Influence of chitosan coating on protein-based nanohydrogels properties and in vitro gastric digestibility

Comparison and analysis of mechanism of β-lactoglobulin self-assembled gel carriers formed by different gelation methods

Based on the findings of our previous studies, a comprehensive comparative investigation of the quality and formation mechanism of gels obtained from protein self-assemblies induced by different methods is necessary. Self-assembled heat-induced gels had higher gel mechanical strength, and hydrophobic interactions played a greater role. Whether or not heat treatment was used to induce gel formation may play a more important role than the effect of divalent cations on gel formation. Hydrogen bonds played an important role in all gels formed using different gelation methods. Furthermore, Self-assembled cold-induced gels were considered to can load bioactive substances with different hydrophilicity properties due to the high water-holding capacity and the smooth, dense microstructure. Therefore, β-lactoglobulin fibrous and worm-like self-assembled cold-induced gels as a delivery material for hydrophilic bioactive substances (epigallocatechin gallate, vitamin B2) and amphiphilic bioactive substance (naringenin), with good encapsulation efficiency (91.92 %, 97.08 %, 96.72 %, 96.52 %, 98.94 %, 97.41 %, respectively) and slow-release performance.

Fucoidan alleviates the inhibition of protein digestion by chitosan and its oligosaccharides

Chitosan (CTS) and chitosan oligosaccharides (COS) have been widely applied in food industry due to their bioactivities and functions. However, CTS and COS with positive charges could interact with proteins, such as whey protein isolate (WPI), influencing their digestion. Interaction among CTS/COS, FUC, and WPI/enzymes was studied by spectroscopy, chromatography, and chemical methods in order to reveal the role of FUC in relieving the inhibition of protein digestibility by CTS/COS and demonstrate the action mechanisms. As shown by the results, the addition of FUC increased degree of hydrolysis (DH) and free protein in the mixture of CTS and WPI to 3.1-fold and 1.8-fold, respectively, while raise DH value and free protein in the mixture of COS and WPI to 6.7-fold and 1.2-fold, respectively. The interaction between amino, carboxyl, sulfate, and hydroxyl groups from carbohydrates and protein could be observed, and notably, FUC could interact with CTS/COS preferentially to prevent CTS/COS from combining with WPI. In addition, the addition of FUC could also relieve the combination of CTS to trypsin, increasing the fluorescence intensity and concentration of trypsin by 83.3 % and 4.8 %, respectively. Thus, the present study demonstrated that FUC could alleviate the inhibitory effect of CTS/COS on protein digestion.

Design, characterization and digestibility of β-carotene-loaded emulsion system stabilized by whey protein with chitosan and potato starch addition

The physicochemical properties and gastrointestinal fate of β-carotene-loaded emulsions and emulsion gels were examined. The emulsion was emulsified by whey protein isolate and incorporated with chitosan, then the emulsion gels were produced by gelatinizing potato starch in the aqueous phase. The rheology properties, water distribution, and microstructure of emulsions and emulsion gels were modulated by chitosan combination. A standardized INFOGEST method was employed to track the gastrointestinal fate of emulsion systems. Significant changes in droplet size, zeta-potential, and aggregation state were detected during in vitro digestion, including simulated oral, stomach, and small intestine phases. The presence of chitosan led to a significantly reduced free fatty acids release in emulsion, whereas a slightly increasing released amount in the emulsion gel. β-carotene bioaccessibility was significantly improved by hydrogel formation and chitosan addition. These results could be used to formulate advanced emulsion systems to improve the gastrointestinal fate of hydrophobic nutraceuticals.

Characterization and emulsifying ability evaluation of whey protein-pectin conjugates formed by glycosylation

