Micellization of casein-graft-dextran copolymer prepared through Maillard reaction

A Novel Method for the Preparation of Casein-Fucoidan Composite Nanostructures

The aim of the study was to develop casein-fucoidan composite nanostructures through the method of polyelectrolyte complexation and subsequent spray drying. To determine the optimal parameters for the preparation of the composite structures and to investigate the influence of the production and technological parameters on the main structural and morphological characteristics of the obtained structures, 3(k-p) fractional factorial design was applied. The independent variables (casein to fucoidan ratio, glutaraldehyde concentration, and spray intensity) were varied at three levels (low, medium, and high) and their effect on the yield, the average particle size, and the zeta potential were evaluated statistically. Based on the obtained results, models C1F1G1Sp.30, C1F1G2Sp.40, and C1F1G3Sp.50, which have an average particle size ranging from (0.265 ± 0.03) µm to (0.357 ± 0.02) µm, a production yield in the range (48.9 ± 2.9) % to (66.4 ± 2.2) %, and a zeta potential varying from (-20.12 ± 0.9) mV to (-25.71 ± 1.0) mV, were selected as optimal for further use as drug delivery systems.

Casein-based conjugates and graft copolymers. Synthesis, properties, and applications

Biobased natural polymers, including polymers of natural origin such as casein, are growing rapidly in the light of the environmental pollution caused by many mass-produced commercial synthetic polymers. Although casein has interesting intrinsic properties, especially for the food industry, numerous chemical reactions have been carried out to broaden the range of its properties, most of them preserving casein's nontoxicity and biodegradability. New conjugates and graft copolymers have been developed especially by Maillard reaction of the amine functions of the casein backbone with the aldehyde functions of sugars, polysaccharides, or other molecules. Carried out with dialdehydes, these reactions lead to the cross-linking of casein giving three-dimensional polymers. Acylation and polymerization of various monomers initiated by amine functions are also described. Other reactions, far less numerous, involve alcohol and carboxylic acid functions in casein. This review provides an overview of casein-based conjugates and graft copolymers, their properties, and potential applications.

1-Amino-1-deoxy-d-fructose ("fructosamine") and its derivatives

Fructosamine has long been considered as a key intermediate of the Maillard reaction, which to a large extent is responsible for specific aroma, taste, and color formation in thermally processed or dehydrated foods. Since the 1980s, however, as a product of the Amadori rearrangement reaction between glucose and biologically significant amines such as proteins, fructosamine has experienced a boom in biomedical research, mainly due to its relevance to pathologies in diabetes and aging. In this chapter, we assess the scope of the knowledge on and applications of fructosamine-related molecules in chemistry, food, and health sciences, as reflected mostly in publications within the past decade. Methods of fructosamine synthesis and analysis, its chemical, and biological properties, and degradation reactions, together with fructosamine-modifying and -recognizing proteins are surveyed.

Chemical modification of edible sodium caseinate: A new grafting method of oleic acid. Characterization and thermal properties of the conjugate

Sodium caseinate is a well-known amphiphilic protein derived from natural products currently used for the preparation of edible films. To improve some properties, especially to decrease the hydrophilicity and water solubility of the caseinate, the covalent grafting of a hydrophobic edible fatty acid, namely oleic acid, onto caseinate, appears to be a solution. We describe a new synthesis method for the chemical modification of sodium caseinate involving the synthesis of an acid chloride derivative from oleic acid and a phase transfer catalysis reaction in a biphasic medium. Under these conditions, free amine and alcohol groups of the caseinate are likely to be grafted with a fairly high (>50 %) substitution degree. The caseinate derivative is finely characterized, in particular by DOSY NMR, to assess the formation of a casein/oleic acid grafted compound as well as the absence of residual oleic acid.

