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1.
J Photochem Photobiol B ; 202: 111671, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31731076

RESUMO

As a molecular chaperone, ß-casein is difficult to form amyloid fibrils under physiological conditions due to its chaperone activity. Heparan sulfate (HS) has drawn attention of technologists all over the word because of its relation to amyloid deposits in some amyloidosis diseases. For better understanding the relationship between the ß-casein and HS, the multi-spectroscopic studies were employed. The data of thioflavin T (ThT) binding assay, transmission electron microscopy (TEM) and circular dichroism (CD) demonstrated that HS promoted fibril formation by ß-casein in the amount and the growth speed. The results of steady-state UV-vis absorption spectra, fluorescence spectroscopy and fluorescence lifetime revealed that the ß-casein-HS complexes were formed and HS quenched the fluorescence of ß-casein by a static quenching mechanism. On the basis of fluorescence analysis, the value of binding constant was equal to 1.17 × 107 L mol-1 at 338.15 K and there was about one binding site between them. According to thermodynamic parameters obtained, it was deduced that a spontaneous reaction happened, and protein-ligand complex was stabilized by hydrogen bonds and hydrophobic interaction. Furthermore, using fluorescence resonance energy transfer (FRET) assay, the value of binding distance between HS and Trp143 of ß-casein was calculated to be 0.93 nm. Finally, on the basis of synchronous fluorescence experiment, the polarity increasing and hydrophobicity decreasing around Trp143 occurred during the period of fibril formation by ß-casein.


Assuntos
Amiloide/metabolismo , Caseínas/química , Heparitina Sulfato/química , Amiloide/química , Animais , Sítios de Ligação , Caseínas/metabolismo , Bovinos , Dicroísmo Circular , Transferência Ressonante de Energia de Fluorescência , Heparitina Sulfato/metabolismo , Interações Hidrofóbicas e Hidrofílicas , Microscopia Eletrônica de Transmissão , Ligação Proteica , Termodinâmica
2.
J Agric Food Chem ; 68(2): 652-659, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31869222

RESUMO

Casein phosphopeptides are known to enhance zinc absorption, but the underlying mechanism remains unclear. Here, a gastrointestinal casein hydrolysate (CH) was found to keep zinc in solution despite heavy precipitation of calcium and phosphate, the omnipresent mineral nutrients that could co-precipitate zinc out of solution instantly and almost completely under physiologically relevant conditions. Dynamic light scattering, transmission electron microscopy, and energy-dispersive X-ray analysis displayed the CH-mediated formation of zinc/calcium phosphate (Zn/CaP) nanocomplexes aggregated from rather small nanoclusters. The ex vivo mouse ileal loop experiments revealed enhanced intestinal zinc absorption by CH's prevention of zinc co-precipitation with CaP, and the treatments with specific inhibitors unveiled the involvement of macropinocytic internalization, lysosomal degradation, and transcytosis in the intestinal uptake of zinc from Zn/CaP nanocomplexes. A low calcium-to-phosphorus ratio adversely affected CH's efficiency to enhance zinc solubility and absorption. Overall, our study provides a new paradigm for casein phosphopeptides to improve zinc bioavailability.


Assuntos
Fosfatos de Cálcio/química , Caseínas/química , Intestino Delgado/metabolismo , Zinco/química , Zinco/metabolismo , Animais , Disponibilidade Biológica , Fosfatos de Cálcio/metabolismo , Caseínas/metabolismo , Absorção Intestinal , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Nanopartículas/química , Nanopartículas/metabolismo
3.
Food Chem ; 309: 125764, 2020 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-31771916

RESUMO

Coating fruits surface with biodegradable films obtained from starch is an alternative to delay the fruit ripening process. This study aimed to develop a biodegradable film from a polymer blend consisting of natural cassava starch, casein, and gelatin, and using sorbitol as the plasticizer. Among all the prepared biodegradable films (BFs), the one with desirable results in thickness, opacity, solubility, and water vapor transmission rate (WVTR) analyzes was based on a high concentration of starch, and casein, and low concentration of gelatin. Also, this film had the lowest solubility among all of them. Guava fruit coated with this film showed a two-day increase in shelf-life when compared to non-coated guavas. The increase in shelf-life was due to the extremely low water vapor transmission rate of the films, decreasing the fruits' mass loss, and, consequently, retarding their senescence. These results indicate that the biodegradable film is a promising material for fruit coating.