Glycosylation is a method that enhances the functional properties of proteins by covalently attaching sugars to them. This study aimed at preparing three conjugates (WP-HG, WP-SBP, and WP-RGI) by dry heating method to research the influence of different pectin structures on the functional properties of WP and characterize properties and structures of these conjugates. The research results manifested that the degree of glycosylation (DG) of HG, SBP and RGI were 13.13 % ± 0.07 %, 23.27 % ± 0.3 % and 36.39 % ± 0.3 % respectively, suggesting that the increase of the number of branch chains promoted the glycosylation reaction. The formation of the conjugate was identified by the FT-IR spectroscopy technique. And SEM showed that WP could covalently bind to pectin, resulting in a smoother and denser surface of the conjugates. The circular dichroism analysis exhibited that the glycosylation reaction altered the secondary structure of WP and decreased the α-Helix content. This structural change in the protein spatial conformation led to a decrease in the hydrophobicity of protein surface. But the addition of pectin further regulated the hydrophilic-hydrophobic ratio on the surface of the protein, thus improving the emulsification properties of WP. In addition, the glycosylation could improve the stability of the emulsion, giving it a smaller droplet size, higher Zeta-potential and more stable properties. In a word, this study pointed out the direction for the application of different pectin structures in the development of functional properties of glycosylation products in food ingredients.

Undenatured type II collagen nanofibrils with sodium alginate coating: Structural characterization, physicochemical properties and capability to load curcumin

In this study, the structural design and physicochemical property enhancement of undenatured type II collagen (UC-II) nanofibrils with sodium alginate (SA) coating induced by calcium ions (Ca2+) were investigated. The research aimed to elucidate the impact of Ca2+ concentration on the morphology, thermal stability, and digestive resistance, as well as to assess the potential of UC-II/SA nanofibrils as a delivery system for curcumin (Cur). A series of Ca2+ concentrations (1-9 mM) were methodically applied to optimize the condition that maintains the triple-helical structure of UC-II, thereby enhancing its functional properties. It was found that the Ca2+ level up to 5 mM effectively preserved the structural integrity and improved thermal stability of UC-II, with the added benefit of ensuring the substantial delivery of active fragment to small intestine (70.7 %), which was 3.43 times greater than that of uncoated UC-II. Moreover, incorporating Cur into the UC-II/SA nanofibrils resulted in a 300 times increase in Cur solubility and showcased the superior dispersion stability, antioxidant activity, and sustained release profile during simulated digestion. These findings underscored the dual functionality of the UC-II/SA system as both a stabilizing agent for UC-II nanofibrils and an efficient carrier for Cur delivery.

Physicochemical and Functional Properties of Thermal-Induced Polymerized Goat Milk Whey Protein

Goat milk whey protein products are a hard-to-source commodity. Whey protein concentrate was directly prepared from fresh goat milk. The effects of the heating temperature (69-78 °C), time (15-30 min), and pH (7.5-7.9) on the physicochemical and functional properties of the goat milk whey protein were investigated. The results showed that the particle size of the samples significantly increased (p < 0.05) after heat treatment. The zeta potential of polymerized goat milk whey protein (PGWP) was lower than that of native goat milk whey protein. The content of the free sulfhydryl groups of PGWP decreased with increasing heating temperature and time, while an increase in surface hydrophobicity and apparent viscosity of PGWP were observed after heat treatment. Fourier Transform Infrared Spectroscopy analysis indicated that heat treatment and pH had considerable impacts on the secondary structure of goat milk whey protein. Transmission electron microscope images revealed that heat induced the formation of a large and uniform protein network. Additionally, the changes in the physicochemical and structural properties contributed to the improvement of the emulsifying and foaming properties of goat milk whey protein after heat treatment. The results may provide a theoretical basis for the applications of polymerized goat milk whey protein in related products.

Caffeine-loaded nano/micro-carriers: Techniques, bioavailability, and applications

Caffeine, as one of the most consumed bioactive compounds globally, has gained considerable attention during the last years. Considering the bitter taste and adverse effects of high levels of caffeine consumption, it is crucial to apply a strategy for masking the caffeine's bitter taste and facilitating its programmable deliverance within a long time. Other operational parameters such as food processing parameters, exposure to sunlight and oxygen, and gastrointestinal digestion could also degrade the phenolic compounds in general and caffeine in special. To overcome these challenges, various nano/micro-platforms have been fabricated, including lipid-based (e.g., nanoliposomal vehicles; nanoemulsions, double emulsions, Pickering emulsions; microemulsions; niosomal vehicles; solid lipid nanoparticles and nanostructured lipid carriers), as well as biopolymeric (e.g., nanoparticles; hydrogels, organogels, oleogels; nanofibers and nanotubes; protein-polysaccharide nanocomplexes, conjugates; cyclodextrin inclusion complexes) and inorganic (e.g., gold and silica nanoparticles) nano/micro-structures. In this review, the findings on various caffeine-loaded nano/micro-carriers and their potential applications in functional food products/supplements will be discussed. Also, the controlled release and bioavailability of encapsulated caffeine will be given, and finally, the toxicity and safety of encapsulated caffeine will be presented.