Glucose-Modified Zein Nanoparticles Enhance Oral Delivery of Docetaxel

Based on glucose (G) transporters (GLUTs), structuring nanoparticles with G as a target are an effective strategy to enhance oral bioavailability and anti-tumor effects of drugs. A novel drug delivery system using G-modified zein (GZ) nanoparticles loaded with docetaxel (DTX) (DTX-GNPs) was prepared and characterized in vitro and in vivo via assessment of cellular uptake, absorption site, pharmacokinetics, ex vivo distribution, and anti-tumor effects. The DTX-GNPs were approximately 120 nm in size. Compared with DTX-NPs, G modification significantly enhanced cellular uptake of DTX-GNPs by 1.22 times in CaCo-2 cells, which was related to GLUT mediation and the enhancement of endocytosis pathways via clathrin, micropinocytosis, and caveolin. Compared to DTX-NPs, G modification significantly enhanced DTX-NP absorption in the jejunum and ileum, delayed plasma concentration peak time, prolonged the average residence time in vivo, and increased oral bioavailability (from 43.82% to 96.04%). Cellular uptake and oral bioavailability of DTX were significantly affected by the G modification ratio. Compared with DTX-NPs, G modification significantly reduced drug distribution in the liver, lungs, and kidneys and increased tumor distribution and tumor growth inhibition rate without obvious systemic toxicity. This study demonstrated the potential of GZ-NPs as nanocarriers for DTX to enhance oral bioavailability and anti-tumor effects.

Protein-polysaccharide interactions for the fabrication of bioactive-loaded nanocarriers: Chemical conjugates and physical complexes

As unique biopolymeric architectures, covalently and electrostatically protein-polysaccharide (PRO-POL) systems can be utilized for bioactive delivery by virtue of their featured structures and unique physicochemical attributes. PRO-POL systems (i. e, microscopic /nano-dimensional multipolymer particles, molecularly conjugated vehicles, hydrogels/nanogels/oleogels/emulgels, biofunctional films, multilayer emulsion-based delivery systems, particles for Pickering emulsions, and multilayer coated liposomal nanocarriers) possess a number of outstanding attributes, like biocompatibility, biodegradability, and bioavailability with low toxicity that qualify them as powerful agents for the delivery of different bioactive ingredients. To take benefits from these systems, an in-depth understanding of the chemical conjugates and physical complexes of the PRO-POL systems is crucial. In this review, we offer a comprehensive study concerning the unique properties of covalently/electrostatically PRO-POL systems and introduce emerging platforms to fabricate relevant nanocarriers for encapsulation of bioactive components along with a subsequent sustained/controlled release.

Formation of colloidal micro-nano particles and flavor characteristics of Greenland halibut bone soup

In this study, halibut bone, a byproduct of Greenland halibut processing, was prepared into a thick soup through a non-frying process. The formation of colloidal micro-nano particles and flavor characteristics in halibut bone soup was explored. The results showed that the nutrients in halibut bones migrated to the soup continuously with the cooking process and reached the highest concentration (total sugars, 38.16 mg/100 ml; water-soluble proteins, 25.71 mg/ml; fatty acids, 2.15 g/100 ml; solids, 1.14 g/100 ml) at 150 min. Taste substances such as organic acids, 5'-nucleotides and total free amino acids (TFAAs) content in halibut bone soup also reached maximum at 150 min. At this time, results for particle size showed that MNPs with uniform size (725.62 nm) were formed, which made the bone soup milky white, stable, and had good tasting. Headspace-gas chromatography-ion mobility spectrometry results showed that a total of 59 volatile substances were detected from the halibut bone soup. The content of volatile flavor substances in the 150 min group was lower than that in the 90-120 min group. Meanwhile, aldehydes and ketones gradually became esters. PRACTICAL APPLICATION: Soup is an indispensable part of the world food culture. In order to increase the added value of Greenland halibut, halibut bone soup was studied in this paper. This study found that halibut bone soup that had not been fried, formed the MNPs and has a more harmonious and pleasant flavor. Thus, non-fried halibut bone soup is a good processing method and can improve economic efficiency.