Assuntos
Caseínas/química , Gelatina/química , Amido/química , Frutas/química , Permeabilidade , Psidium/química , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Água/química
4.
Food Chem ; 309: 125758, 2020 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-31699551

RESUMO

Emulsions were designed under low frequency ultrasound (20 kHz) at energy densities of 11.7-117.0 J/mL using grape seed oil and milk protein solutions containing different casein to whey protein ratios of 80:20, 60:40, 50:50 and 40:60. An increase in energy densities produced emulsions with a smaller droplet size and narrow size distribution at all milk protein ratios. However, the minimum sono-energy density required to produce stable emulsions varied depending on the ratio of caseins (CN) and whey proteins (WP) in the continuous phase. In addition, the composition of the interfacial layer was dependent on the composition of the milk proteins in the continuous phase. The interfacial layer was predominantly covered by the CN and CN-WP aggregates in the presence of equal or greater amounts of caseins than whey proteins (80:20, 60:40 and 50:50), while WP aggregates and CN-WP aggregates were the primary constituents of whey protein-rich emulsions (40:60).


Assuntos
Emulsões/química , Proteínas do Leite/química , Óleos Vegetais/química , Vitis/metabolismo , Caseínas/química , Tamanho da Partícula , Sementes/metabolismo , Sonicação , Proteínas do Soro do Leite/química
5.
J Agric Food Chem ; 67(49): 13684-13693, 2019 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-31742396

RESUMO

A novel BL312 milk-clotting enzyme (MCE) exhibited high-level expression and remarkable milk-clotting activity (MCA) (865 ± 20 SU/mL) that was 3.3-fold higher than the control by optimizing induction conditions in recombinant Escherichia. coli harboring pET24a-proMCE. Through substrate-binding region analyses and modification, MCE-G165A was identified from nine mutants and showed a proteolytic activity of 49.4 ± 2.4 U/mL and an MCA/PA ratio of 18.2, which were respectively 1.9-fold lower and 2.0-fold higher than those of the control. The purified MCE-G165A (28 kDa) exhibited weak αs-casein, ß-casein, and strong κ-casein (κ-CN) hydrolysis levels as assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and reversed-phase high-performance liquid chromatography. The milk-clotting mechanism for MCE-G165A was the primary hydrolysis of Met106-Ala107 and Asn123-Thr124 bonds in κ-CN, as determined by mass spectrometry. MCE-G165A showed different hydrolysis sites in casein, leading to various functional peptides. Feasible methods for obtaining MCEs suitable as calf rennet substitutes are presented.


Assuntos
Bacillus licheniformis/enzimologia , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Caseínas/química , Quimosina/química , Quimosina/genética , Leite/química , Sequência de Aminoácidos , Animais , Proteínas de Bactérias/metabolismo , Caseínas/metabolismo , Bovinos , Queijo/análise , Queijo/microbiologia , Quimosina/metabolismo , Hidrólise , Engenharia de Proteínas , Proteólise , Alinhamento de Sequência
6.
J Agric Food Chem ; 67(48): 13228-13236, 2019 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-31610115

RESUMO

In this study, a novel plant-protein-based nanoparticle delivery system was developed to encapsulate and stabilize curcumin and epigallocatechin gallate (EGCG) with different polarities. The strongly hydrophobic curcumin was embedded within the hydrophobic cores of zein nanoparticles using an antisolvent method, while the weakly hydrophobic EGCG was adsorbed to the region between the zein core and caseinate shell. The physicochemical properties, structure, and stability of the core-shell particles were characterized using dynamic light scattering, particle electrophoresis, fluorescence spectroscopy, and Fourier transform infrared spectroscopy. The bioaccessibility of curcumin in the core-shell nanoparticles was determined using a simulated gastrointestinal tract. Mean particle diameters around 100-200 nm could be produced by modulating the mass ratio of curcumin to zein. The encapsulation efficiency of curcumin in the core-shell nanoparticles was higher (96.2%) in the presence of EGCG than in its absence (77.9%). Moreover, the water dispersibility and 1,1-diphenyl-2-picrylhydrazyl radical scavenging capacity of the nanoparticles were significantly improved in the presence of EGCG. The simulated gastrointestinal tract experiments indicated that curcumin had a high bioaccessibility in the optimized core-shell nanoparticles. Overall, our findings suggest that EGCG can be used to improve the functional properties of curcumin-loaded zein-caseinate nanoparticles, which may increase their use in food, cosmetics, and pharmaceutical applications.