Microfluidics-based production of chitosan-gellan nanocomplexes encapsulating caffeine

Electrostatic complexes produced by interactions between polysaccharides have promising applications in the medical, pharmaceutical and food fields. In this light, for the development of such particles, microfluidics emerges as a promising technique in which processes occur at a strict laminar flow regime, allowing diffusion-dominated transport and particle formation in highly-controlled conditions. As a proof of concept, we compared bulk versus microfluidic (different devices simulating a range of residence times) processes for the production of electrostatic complexes of gellan with either chitosan (molecular weight ∼ 28 kDa) or hydrolyzed chitosan (molecular weight ∼ 3 kDa). Regardless of the process, polysaccharide solutions (pH 4.5) were mixed in pre-defined concentrations (polysaccharide ratios) to form electrostatic complexes that were used to encapsulate caffeine. These complexes were characterized by zeta potential measurements and particle size distribution. Overall, microfluidics produced complexes with improved characteristics such as lower polydispersity index (PDI ∼ 0.1) and mean size (∼200 nm) when compared to the conventional bulk process (PDI ∼ 0.3 and mean size ∼ 400 nm). Moreover, hydrolyzed chitosan (HC) contributed to an even smaller size and PDI value of the complexes. Such outcome is associated with the lower molecular weight and higher solubility of HC when comparing to conventional chitosan, which in turn improves electrostatic complexation. Caffeine could also be encapsulated in all complexes, but the highest encapsulation efficiency was achieved using microfluidics (70%) and with the geometry that provided a longer residence time. Therefore, we were able to demonstrate that microfluidics is clearly an effective strategy for generating electrostatic complexes with improved properties. Ultimately, this technique demonstrated a high potential for the production of vehicles of bioactive compounds.

Development of Encapsulation Strategies and Composite Edible Films to Maintain Lactoferrin Bioactivity: A Review

Lactoferrin (LF) is a whey protein with various and valuable biological activities. For this reason, LF has been used as a supplement in formula milk and functional products. However, it must be considered that the properties of LF can be affected by technological treatments and gastrointestinal conditions. In this article, we have revised the literature published on the research done during the last decades on the development of various technologies, such as encapsulation or composite materials, to protect LF and avoid its degradation. Multiple compounds can be used to conduct this protective function, such as proteins, including those from milk, or polysaccharides, like alginate or chitosan. Furthermore, LF can be used as a component in complexes, nanoparticles, hydrogels and emulsions, to encapsulate, protect and deliver other bioactive compounds, such as essential oils or probiotics. Additionally, LF can be part of systems to deliver drugs or to apply certain therapies to target cells expressing LF receptors. These systems also allow improving the detection of gliomas and have also been used for treating some pathologies, such as different types of tumours. Finally, the application of LF in edible and active films can be effective against some contaminants and limit the increase of the natural microbiota present in meat, for example, becoming one of the most interesting research topics in food technology.

In vitro Digestion and Swelling Kinetics of Thymoquinone-Loaded Pickering Emulsions Incorporated in Alginate-Chitosan Hydrogel Beads

The present work aimed to investigate the swelling behavior, in vitro digestion, and release of a hydrophobic bioactive compound, thymoquinone (TQ), loaded in Pickering emulsion incorporated in alginate-chitosan hydrogel beads using a simulated gastrointestinal model. In this study, oil-in-water Pickering emulsions of uniform micron droplet sizes were formulated using 20% red palm olein and 0.5% (w/v) cellulose nanocrystals-soy protein isolate (CNC/SPI) complex followed by encapsulation within beads. FT-IR was used to characterize the bonding between the alginate, chitosan, and Pickering emulsion. 2% (w/v) alginate-1% (w/v) chitosan hydrogel beads were found to be spherical with higher stability against structural deformation. The alginate-chitosan beads displayed excellent stability in simulated gastric fluid (SGF) with a low water uptake of ~19%. The hydrogel beads demonstrated a high swelling degree (85%) with a superior water uptake capacity of ~593% during intestinal digestion in simulated intestinal fluid (SIF). After exposure to SIF, the microstructure transformation was observed, causing erosion and degradation of alginate/chitosan wall materials. The release profile of TQ up to 83% was achieved in intestinal digestion, and the release behavior was dominated by diffusion via the bead swelling process. These results provided useful insight into the design of food-grade colloidal delivery systems using protein-polysaccharide complex-stabilized Pickering emulsions incorporated in alginate-chitosan hydrogel beads.

