsions containing up to 50% oil at a low chitin dosage of 2 mg/g oil. The mean droplet size of the resulting emulsion decreased as more R-chitin was used. Confocal laser scanning microscopy (CLSM) demonstrated the adsorption of R-chitin on emulsion droplets surface, confirming the emulsions were stabilized via Pickering mechanism. The effects of R-chitin concentration on storage stability, microstructure, and lipid digestion properties were investigated. Pickering emulsions stabilized by R-chitin above 1.0% w/w exhibited outstanding physical stability against coalescence and Ostwald ripening. In particular, highly consistent emulsions that remained almost unchanged during oral, gastric, and intestine digestion could be prepared using R-chitin. The emulsions could enhance fullness and satiety perceptions at gastric level, and R-chitin could be used as a substitute for food emulsifiers for weight management via increasing satiation perception and reducing lipid digestion.

In Vitro Digestion of Lipids in Real Foods: Influence of Lipid Organization Within the Food Matrix and Interactions with Nonlipid Components

In vitro digestion research has scarcely addressed the assessment of the complexity of digestion in real food. The aim of the present study was to evaluate the influence of intestinal conditions, nonlipid components, and lipid organization within the food matrix on lipolysis extent. A selection of 52 foods was studied under different simulated intestinal conditions, including those related to patients with cystic fibrosis (pH6, bile salts 1 mM due to decreased pancreatic and biliary secretions) and to healthy subjects (pH7, bile salts 10 mM). Linear mixed regression models were applied to explain associations of food properties with lipolysis. Normal intestinal conditions allowed for optimal lipolysis in most of the foods in contrast to the altered intestinal scenario (30 compared with 1 food reaching > 90% lipolysis). Lipid-protein and lipid-starch interactions were evidenced to significantly affect lipolysis (P < 0.001) in all the digestion conditions, decreasing in those foods with low fat and high protein or high starch content. In addition, under decreased intestinal pH and bile concentration, lipolysis was lower in foods with complex solid structures and continuous lipid phase than in the oil-in-water continuous aqueous phase (global P < 0.01). However, in the normal conditions lipid organization within the food matrix did not show a significant effect on lipolysis (global P = 0.08). In conclusion, food properties play a crucial role in lipolysis, which should be considered when establishing dietary recommendations.

PRACTICAL APPLICATION

Food composition, lipid organization within the food matrix, and gastrointestinal conditions are key factors affecting lipolysis. Knowledge on that can be used to modulate lipolysis performance after food ingestion. Different applications are foreseen, as food design and nutritional recommendations for the general populations and specific target groups. The most immediate application is related to the scope of the research project that frames this work (www.mycyfapp.eu). These results have contributed to the development of a mobile app for cystic fibrosis patients, which includes an algorithm for enzyme dose prediction based on food properties. The app is currently being tested in a clinical trial setting.

Engineering intelligent particle-lipid composites that control lipase-mediated digestion

Nanostructured particle-lipid composites have emerged as state-of-the-art carrier systems for poorly water-soluble bioactive molecules due to their ability to control and enhance the lipase-mediated hydrolysis of encapsulated triglycerides, leading to a subsequent improvement in the solubilisation and absorption of encapsulated species. The first generation of particle-lipid composites (i.e. silica-lipid hybrid (SLH) microparticles) were designed and fabricated by spray drying a silica nanoparticle-stabilised Pickering emulsion, to create a novel three-dimensional architecture, whereby lipid droplets were encapsulated within a porous matrix support. The development of SLH microparticles has acted as a solid foundation for the synthesis of several next generation particle-lipid composites, including polymer-lipid hybrid (PLH) and clay-lipid hybrid systems (CLH), which present lipase with unique lipid microenvironments for optimised lipolysis. This review details the methods utilised to engineer lipid hybrid particles and the strategic investigations that have been performed to determine the influence of key material characteristics on digestion enzyme activity. In doing so, this provides insight into manipulating the mechanism of lipase action through the intelligent design of lipid-based biomaterials for their use in drug delivery formulations and novel functional foods.

Microgel-in-Microgel Biopolymer Delivery Systems: Controlled Digestion of Encapsulated Lipid Droplets under Simulated Gastrointestinal Conditions

Structural design principles are increasingly being used to develop colloidal delivery systems for bioactive agents. In this study, oil droplets were encapsulated within microgel-in-microgel systems. Initially, a nanoemulsion was formed that contained small whey protein-coated oil droplets ( d₄₃ = 211 nm). These oil droplets were then loaded into either carrageenan-in-alginate (O/M_C/M_A) or alginate-in-carrageenan (O/M_A/M_C) microgels. A vibrating nozzle encapsulation unit was used to form the smaller inner microgels ( d₄₃ = 170-324 μm), while a hand-held syringe was used to form the larger outer microgels ( d₄₃ = 2200-3400 μm). Calcium alginate microgels (O/M_A) were more stable to simulated gastrointestinal tract (GIT) conditions than potassium carrageenan microgels (O/M_C), which was attributed to the stronger cross-links formed by divalent calcium ions than the monovalent potassium ions. As a result, the microgel-in-microgel systems had different gastrointestinal fates depending upon the nature of the external microgel phase; i.e., the O/M_C/M_A system was more resistant to rupture than the O/M_A/M_C system. The rate of lipid digestion under simulated small intestine conditions decreased in the following order: free oil droplets > O/M_C > O/M_A > O/M_A/M_C > O/M_C/M_A. This effect was attributed to differences in the integrity and dimensions of the microgels in the small intestine, because a hydrogel network surrounding the oil droplets inhibits lipid hydrolysis by lipase. The structured microgels developed in this study may have interesting applications for the protection or controlled release of bioactive agents.

The Physical State of Emulsified Edible Oil Modulates Its in Vitro Digestion

Emulsified lipid digestion was tailored by manipulating the physical state of dispersed oil droplets in whey protein stabilized oil-in-water (O/W) emulsions, where the oil phase consisted of one of five ratios of soybean oil (SO) and fully hydrogenated soybean oil (FHSO). The evolution in particle size distribution, structural changes during oral, gastric, and intestinal digestion, and free fatty acid release during intestinal digestion were all investigated. Irrespective of the physical state and structure of the dispersed oil/fat, all emulsions were stable against droplet size increases during oral digestion. During gastric digestion, the 50:50 SO:FHSO emulsion was more stable against physical breakdown than any other emulsion. All emulsions underwent flocculation and coalescence or partial coalescence upon intestinal digestion, with the SO emulsion being hydrolyzed the most rapidly. The melting point of all emulsions containing FHSO was above 37 °C, with the presence of solid fat within the dispersed oil droplets greatly limiting lipolysis. Fat crystal polymorph and nanoplatelet size did not play an important role in the rate and extent of lipid digestion. Free fatty acid release modeled by the Weibull distribution function showed that the rate of lipid digestion (κ) decreased with increasing solid fat content, and followed an exponential relationship (R² = 0.95). Overall, lipid digestion was heavily altered by the physical state of the dispersed oil phase within O/W emulsions.