Assuntos
Caseínas/química , Catequina/análogos & derivados , Curcumina/química , Zeína/química , Disponibilidade Biológica , Catequina/química , Curcumina/metabolismo , Composição de Medicamentos , Trato Gastrointestinal/metabolismo , Humanos , Interações Hidrofóbicas e Hidrofílicas , Modelos Biológicos , Nanopartículas/química , Nanopartículas/metabolismo , Tamanho da Partícula
7.
J Agric Food Chem ; 67(43): 12094-12104, 2019 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-31566978

RESUMO

A large portion of Maillard reaction products (MRPs) cannot be absorbed in the upper gut and therefore may be further decomposed and utilized by colonic microbiota (CM). This work reported the stability of UV-absorbent MRPs, fluorescent MRPs and peptide-bound N(ε)-(carboxymethyl)-lysine (CML) in high molecular weight (HMW, >10 kDa), medium molecular weight (MMW, 1-10 kDa), and low molecular weight (LMW, <1 kDa) gastrointestinal digests of glyoxal-glycated casein in the presence of CM. Fluorescent MRPs showed high stability, whereas UV-absorbent MRPs may be partially decomposed. A higher depletion rate of CML was found in the LMW fraction (38.7%) than in the MMW (21.7%) and HMW (9.6%) fractions. The 16S rRNA sequencing results revealed both beneficial and detrimental changes in CM composition induced by the glycated fractions. Generation of short-chain and branched-chain fatty acids in fermentation solutions with glycated fractions was significantly suppressed compared with that in fermentation solution with unglycated digests. This work revealed the possible interplay between peptide-bound MRPs and CM.


Assuntos
Caseínas/metabolismo , Colo/microbiologia , Microbioma Gastrointestinal , Produtos Finais de Glicação Avançada/metabolismo , Glioxal/metabolismo , Peptídeos/metabolismo , Adulto , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Bactérias/metabolismo , Caseínas/química , Colo/metabolismo , Ácidos Graxos Voláteis/metabolismo , Feminino , Produtos Finais de Glicação Avançada/química , Glioxal/química , Humanos , Reação de Maillard , Masculino , Peptídeos/química , Adulto Jovem
8.
Ultrason Sonochem ; 58: 104525, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31554147

RESUMO

Low-frequency sonication (20 kHz) was applied to sodium caseinate suspensions (4%, 7% and 10% protein concentrations) at pH 4.0, 4.6, 6.7 and 9.0. Particle size, zeta potential and solubility analysis were used to evaluate the physical changes of the sodium caseinate suspensions before and after the application of ultrasound. At pH 6.7 the particle size remained between 5 and 7 µm for all concentrations before and after sonication (15-400 J/mL), resulting in no significant change (p > 0.05). Similarly, sonication did not significantly (p > 0.05) affect the solubility at pH 6.7. At this pH, the initial solubility was high at 94-98% (w/w) before sonication. At pH 9.0 for 4% and 7% concentrations, suspensions became more negatively charged and the initial particle size increased to 78-82 µm. In the presence of larger suspensions, the application of ≥15 J/mL reduced the particle size to less than 2 µm. By contrast to pH 6.7, the solubility at pH 9.0 for 4% and 7% protein suspensions reached 99% before and after sonication. Viscosity was the highest (80 mPa.s at 15 sec-1) for a 10% protein concentration at pH 9.0. As the protein concentration of the sodium caseinate suspensions decreased from 10% to 4% at pH 9.0, the viscosity of the suspensions also decreased. However, application of low-frequency ultrasound had no effect on the viscosity of the sodium caseinate suspensions. Due to the absence of large insoluble aggregates in reconstituted sodium caseinate suspensions, the overall effect of low-frequency sonication were largely insignificant at native pH and only became evident at outlier pH values when the casein proteins associate.