Insulin- and cholic acid-loaded zein/casein-dextran nanoparticles enhance the oral absorption and hypoglycemic effect of insulin

Diabetes mellitus is the most common metabolic disease in the world. Herein, insulin- and cholic acid-loaded zein nanoparticles with dextran surfaces were fabricated to enhance the oral absorptions of insulin in the intestine and in the liver which is the primary action organ of endogenous insulin. In the nanoparticles, zein acted as cement to embed insulin, cholic acid and casein by hydrophobic interactions. The hydrophilic dextran conjugated to casein by the Maillard reaction was located on the nanoparticle surface. The nanoparticles had an insulin loading efficiency of 74.6%, a cholic acid loading efficiency of 55.1% and a hydrodynamic diameter of 267 nm. The dextran significantly increased the disperse stability of the nanoparticles, protected the loaded insulin from hydrolysis in digestive juices, and increased the trans-mucus permeability of the insulin. The embedded cholic acid molecules were consecutively exposed to the surface when the nanoparticles were gradually eroded by proteases. The exposed cholic acid promoted the absorptions of the nanoparticles in the ileum and liver via bile acid transporters. The effect of pretreated lymphatic transport inhibitor cycloheximide revealed that about half of the nanoparticles were transported via the intestinal lymphatic transport pathway and the other half of the nanoparticles were transported via portal blood absorption. The oral pharmacological bioavailability of the nanoparticles in type I diabetic mice was 12.5-20.5%. This study demonstrates that nanoparticles are a promising oral delivery system for insulin.

Formation of a novel coating material containing lutein and zeaxanthin via a Maillard reaction between bovine serum albumin and fucoidan

The effective delivery of bioactive compounds has recently been receiving attention. In this study, a conjugate with BSA and fucoidan synthesized via the Maillard reaction was confirmed through electrophoresis, the o-phthalaldehyde assay, and through changes in absorbance. Two moles of fucoidan were glycated with one mole of BSA at 60 °C and 79% relative humidity for 4 days. The droplet coated with B-F conjugate remained stable during storage at 4 and 25 °C and slightly increased only at 55 °C however, the droplet coated with intact BSA and B/F mixture significantly increased. L/Z were degraded about 82, 79, and 36% for 4, 25, and 55 °C, respectively, regardless of the type of emulsifier. Although the conjugates could not prevent the degradation of lutein and zeaxanthin during storage, they improved the stability of the emulsion and showed 4.20-fold and 1.32-fold higher bioaccessibility than intact BSA and B/F mixtures, respectively.

Zein-Polyglycerol Conjugates with Enhanced Water Solubility and Stabilization of High Oil Loading Emulsion

To increase the water solubility of zein as a stabilizing agent for oil-in-water (O/W) emulsions, three zein-polyglycerol (Zein-PG) conjugates, Zein-PG-2, Zein-PG-6, and Zein-PG-10, were prepared by dehydration between zein and polyglycerol aldehydes obtained by NaIO₄ oxidation of polyglycerol-2, -6, and -10 and characterized by free amine content, grafting degree, Fourier transform infrared spectroscopy, and fluorescence spectra. All conjugates dispersed in water as nanoparticles were verified by transmission electron microscopy. Conjugation with PG changed the isoelectric point of zein from 6.2 to 6.8 and to 4.0. Zein-PG-6 and Zein-PG-10 showed strong stabilization on the O/W emulsions with 18-fold loading of soybean oil on the basis of conjugate mass, displaying high oil loading capacity. Confocal laser scanning microscopy (CLSM) confirmed the O/W structure of emulsions and that the absorption of Zein-PG-10 on the oil droplet surface offered the driving force to be stable. The present Zein-PG conjugates thus produced an enticing resource for use as nanocarriers or bioemulsifiers in food or pharmaceutical industries.

Preparation and potential applications of casein-polysaccharide conjugates: a review

Glycation of casein and caseinates with polysaccharides via Maillard reaction is a simple and environmentally safe way to prepare new food ingredients of improved functional properties. Sodium caseinate has been used mainly to prepare conjugates with several polysaccharides particularly maltodextrins and dextrans. The functional properties of these conjugates are influenced by the used polysaccharides and heating conditions. Under optimal heating conditions substantial improvements have been evident in their emulsification and foam properties of these conjugates. Casein-polysaccharide conjugates have several potential applications in food processing and microencapsulation. This article gives an overview on their formation and potential uses. © 2019 Society of Chemical Industry.