Molecular forces governing protein-protein interaction: Structure-function relationship of complexes protein in the food industry

The application of protein-protein interaction (PPI) has been widely used in various industries, such as food, nutraceutical, and pharmaceutical. A deeper understanding of PPI is needed, and the molecular forces governing proteins and their interaction must be explained. The design of new structures with improved functional properties, e.g., solubility, emulsion, and gelation, has been fueled by the development of structural and colloidal building blocks. In this review, the molecular forces of protein structures are discussed, followed by the relationship between molecular force and structure, ways of a bind of proteins together in solution or at the interface, and functional properties. A more detailed look is thus taken at the relationship between the various influencing factors on molecular forces involved in PPI. These factors include protein properties, such as types, concentration, and mixing ratio, and solvent conditions, such as ionic strength and pH. This review also summarizes methods tha1t are capable of identifying molecular forces in protein and PPI, as well as characterizing protein structure.

Physicochemical and emulsifying properties of mussel water-soluble proteins as affected by lecithin concentration

The effects of lecithin addition at different concentrations (0-2.0%) on the physicochemical and emulsifying properties of mussel water-soluble proteins (MWP) were investigated. In solution system, low lecithin concentration (0.5%-1.0%) induced the aggregation and increased turbidity of composite particles. Lecithin addition caused changes in secondary structure and induced partial unfolding of MWP. Hydrophobic interactions between MWP and lecithin may contribute to the exposure of chromophores and hydrophobic groups of MWP. The interfacial tension decreased with lecithin addition. However, at a high lecithin concentration (1.5%-2.0%), the degree of aggregation and state of unfolding alleviated due to competitive adsorption. In emulsion system, with the low concentration of lecithin addition (0.5%-1.0%), droplet size and surface charge of emulsion decreased. The emulsion activity index, emulsion stability index, percentage of adsorbed protein increased. Both creaming stability and viscoelastic properties improved. At an intermediate lecithin concentration (1.0%), the emulsion showed the highest physical stability, while further addition of lecithin caused a slight deterioration in emulsifying properties. Overall, these results indicated the possibility that the lecithin-MWP mixed emulsifiers can be used to obtain emulsions with desirable properties.

N-Acetyl-l-cysteine/l-Cysteine-Functionalized Chitosan-β-Lactoglobulin Self-Assembly Nanoparticles: A Promising Way for Oral Delivery of Hydrophilic and Hydrophobic Bioactive Compounds

Self-assembled and cross-linked hybrid hydrogels for entrapment and delivery of hydrophilic and hydrophobic bioactive compounds were developed based on N-acetyl-l-cysteine (NAC)- or l-cysteine (CYS)-functionalized chitosan-β-lactoglobulin nanoparticles (NPs). In both the systems, amphiphilic protein β-lactoglobulin (β-lg) was self-assembled by using glutaraldehyde for affinity binding with egg white-derived peptides (EWDP) and curcumin and then coated with NAC- or CYS-functionalized chitosan (CS) by electrostatic interaction. The resulting NPs were characterized in terms of size, polydispersity, and surface charge by dynamic light scattering. Results corroborated pH-sensitive properties of NAC-CS-β-lg NPs and CYS-CS-β-lg NPs with the particle size as small as 118 and 48 nm, respectively. The two kinds of NPs also showed excellent entrapment of EWDP and curcumin with the entrapment efficiency (EE) of EWDP and curcumin ranging from 51 to 89% and 42 to 57% in NAC-CS-β-lg NPs, as well as 50-81% and 41-57% in CYS-CS-β-lg NPs under different pH values. Fourier transform infrared and molecular docking studies provided support for the interaction mechanism of NAC/CYS-CS with β-lg as well as the NPs with EWDP and curcumin. Strikingly, the in vitro release kinetics of EWDP and curcumin exhibited the controlled and sustained release properties up to 58 and 70 h from the NPs, respectively. Note that the permeability of QIGLF (pentapeptide, isolated from EWDP) and curcumin passing through Caco-2 cell monolayers were all improved after the entrapment in the NPs. This work offers promising methods for effective entrapment and oral delivery of both hydrophilic and hydrophobic bioactive compounds.