Assuntos
Caseínas/química , Tamanho da Partícula , Sonicação , Solubilidade , Propriedades de Superfície , Viscosidade
9.
J Agric Food Chem ; 67(42): 11778-11787, 2019 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-31554398

RESUMO

Casein is a rich source of bioactive peptides with complete amino acid composition. In this study, the casein peptides identified in our previous study with different hydrophobicities and charge properties were employed to investigate the transport efficiency via the transcytosis pathway across Caco-2 cell monolayers. Results revealed that the apparent permeability coefficient (Papp) values of transcytosis exhibited a linear correlation with a pI of positively charged peptides during bidirectional transport. A similar law was found as for the peptides with different hydrophobicities. The transcytosis route of Pep-II to Pep-VII appears to be the clathrin- and caveolin-independent transcytosis pathway as well as caveolae-mediated transcytosis pathway, showing a linear correlation with Papp values, respectively. Additionally, no direct correlation was shown between the hydrophobicity of peptides and clathrin-mediated transcytosis. Our results help to increase the bioaccessibility of peptide drugs across intestinal mucosa by developing strategies to alter the physicochemical properties without changing bioactivity.


Assuntos
Caseínas/química , Peptídeos/metabolismo , Células CACO-2 , Caseínas/metabolismo , Humanos , Interações Hidrofóbicas e Hidrofílicas , Cinética , Peptídeos/química , Permeabilidade , Transcitose
10.
Molecules ; 24(16)2019 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-31398828

RESUMO

One of the conventional ways to produce lactose-hydrolyzed (LH) milk is via the addition of commercial lactases into heat-treated milk in which lactose is hydrolyzed throughout storage. This post-hydrolysis method can induce proteolysis in milk proteins due to protease impurities remaining in commercial lactase preparations. In this work, the interplay between lactose hydrolysis, proteolysis, and glycation was studied in a model system of purified ß-casein (ß-CN), lactose, and lactases using peptidomic methods. With a lactase presence, the proteolysis of ß-CN was found to be increased during storage. The protease side-activities mainly acted on the hydrophobic C-terminus of ß-CN at Ala, Pro, Ile, Phe, Leu, Lys, Gln, and Tyr positions, resulting in the formation of peptides, some of which were N-terminal glycated or potentially bitter. The proteolysis in ß-CN incubated with a lactase was shown to act as a kind of "pre-digestion", thus increasing the subsequent in vitro digestibility of ß-CN and drastically changing the peptide profiles of the in vitro digests. This model study provides a better understanding of how the residual proteases in commercial lactase preparations affect the quality and nutritional aspects of ß-CN itself and could be related to its behavior in LH milk.


Assuntos
Caseínas/química , Lactase/química , Sequência de Aminoácidos , Animais , Cromatografia Líquida , Digestão , Hidrólise , Leite/química , Proteínas do Leite/química , Peptídeos/química , Proteólise , Espectrometria de Massas em Tandem
11.
Int J Mol Sci ; 20(16)2019 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-31398861

RESUMO

The work presents the kinetic and isotherm studies of silver binding on casein, which was carried out using batch sorption technique. Moreover, the influence of light irradiation on the process was shown. In order to investigate the mechanism of metal ions sorption by casein the zero, pseudo-first order kinetics and Weber-Morris intra-particle diffusion as well as Langmuir and Freundlich isotherm models were used. Furthermore, to specify more precisely, the possible binding mechanism, the spectroscopic (FT-IR-Fourier Transform Infrared Spectroscopy, Raman), spectrometric (MALDI-TOF MS-Matrix-Assisted Laser Desorption/Ionization Time Of Flight Mass Spectrometry), microscopic (SEM-Scanning Electron Microscope, TEM/EDX-Transmission Electron Microscopy/Energy Dispersive X-ray detector) and thermal (TGA-Thermogravimetric Analysis, DTG-Derivative Thermogravimetry) analysis were performed. Kinetic study indicates that silver binding onto casein is a heterogeneous process with two main stages: initial rapid stage related to surface adsorption onto casein with immediate creation of silver nanoparticles and slower second stage of intraglobular diffusion with silver binding in chelated form (metalloproteins) or ion-exchange form. Spectroscopic techniques confirmed the binding process and MALDI-TOF MS analysis show the dominant contribution of the α-casein in the process. Moreover, the treatment of silver-casein complex by artificial physiological fluids was performed.