Encapsulation of Lutein in Nanoemulsions Stabilized by Resveratrol and Maillard Conjugates

Lutein is incorporated into foods as a natural yellow pigment and nutraceutical. The introduction of lutein into many foods and beverages, however, is problematic because of its strong hydrophobicity and poor chemical stability. In this research, lutein-loaded nanoemulsions were prepared to overcome this problem. Casein-dextran Maillard conjugates or physical complexes were utilized as emulsifiers, while either medium chain triglycerides (MCT) or grape seed oil (GSO) were used as carrier oils. The impact of resveratrol addition on nanoemulsion stability was also examined. The influence of storage temperature, pH, and CaCl₂ concentration on the chemical and physical stability of the nanoemulsions was measured. The casein-dextran conjugates were highly effective at improving the physical resistance of the nanoemulsions to environmental stresses, but had a detrimental effect on their color stability. Conversely, nanoemulsions prepared from casein-dextran physical complexes were unstable around the protein's isoelectric point (pH 4.6), as well as upon addition of CaCl₂ . Incorporation of resveratrol and GSO into the nanoemulsions decreased lutein degradation and color fading at all temperatures. This study shows that casein-dextran conjugates are highly effective at improving the physical stability of lutein-loaded nanoemulsions, while resveratrol and GSO are effective at improving their chemical stability. PRACTICAL APPLICATION: Lutein can be used by the food industry to create "clean label" and functional food products. The major challenges in incorporating lutein in foods are its poor chemical stability and its high hydrophobicity, which makes it difficult to incorporate. Emulsion-based delivery systems assembled from natural ingredients may address these challenges. In this study, the impact of Maillard conjugates fabricated from caseinate and dextran, as well as resveratrol addition, on the formation and stability of lutein-enriched nanoemulsions was determined. The information obtained from this study will help the formulation of more effective functional foods and beverage products.

Protein-polysaccharide nanohybrids: Hybridization techniques and drug delivery applications

Complex nanosystems fabricated by hybridization of different types of materials such as lipids, proteins, or polysaccharides are usually superior to simple ones in terms of features and applications. Proteins and polysaccharides hold great potential for development of nanocarriers for drug delivery purposes based on their unique biocompatibility, biodegradability, ease of functionalization, improved biodistribution and minimal toxicity profiles. Protein-polysaccharide nanohybrids have gained a lot of attention in the past few years particularly for drug delivery applications. In this review, different hybridization techniques utilized in the fabrication of such nanohybrids including electrostatic complexation, Maillard conjugation, chemical coupling and electrospinning were thoroughly reviewed. Moreover, various formulation factors affecting the characteristics of the formed nanohybrids were discussed. We also reviewed in depth the outcomes of such hybridization ranging from stability enhancement, to toxicity reduction, improved biocompatibility, and drug release modulation. We also gave an insight on their limitations and what hinders their clinical translation and market introduction.

Potential of Casein as a Carrier for Biologically Active Agents

Casein is the collective name for a family of milk proteins. In bovine milk, casein comprises four peptides: α_S1, α_S2, β, and κ, differing in their amino acid, phosphorus and carbohydrate content but similar in their amphiphilic character. Hydrophilic and hydrophobic regions of casein show block distribution in the protein chain. Casein peptides carry negative charge on their surface as a result of phosphorylation and tend to bind nanoclusters of amorphous calcium phosphate. Due to these properties, in suitable conditions, casein molecules agglomerate into spherical micelles. The high content of casein in milk (2.75 %) has made it one of the most popular proteins. Novel research techniques have improved understanding of its properties, opening up new applications. However, casein is not just a dietary protein. Its properties promise new and unexpected applications in science and the pharmaceutical and functional food industries. One example is an encapsulation of health-related substances in casein matrices. This review discusses gelation, coacervation, self-assembly and reassembly of casein peptides as means of encapsulation. We highlight information on encapsulation of health-related substances such as drugs and dietary supplements inside casein micro- and nanoparticles.