Comparison of dry- and wet-heat induced changes in physicochemical properties of whey protein in absence or presence of inulin

Changes in whey protein (10%, w/v) induced by dry-heating (60 °C for 5 days at a relative humidity of 63%), wet-heating (85 °C for 30 min) or the two-combined heating in absence or presence of inulin (8%, w/v) were studied. Mixture of whey protein and inulin showed significantly higher absorbance at 290 nm than whey protein alone in all heating conditions while only dry-heated samples showed significantly increased absorbance value at 420 nm (p < 0.05). Whey protein after heating showed significantly lower zeta potential and inulin decreased the value of all heated samples further (p < 0.05) except for samples after dry-heating. Heating decreased the free sulfhydryl group content of whey protein samples while presence of inulin decreased further (p < 0.05). Dry-heating decreased while wet-heating increased the surface hydrophobicity of whey protein. Inulin had no effect on the surface hydrophobicity of heated whey protein under dry-heating but decreased under wet-heating.

Protein-Based Nanostructures for Food Applications

Proteins are receiving significant attention for the production of structures for the encapsulation of active compounds, aimed at their use in food products. Proteins are one of the most used biomaterials in the food industry due to their nutritional value, non-toxicity, biodegradability, and ability to create new textures, in particular, their ability to form gel particles that can go from macro- to nanoscale. This review points out the different techniques to obtain protein-based nanostructures and their use to encapsulate and release bioactive compounds, while also presenting some examples of food grade proteins, the mechanism of formation of the nanostructures, and the behavior under different conditions, such as in the gastrointestinal tract.

Systematical characterization of physiochemical and rheological properties of thermal-induced polymerized whey protein

BACKGROUND

Effects of pH (6-8), protein concentration (60-110, g kg^-1 ), heating temperature (70-95 °C) and time (5-30 min) on physiochemical and rheological properties of thermal-induced polymerized whey protein isolate (PWP) were systematically investigated. Degree of denaturation, particle size, zeta potential, free sulfhydryl group content, surface hydrophobicity and apparent viscosity were determined.

RESULTS

Heating whey protein above 75 °C at pH 7 or 8 resulted in denaturation of 80-90% whey protein. pH variation had a remarkable influence on particle size of samples (P < 0.05), whereas heating temperature and time did not generate significant changes. Zeta potential of PWP samples fell in the range of -30 to -40 mV. Free sulfhydryl group content of PWP samples decreased with increasing level regarding each factor. Surface hydrophobicity analysis showed that samples at higher pH or concentration became less hydrophobic, and increasing heating temperature or time resulted in higher hydrophobicity index. Time sweep test revealed that increasing protein concentration, heating temperature or time led to higher apparent viscosity. Flow behavior of PWP samples approached Newtonian character as protein concentration, heating temperature or time decreased.

CONCLUSION

Systematic data may provide helpful information in designing a heating process for dairy products and application of PWP in the food industry. © 2018 Society of Chemical Industry.

Interactions between whey protein or polymerized whey protein and soybean lecithin in model system