Assuntos
Caseínas/química , Íons/química , Prata/química , Concentração de Íons de Hidrogênio , Cinética , Nanopartículas Metálicas/química , Nanopartículas Metálicas/ultraestrutura , Metaloproteínas/química , Modelos Teóricos , Ligação Proteica , Análise Espectral , Termodinâmica , Termogravimetria
12.
Molecules ; 24(16)2019 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-31408975

RESUMO

Intrinsically disordered proteins play a central role in dynamic regulatory and assembly processes in the cell. Recently, a human κ-casein proteolytic fragment called lactaptin (8.6 kDa) was found to induce apoptosis of human breast adenocarcinoma MCF-7 and MDA-MB-231 cells with no cytotoxic activity toward normal cells. Earlier, we had designed some recombinant analogs of lactaptin and compared their biological activity. Among these analogs, RL2 has the highest antitumor activity, but the amino acid residues and secondary structures that are responsible for RL2's activity remain unclear. To elucidate the structure-activity relations of RL2, we studied the structural and aggregation features of this fairly large intrinsically disordered fragment of human milk κ-casein by a combination of physicochemical methods: NMR, paramagnetic relaxation enhancement (PRE), Electron Paramagnetic Resonance (EPR), circular dichroism, dynamic light scattering, atomic force microscopy, and a cytotoxic activity assay. It was found that in solution, RL2 exists as stand-alone monomeric particles and large aggregates. Whereas the disulfide-bonded homodimer turned out to be more prone to assembly into large aggregates, the monomer predominantly forms single particles. NMR relaxation analysis of spin-labeled RL2 showed that the RL2 N-terminal region, which is essential not only for multimerization of the peptide but also for its proapoptotic action on cancer cells, is more ordered than its C-terminal counterpart and contains a site with a propensity for α-helical secondary structure.


Assuntos
Antineoplásicos/química , Caseínas/química , Peptídeos Penetradores de Células/química , Proteínas Intrinsicamente Desordenadas/química , Sequência de Aminoácidos , Antineoplásicos/metabolismo , Antineoplásicos/farmacologia , Caseínas/biossíntese , Caseínas/genética , Caseínas/farmacologia , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Peptídeos Penetradores de Células/biossíntese , Peptídeos Penetradores de Células/genética , Peptídeos Penetradores de Células/farmacologia , Clonagem Molecular , Escherichia coli/genética , Escherichia coli/metabolismo , Expressão Gênica , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Humanos , Proteínas Intrinsicamente Desordenadas/biossíntese , Proteínas Intrinsicamente Desordenadas/genética , Proteínas Intrinsicamente Desordenadas/farmacologia , Células MCF-7 , Agregados Proteicos/genética , Multimerização Proteica , Estrutura Secundária de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Proteínas Recombinantes/farmacologia , Relação Estrutura-Atividade
13.
J Agric Food Chem ; 67(38): 10604-10613, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31466448

RESUMO

The aim of this study was to investigate the dipeptidyl peptidase-IV (DPP-IV) inhibition and metabolic stability of a casein-derived peptide Val-Pro-Tyr-Pro-Gln (VPYPQ) and its fragments as well as their release from casein following hydrolysis. Results showed that VPYPQ was the most potent DPP-IV inhibitory peptide among them with an IC50 value of 41.45 µM. This might be due to its two internal Pro residues at positions 2 and 4. Moreover, VPYPQ was resistant to hydrolysis by gastrointestinal enzymes and was relatively more stable to hydrolysis by DPP-IV and peptidases in plasma compared with its fragments. Additionally, oral administration of VPYPQ at a dose of 90 µmol/kg body weight could reduce the postprandial blood glucose levels in mice. More importantly, VPYPQ could be released efficiently from casein following hydrolysis by a combination of papain and in vitro digestion, reaching up to 3211.15 µg/g. Therefore, VPYPQ was a promising casein-derived DPP-IV inhibitor.