Synthetic surfactant- and cross-linker-free preparation of highly stable lipid-polymer hybrid nanoparticles as potential oral delivery vehicles

The toxicity associated with concentrated synthetic surfactants and the poor stability at gastrointestinal condition are two major constraints for practical applications of solid lipid nanoparticles (SLN) as oral delivery vehicles. In this study, a synthetic surfactant-free and cross-linker-free method was developed to fabricate effective, safe, and ultra-stable lipid-polymer hybrid nanoparticles (LPN). Bovine serum albumin (BSA) and dextran varying in molecular weights were first conjugated through Maillard reaction and the conjugates were exploited to emulsify solid lipid by a solvent diffusion and sonication method. The multilayer structure was formed by self-assembly of BSA-dextran micelles to envelope solid lipid via a pH- and heating-induced facile process with simultaneous surface deposition of pectin. The efficiency of different BSA-dextran conjugates was systematically studied to prepare LPN with the smallest size, the most homogeneous distribution and the greatest stability. The molecular interactions were characterized by Fourier transform infrared and fluorescence spectroscopies. Both nano spray drying and freeze-drying methods were tested to produce spherical and uniform pectin-coated LPN powders that were able to re-assemble nanoscale structure when redispersed in water. The results demonstrated the promise of a synthetic surfactant- and cross-linker-free technique to prepare highly stable pectin-coated LPN from all natural biomaterials as potential oral delivery vehicles.

Effect of Maillard Conjugates on the Physical Stability of Zein Nanoparticles Prepared by Liquid Antisolvent Coprecipitation

Protein nanoparticles are often not very stable in a complex food matrix because they are primarily stabilized by electrostatic repulsion. In this study, we envisaged the stabilization of zein nanoparticles through Maillard conjugation reactions with polysaccharides of different molecular mass. Zein nanoparticles (0.5% w/v) containing resveratrol (0.025% w/v grape skin extract) were produced by liquid antisolvent precipitation and coated with Maillard conjugates (MC) of sodium caseinate and different molecular mass carbohydrates during particle production. Zein nanoparticles coated with conjugated polysaccharides of 2.8, 37, and 150 kDa had diameters of 198 ± 5, 176 ± 6, and 180 ± 3 nm, respectively. The encapsulation efficiency (∼83%) was not affected by conjugation, but the conjugates significantly improved particle stability against changes in pH (2.0-9.0), CaCl2 addition (up to 100 mM), and heat treatment (30-90 °C, 30 min). Zein nanoparticles coated by MC may therefore be suitable delivery systems for hydrophobic bioactive molecules in a wide range of commercial products.

Coated biodegradable casein nanospheres: a valuable tool for oral drug delivery

Biodegradable casein nanospheres for the sustained release of bioactive molecules in the gastro-intestinal tract were prepared by precipitation polymerization using sodium methacrylate (NaMA) and N,N'-methylene bis-acrylamide (MEBA) as pH-responsive monomer and cross-linker. Three materials with different casein amount were obtained and characterized by scanning electron microscopy, dimensional analysis, water uptake, cytotoxicity and enzymatic degradation experiments. Nanospheres biodegradability was tuned by coating with polyacrylic acid. Coated and uncoated materials were investigated as delivery vehicles for diclofenac sodium salt. For un-coated samples, the release raise 100% in 30 h, while for coated specimens these values were lower than 70%, due to the diffusional constraints of polymer layer.

Improving resveratrol bioaccessibility using biopolymer nanoparticles and complexes: impact of protein-carbohydrate maillard conjugation

The impact of encapsulating resveratrol in biopolymer nanoparticles or biopolymer complexes on its physicochemical stability and bioaccessibility was determined. The biopolymer nanoparticles consisted of a zein core surrounded by a caseinate or caseinate-dextran shell. The biopolymer complexes consisted of resveratrol bound to caseinate or caseinate-dextran. The caseinate-dextran conjugates were formed using the Maillard reaction. Both the biopolymer nanoparticles and complexes protected trans-resveratrol from isomerization when exposed to UV light, with the nanoparticles being more effective. Nanoparticles coated by caseinate-dextran were more stable to aggregation under simulated gastrointestinal conditions than those coated by caseinate, presumably due to greater steric repulsion. The bioaccessibility of resveratrol was enhanced when it was encapsulated in both biopolymer nanoparticles and biopolymer complexes. These results have important implications for the development of effective delivery systems for incorporating lipophilic nutraceuticals into functional foods and beverages.

Antioxidant activity of bovine alpha lactalbumin Maillard products and evaluation of their in vitro gastro-duodenal digestive proteolysis

Maillard conjugation alters alpha lactalbumin antioxidant capacity, including during in vitro digestion, with different effect in adults versus infants.