Soybean lecithin is often used as a surfactant in food formulation. The aim of this study was to investigate the interactions between soybean lecithin (SL, 0-3%, wt/vol) and whey protein (WP, 10%, wt/vol) or polymerized whey protein (PWP, 10%, wt/vol) induced by heating WP solutions at 85°C for 0 to 20 min at pH 7.0. The samples were evaluated for zeta potential, particle size, morphology, rheological properties, thermal properties, secondary structure, and surface hydrophobicity. Zeta potential of WP increased linearly as SL level increased from 0 to 3%, whereas that of PWP changed with plateau at SL level of 1%, which may be due to the aggregation of SL. The addition of SL increased the particle size and apparent viscosity of both WP and PWP. All the samples exhibited different morphology depending on SL level and heating time according to transmission electron microscopy images. Whey protein showed obviously decreased gelation time and increased storage modulus in the presence of SL. Differential scanning calorimetry curves confirmed the effects of SL on the thermal properties of both WP and PWP. Circular dichroism spectra indicated that SL had effects on the secondary structure of both WP and PWP. The changes in surface hydrophobicity indicated the hydrophobic interactions between WP/PWP and SL. Data indicate that the physicochemical and functional properties of WP and PWP can be altered by adding soybean lecithin.

Interactions between whey protein and inulin in a model system

Inulin is a commonly used prebiotic ingredients for functional food formulation. The effect of inulin on the gelation properties of whey protein was investigated using whey protein and inulin (WP/inulin) and polymerized whey protein and inulin (PWP/inulin) mixtures at different levels of protein (4-8%, w/v) and inulin (1-5%, w/v). WP/inulin mixture was prepared by heating protein and inulin together while the latter by heating protein alone and then mixed with inulin. Both mixtures were analyzed for turbidity, zeta potential, particle size, and rheological properties. Dispersions became more opaque with increasing protein but there was no significant difference between the two mixtures. A small shift towards larger size and significantly decreased negative zeta potential with increasing inulin addition (1-5%) were observed for both mixtures. WP/PWP and inulin mixtures exhibited a shear thinning behavior. Transition temperature of whey protein increased with inulin addition. WP/PWP and inulin mixtures were induced into cold-set gels by calcium and the gels were analyzed for hardness. Hardness of WP/PWP and inulin gels increased with the increasing inulin. Results indicated that interactions between whey protein and inulin had impact on the gelation properties of whey protein regardless the way inulin added.

Effects of UV-B radiation on the isoflavone accumulation and physiological-biochemical changes of soybean during germination: Physiological-biochemical change of germinated soybean induced by UV-B

In this study, the effects of UV-B radiation on the isoflavones accumulation, physiological and nutritional quality, water status, and characteristics of proteins in germinated soybeans were investigated. The results showed that isoflavones content in soybeans increased with appropriate intensity and time of UV-B radiation and decreased with excessive treatment. Fresh weight, length, free amino acids, reducing sugar contents and bulk water (T23) in germinated soybeans decreased with increasing radiation time, indicating that UV-B inhibited the growth and nutrients metabolism of soybean during germination. Cell damage was detected in germinated soybeans with excessive UV-B radiation, as shown by the black spots in cotyledons and the increased intercellular water determined by LF-NMR. Germination resulted in an increase in random coil structures, while UV-B radiation induced no obvious changes in FT-IR spectrum and protein conformation of soybeans. Both UV-B radiation and germination caused the increase in soluble proteins, especially in 1.0-75.0 kDa fraction.

Micro- and nano bio-based delivery systems for food applications: In vitro behavior

Micro- and nanoencapsulation is an emerging technology in the food field that potentially allows the improvement of food quality and human health. Bio-based delivery systems of bioactive compounds have a wide variety of morphologies that influence their stability and functional performance. The incorporation of bioactive compounds in food products using micro- and nano-delivery systems may offer extra health benefits, beyond basic nutrition, once their encapsulation may provide protection against undesired environmental conditions (e.g., heat, light and oxygen) along the food chain (including processing and storage), thus improving their bioavailability, while enabling their controlled release and target delivery. This review provides an overview of the bio-based materials currently used for encapsulation of bioactive compounds intended for food applications, as well as the main production techniques employed in the development of micro- and nanosystems. The behavior of such systems and of bioactive compounds entrapped into, throughout in vitro gastrointestinal systems, is also tracked in a critical manner. Comparisons between various in vitro digestion systems (including the main advantages and disadvantages) currently in use, as well as correlations between the behavior of micro- and nanosystems studied through in vitro and in vivo systems were highlighted and discussed here for the first time. Finally, examples of bioactive micro- and nanosystems added to food simulants or to real food matrices are provided, together with a revision of the main challenges for their safe commercialization, the regulatory issues involved and the main legislation aspects.