Assuntos
Caseínas/química , Preparações de Ação Retardada/química , Inibidores da Dipeptidil Peptidase IV/química , Peptídeos/química , Animais , Biocatálise , Glicemia/metabolismo , Preparações de Ação Retardada/administração & dosagem , Diabetes Mellitus/tratamento farmacológico , Diabetes Mellitus/metabolismo , Dipeptidil Peptidase 4/química , Dipeptidil Peptidase 4/metabolismo , Inibidores da Dipeptidil Peptidase IV/administração & dosagem , Teste de Tolerância a Glucose , Humanos , Hidrólise , Camundongos , Peptídeo Hidrolases/química , Peptídeo Hidrolases/metabolismo , Peptídeos/administração & dosagem , Ratos , Ratos Sprague-Dawley
14.
J Food Sci ; 84(9): 2584-2591, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31436860

RESUMO

The potential of heterogeneous systems like oil-in-water (O/W) nanoemulsions is exploited as an oral delivery system for curcumin, a natural lipophilic compound with numerous health benefits. Two types of O/W nanoemulsions, one stabilized by sodium caseinate (Cas-O/W), a surface-active and emulsifying protein, and the other stabilized by a blend of caseinate and Tween 20 (Mix-O/W), were loaded with the bioactive compound and tested through a simulated gastrointestinal digestion process to evaluate their effects on delivering of curcumin. It was first demonstrated that the amount of curcumin solubilized through Mix-O/W nanoemulsion was higher than that in Cas-O/W nanoemulsion. Cas-O/W nanoemulsions, indeed, at their best, solubilized about 55 µg/mL of curcumin while Mix-O/W nanoemulsions reached a curcumin concentration around 180 µg/mL. Furthermore, for both the systems an increase of curcumin loading capacity was recorded with the rise of incubation temperature. Finally, after the in vitro simulated digestion process, the potential curcumin bioavailability was evaluated and the data suggested that Mix-O/W nanoemulsions provided more than twice the amount of curcumin compared to Cas-O/W nanoemulsions. On balance, the outcomes of this investigation demonstrated that the mixed emulsifier system offered a higher amount of lipophilic compound with a low fat intake compared to nanoemulsions stabilized by sodium caseinate. PRACTICAL APPLICATION: The outcomes of this study allow the recognition of the protein/surfactant-stabilized nanoemulsions as a suitable solution to deliver curcumin. The nanoemulsions proposed here provide a high intake of curcumin, a lipophilic compound, with low fat content. The use of such delivery systems helps to overcome limits in oral bioavailability related with the scarce solubility of some compounds in food preparations and beverages.


Assuntos
Caseínas/química , Curcumina , Emulsões/química , Nanopartículas/química , Tensoativos/química , Disponibilidade Biológica , Curcumina/química , Curcumina/farmacocinética , Digestão/fisiologia , Modelos Biológicos , Polissorbatos/química
15.
J Food Sci ; 84(9): 2421-2431, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31404478

RESUMO

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.


Assuntos
Luteína/química , Resveratrol/química , Caseínas/química , Dextranos/química , Composição de Medicamentos , Estabilidade de Medicamentos , Emulsões/química , Temperatura Ambiente
16.
J Dairy Res ; 86(3): 374-376, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31439054

RESUMO

In this Research Communication we present a study of the effect of Ca-binding salts on the recovery of milk fat globule membrane (MFGM) from buttermilk. Sodium phosphate buffer was used for the purpose of MFGM recovery from buttermilk for the first time and we showed that 0.1 M buffer at pH 7.2 was the most effective for the recovery of MFGM. The fact of high efficacy of sodium phosphate buffer in recovery of MFGM from buttermilk allowed us to suggest that MFGM in buttermilk is present in association with casein through Ca- bridges formed between phospholipids of MFGM and phosphate groups of casein, primarily with k-casein as the peripheral protein of casein micelles.