Doxorubicin and Fe3O4 loaded albumin nanoparticles with folic acid modified dextran surface for tumor diagnosis and therapy

Doxorubicin loaded albumin nanoparticles with folic acid receptor-targeted and magnetically-guided functions significantly improve tumor therapy and MRI.

Impact of the Maillard reaction on the antioxidant capacity of bovine lactoferrin

Studies raise the notion that the Maillard reaction (MR) may be harnessed to modify the antioxidant capacity of alimentary proteins. However, little is known about the impact of MR on bioactive proteins. Glucose and fructose were used as model moieties reacting with lactoferrin (LF). UV absorbance and SDS-PAGE analyses were used to monitor MR progression during 36 h of mild thermal processing (60 °C, 79% RH). FTIR and CD did not reveal changes in LF structure; However, dynamic light scattering showed MR increased mean particle sizes and sample turbidity at 3<pH<10. DPPH and FRAP antioxidant assays showed marked increases in antioxidant capacity of Maillard conjugates as a function of reaction time (12 and 36 h), protein:monosaccharide mole ratio (1:1 or 1:3) and moiety type, compared to unprocessed LF. Overall, a link between conjugates' antioxidant capacity and processing parameters is described to enable future attempts to enhance LF functionality in foods containing carbohydrates.

Maillard-conjugate based core-shell co-assemblies for nanoencapsulation of hydrophobic nutraceuticals in clear beverages

Maillard reaction based protein-polysaccharide conjugates (PPC) are typically better emulsifiers than the proteins used to form them. Such conjugates have been proposed as encapsulation agents, but their potential as nanoencapsulation agents in clear beverages has not yet been proposed. In this research we formed casein-maltodextrin (CN-MD) conjugates and co-assembled them with hydrophobic nutraceuticals to create nanovehicles for the enrichment of clear beverages. Conjugation was validated using gel electrophoresis and by ortho-phthaldialdehyde (OPA) assay. Vitamin D (VD) was nano-entrapped by the conjugates, and compared to controls based on an unconjugated CN-MD mixture and unencapsulated VD. The following advantages of the conjugates were shown: the diameters of conjugate-VD nanoparticles was smaller and their solution was more transparent than that of the vitamin dispersion or the protein-polysaccharide mixture with VD. Conjugates conferred better protection against oxidation to both VD and epigallocatechin gallate (EGCG) than the CN-MD mixture. Conjugates were more colloidally stable at the CN original pI, allowing the formation of nanoparticles with mean diameter below 30 nm when mixed with VD, even at the original pI of CN. Conjugates provided protection against degradation at low pH and during shelf life. Entrapment efficiency was measured using Nile red (NR), a fluorescent model for a hydrophobic nutraceutical. Protein affinity to the hydrophobic compound was not diminished due to conjugation, and 90% entrapment efficiency was obtained under the conditions tested. During simulated gastric digestion, Nile red was not released from the conjugates, suggesting potential application in enteric delivery.

Active transport of oil droplets along oriented microtubules by kinesin molecular motors

We demonstrate the active transport of liquid cargos in the form of oil-in-water emulsion droplets loaded on kinesin motor proteins moving along oriented microtubules. We analyze the motility properties of the kinesin motors (velocity and run length) and find that the liquid cargo in the form of oil droplets does not alter the motor function of the kinesin molecules. This work provides a novel method for handling only a few molecules/particles encapsulated inside the oil droplets and represents a key finding for the integration of kinesin-based active transport into nanoscale lab-on-a-chip devices. We also investigate the effect of the diameter of the droplets on the motility properties of the kinesin motors. The velocity is approximately constant irrespective of the diameter of the droplets whereas we highlight a strong increase of the run length when the diameter of the droplets increases. We correlate these results with the number of kinesin motors involved in the transport process and find an excellent agreement between our experimental result and a theoretical model.