Assuntos
Leitelho/análise , Cálcio/química , Glicolipídeos/isolamento & purificação , Glicoproteínas/isolamento & purificação , Fosfatos , Animais , Tampões (Química) , Caseínas/química , Suplementos Nutricionais/análise , Manipulação de Alimentos/métodos , Fosfatos/química , Fosfolipídeos/química
17.
Anal Chim Acta ; 1079: 111-119, 2019 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-31387701

RESUMO

Developing an effective strategy for endogenous phosphopeptides enrichment and separation is necessary in phosphopeptidomics analysis due to the serious inference caused by chaotic biological environment. In this work, a size-exclusive magnetic binary metal mesoporous nanocomposites were synthesized to capture phosphorylated peptides for mass spectrometry analysis. The novel Fe3O4@TiO2-ZrO2@mSiO2 nanocomposites possessed the merits of ordered mesoporous channels, superparamagnetism and the integration of dual affinity of Zr-O and Ti-O. Compared with single-metal centered nanocomposites (Fe3O4@TiO2@mSiO2 and Fe3O4@ZrO2@mSiO2), Fe3O4@TiO2-ZrO2@mSiO2 showing much enhanced enrichment performance towards mono- and multi-phospho-peptides with better sensitivity. With all the advances, the Fe3O4@TiO2-ZrO2@mSiO2 was also successfully applied to capture endogenous phosphorylated peptides from human saliva. And consequently, a total of 30 phosphopeptides containing 2 multi- and 28 mono-phosphopeptides were identified efficiently. These results show that the novel materials have the great potential in peptidome analysis.


Assuntos
Nanopartículas de Magnetita/química , Nanocompostos/química , Fosfopeptídeos/análise , Saliva/química , Dióxido de Silício/química , Animais , Caseínas/química , Bovinos , Humanos , Proteômica/métodos , Soroalbumina Bovina/química , Titânio/química , Zircônio/química
18.
J Dairy Sci ; 102(10): 8696-8703, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31351722

RESUMO

Caseinomacropeptide (CMP) is an important polypeptide found in cheese whey that has various biological activities and functional properties. Because sialylations play an important role in the functional properties of CMP, the aim of the present work was to characterize CMP isoform heterogeneity in a commercial glycosylated CMP (gCMP) isolate using liquid chromatography- and gel-based proteomics before and after desialidation. Using 2-dimensional gel electrophoresis (2-DGE), we observed a shift in isoelectric point (pI) after enzymatic desialidation, indicating that sialylated gCMP were located at pI 3.0 to 3.1, but desialylated gCMP had repositioned to pI 3.7 to 3.9. We used liquid chromatography/mass spectroscopy (LC-ESI/MS) for further analysis of the glycan chains of gCMP. In total, we identified 19 CMP isoforms, of which 13 were glycosylated and 6 were nonglycosylated. We also detected 3 genetic variants (A, B, and E), with up to 3 glycosylations attached per gCMP. Further, we identified up to 4 isomers, reflecting different sites of glycosylation in the peptide backbone of these isoforms. The dominating gCMP isoform of genetic variant E appeared to contain 4 N-acetyl-neuraminic acid (NeuAc) residues, whereas the dominating gCMP isoforms of variants A and B appeared to contain 2 NeuAc. The identification revealed conversions of isoforms containing different combinations of genetic variants and degrees of glycosylation, sialylation, and phosphorylation to various desialylated counter-isoforms. The content of sialylated gCMP relative to the total CMP content was 37% (wt/wt), which decreased to 1.5% after sialidase treatment, indicating 96% effectivity of the desialidation. This approach can be valuable for future functionality studies specifically addressing the importance of NeuAc.