Effects of casein, ovalbumin, and dextran on the astringency of tea polyphenols determined by quartz crystal microbalance with dissipation

Tea polyphenols (TPPs) can bind with proteins and peptides through hydrophobic interaction and hydrogen bonding. Casein, ovalbumin, and dextran were used to investigate their influence on the interactions between TPP and gelatin and, therefore, to investigate their influence on TPP taste. Casein-g-dextran (CgD) and ovalbumin-g-dextran (OgD) grafting conjugates were prepared through the Maillard reaction. Dispersible CgD/OgD-TPP complexes formed in acidic pH solution even after a heating process. At the same weight ratio of protein to TPP, about 20-30% of TPP was bound to the proteins. TPP affinity for dextran is much lower. Gelatin, a model of the salivary proteins in buccal cavity, was immobilized on quartz crystal sensor surface through covalent bond. By use of a quartz crystal microbalance with dissipation, we found that the complexation of TPP with gelatin causes a dehydration and collapse of the gelatin layer on the sensor surface that is similar to the sensation of dryness and constriction on oral membranes caused by polyphenols. The complexation between TPP and casein/ovalbumin/dextran can decrease the interaction between TPP and gelatin by decreasing the free TPP molecules and shielding gelatin surface from TPP. Casein has stronger binding ability on the gelatin surface compared to ovalbumin and dextran, and therefore casein is more effective to decrease the sensation of astringency caused by TPP.

Surface hydrophobicity of physicochemically and enzymatically treated milk proteins in relation to techno-functional properties

Surface hydrophobicity (SH) of milk proteins treated physicochemically (by heating and Maillard reaction) or modified enzymatically (by transglutaminase, lactoperoxidase, laccase, and glucose oxidase) was assessed in relation to their techno-functional properties. Heat-treatment increased SH of whey protein isolate and decreased SH of sodium caseinate and bovine serum albumin. Maillard reaction of milk proteins caused time-depended decreases of SH. Only for total milk protein reacting with glucose and lactose elevated SH-values were detected. Protein modification with transglutaminase, laccase, and lactoperoxidase strongly increased the SH of whey protein isolate and total milk protein. Incubation with glucose oxidase elevated SH values of sodium caseinate, whey protein isolate, and total milk protein. When correlating SH with techno-functional properties, a positive correlation was observed between SH and foam formation, and a negative correlation was observed between SH and foam stability as well as emulsion stability. No clear correlation was detected between SH and emulsifying activity, surface tension, viscosity, and heat stability of enzymatically and physicochemically treated milk proteins.

Simultaneous nanoparticle formation and encapsulation driven by hydrophobic interaction of casein-graft-dextran and β-carotene

Casein-graft-dextran copolymer was produced using the Maillard reaction. The copolymer is molecularly soluble in neutral aqueous solution whereas beta-carotene is extremely insoluble. By the method of dialysis or evaporation then dispersing in water, the solubility of hydrophobic complex of casein and beta-carotene decreases whereas the solubility of dextran increases gradually, then nanoparticles formed with casein and beta-carotene core and dextran shell. The particles have spherical shape and are stable in aqueous solution against dilution, pH change, ionic strength change, FeCl3 oxidation and long time storage. The encapsulated beta-carotene can be released by pepsin or trypsin hydrolysis. To our knowledge, this is the first report of simultaneous nanoparticle formation and encapsulation induced by hydrophobic interaction. Casein-graft-dextran copolymer and the nanoparticle preparation is a green process in which only alkali and ethanol, no other chemicals, were used.

Micelle formation and drug release behavior of polypeptide graft copolymer and its mixture with polypeptide block copolymer

Self-association behavior of polypeptide graft copolymer and its mixture with polypeptide block copolymer and drug carrier capability of the formed micelles was examined. The results gained through fluorescence spectroscopy, transmission electron microscopy and nuclear magnetic resonance spectroscopy revealed that both polypeptide graft copolymer and its mixture with polypeptide block copolymer can self-assemble to form polymeric micelles in aqueous media. The molecular structure of the graft copolymer and blending the graft with block copolymer exert marked effects on the critical micelle concentration and the shape of formed micelles. It was found that the hydrophobic inner core of the micelles formed either by graft copolymer or mixture of graft and block copolymers can act as an incorporation site for the hydrophobic drugs. The drug loading content of the graft copolymer micelles tends to be larger when the content of the polypeptide segments in the copolymer increases. The results obtained from the drug-release studies showed that the drug-release rates are dependent on the chemical nature of the graft copolymer, the composition of the graft and block copolymer mixture, and also the pH value of the release media.