Assuntos
Caseínas/química , Fragmentos de Peptídeos/química , Animais , Bovinos , Queijo , Cromatografia Líquida , Glicosilação , Ácido N-Acetilneuramínico , Ácidos Neuramínicos/análise , Isoformas de Proteínas/análise , Proteômica
19.
J Dairy Sci ; 102(9): 7863-7873, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31326163

RESUMO

The effect of the contents of casein (CN) and whey protein fractions on curd yield (CY) and composition was estimated using 964 individual milk samples. Contents of αS1-CN, αS2-CN, ß-CN, γ-CN, glycosylated κ-CN (Gκ-CN), unglycosylated κ-CN, ß-LG, and α-LA of individual milk samples were measured using reversed-phase HPLC. Curd yield and curd composition were measured by model micro-cheese curd making using 25 mL of milk. Dry matter CY (DMCY) was positively associated with all casein fractions but especially with αS1-CN and ß-CN. Curd moisture decreased at increasing ß-CN content and increased at increasing γ-CN and Gκ-CN content. Due to their associations with moisture, Gκ-CN and ß-CN were the fractions with the greatest effect on raw CY, which decreased by 0.66% per 1-standard deviation (SD) increase in the content of ß-CN and increased by 0.62% per 1-SD increase in the content of Gκ-CN. The effects due to variation in percentages of the casein fractions in total casein were less marked than those exerted by contents. A 1-SD increase in ß-CN percentage in casein (+3.8% in casein) exerted a slightly negative effect on DMCY (ß = -0.05%). Conversely, increasing amounts of αS1-CN percentage were associated with a small increase in DMCY. Hence, results suggest that, at constant casein and whey protein contents in milk, the DMCY depends to a limited extent on the variation in the αS1-CN:ß-CN ratio. κ-Casein percentage did not affect DMCY, indicating that the positive relationship detected between the content of κ-CN and DMCY can be attributed to the increase in total casein resulting from the increased amount of κ-CN and not to variation in κ-CN relative content. However, milk with increased Gκ-CN percentage in κ-CN also shows increased raw CY and produces curds with increased moisture content. Curd yield increased at increasing content and relative proportion of ß-LG in whey protein, but this is attributable to an improved capacity of the curd to retain water. Results obtained in this study support the hypothesis that, besides variation in total casein and whey protein contents, variation in protein composition might affect the cheese-making ability of milk, but this requires further studies.


Assuntos
Caseínas/química , Queijo/análise , Leite/química , Proteínas do Soro do Leite/química , Animais , Glicosilação , Lactoglobulinas/metabolismo , Água/análise
20.
J Dairy Sci ; 102(9): 7747-7759, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31326173

RESUMO

We determined seasonal variations in the composition and characteristics of bovine milk, as well as heat-induced changes in the physicochemical properties of the milk, in a typical seasonal-calving New Zealand herd over 2 full milking seasons. Fat, protein, and lactose contents varied consistently during the year in patterns similar to those of the lactation cycle. Seasonality also had significant effects on milk calcium, ionic calcium, fat globule size, buffering capacity, and ethanol stability, but not on casein micelle size. The ratio of casein to total protein did not vary significantly over the season, but late-season milk had the highest content of glycosylated κ-casein (G-κ-CN) and the lowest content of α-lactalbumin in both years. We observed significant between-year effects on protein, total calcium, ionic calcium, pH, and casein:total protein ratio, which might have resulted from different somatic cell counts in the 2 years. Compared with heating at 90°C for 6 min, UHT treatment (140°C for 5 s) induced greater dissociation of κ-casein, a similar extent of whey protein denaturation, a lower extent of whey protein-casein micelle association, and a larger increase in casein micelle size. Indeed, UHT treatment might have triggered significant dissociation of G-κ-CN, resulting in aggregation among the casein micelles and increased apparent mean casein micelle diameter. Seasonality had significant effects on the partitioning of G-κ-CN between the micelle and the serum phase, the extent of whey protein-casein micelle association under both heating conditions, and the casein micelle size of the UHT milk.


Assuntos
Bovinos , Temperatura Alta , Proteínas do Leite/química , Leite/química , Estações do Ano , Proteínas do Soro do Leite/química , Criação de Animais Domésticos , Animais , Caseínas/química , Feminino , Micelas
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