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1.
Food Chem ; 336: 127625, 2021 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-32771897

RESUMO

The solubility of carbon dioxide (CO2) in the moisture and protein components of cheese matrices and the influence of changing pH, salt and temperature levels remains unclear. In this study, model casein matrices were prepared, by renneting of micellar casein concentrate (MCC), with modulation of salt and pH levels by adding salt and glucono delta-lactone, respectively, to the MCC solutions prior to renneting. Different moisture-to-protein levels were achieved by freeze-drying, incubation of samples at different relative humidities, or by applying varying pressures during gel manufacture. The CO2 solubility of samples decreased linearly with both increasing temperature and salt-in-moisture content, whereas solubility of CO2 increased with increasing pH. A non-linear relationship was observed between CO2 solubility and the moisture-to-protein ratio of experimental samples. Overall, such knowledge may be applied to improve the quality and consistency of eye-type cheese, and in particular to avoid development of undesirable slits and cracks.


Assuntos
Dióxido de Carbono/química , Caseínas/química , Cloreto de Sódio/química , Água/química , Queijo/análise , Concentração de Íons de Hidrogênio , Pressão Parcial , Solubilidade , Temperatura
2.
Food Chem ; 334: 127526, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32702589

RESUMO

Blueberry anthocyanins are well-known for their diverse biological functions. However, the instability during digestion results in their weak bioavailability. The current study aimed to investigate the alteration in the stability, antioxidant capacity and bioaccessibility of blueberry anthocyanins with the addition of α-casein and ß-casein in a simulated digestion system using pH differential method, HPLC-MS analysis, peroxyl scavenging capacity (PSC) assay, cellular antioxidant activity (CAA) and penetration test. The results showed that both α-casein and ß-casein could increase the stability of blueberry anthocyanins during intestinal digestion and protect their antioxidant capacity. Moreover, the addition of α-casein or ß-casein would enhance the bioaccessibility of blueberry anthocyanins. In conclusion, our study highlights that the interaction between α-casein or ß-casein with blueberry anthocyanins can protect the compounds against influences associated with the simulated digestion.


Assuntos
Antocianinas/química , Antioxidantes/química , Mirtilos Azuis (Planta)/química , Caseínas/química , Antocianinas/metabolismo , Antocianinas/farmacologia , Mirtilos Azuis (Planta)/metabolismo , Caseínas/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Cromatografia Líquida de Alta Pressão , Digestão , Frutas/química , Frutas/metabolismo , Células Hep G2 , Humanos , Concentração de Íons de Hidrogênio , Espectrometria de Massas , Extratos Vegetais/química , Estabilidade Proteica
3.
Food Chem ; 332: 127440, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32652411

RESUMO

Rehydration in an alkaline solution has been shown to improve the rehydration behaviour of milk protein isolate (MPI). In this study, the focus is on citric acid neutralization of MPI powder dissolved in alkaline solution. The results showed that alkalization induced more negative zeta-potential compared to MPI control, reducing it from -22.4 mV to -32.6 mV. Neutralization had a relatively similar zeta-potential value as alkalized sample. Sodium carbonate addition increased pH and caused a consequential reduction of ionic calcium in aqueous phase and, neutralization caused a small increase in ionic calcium. Soluble aggregate of κ-casein protein and whey protein was suggested in alkalization and neutralization process by non-reducing SDS-PAGE. In addition, neutralization kept a stable colloidal particle size for pHs decreased to pH 9,8 and 7; however, alkalization and neutralization created casein aggregates of larger colloidal particle size than primary casein micelle in control MPI.


Assuntos
Cálcio/química , Caseínas/química , Quelantes/química , Animais , Bovinos , Ácido Cítrico/química , Concentração de Íons de Hidrogênio , Micelas , Tamanho da Partícula , Proteínas do Soro do Leite/química
4.
Food Chem ; 332: 127381, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32603917

RESUMO

In this work, three different polyether-modified siloxanes (PMS1, PMS2, and PMS3) were applied to stabilize water-in-oil emulsions, and sodium caseinate (SC) was used to establish water-in-oil-in-water (W/O/W) emulsions. Here, PMS polymers were modified by Isolan GPS and SC by Tween 80. The impact of modifications on the physical stability and controlled release of W/O/W emulsions were investigated. It was found that the storage stability and control release of double emulsions were dependent on the types of PMS used, percent of Isolan GPS, and Tween 80. When PMS1 and PMS2 were combined with low percent of Isolan GPS and Tween 80, the dispersed droplet sizes were reduced, lower percent in the gravitational sedimentation were achieved than using PMS3 emulsions. The controlled releases of Mg2+ from W/O/W emulsions by using PMS3 were slower than using other PMS. PMS3 had a strong influence in controlling the release of Mg2+ from the double emulsions.


Assuntos
Emulsões/química , Siloxanas/química , Caseínas/química , Condutividade Elétrica , Magnésio/metabolismo , Óleos/química , Tamanho da Partícula , Polissorbatos/química , Tensão Superficial , Água/química
5.
Food Chem ; 330: 127324, 2020 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32569938

RESUMO

Enzymes currently used in cheesemaking have various drawbacks, and there is a continual need to find new coagulants. This study describes the extraction and biochemical characterization of two proteases from the red alga Gracilaria edulis. The proteases were extracted with phosphate buffer and partially purified by ammonium sulphate precipitation and dialysis. The enzymes exhibited optimum caseinolytic activity at 60 °C and a pH range of 6-8. They showed a high ratio of milk-clotting over caseinolytic activity, indicating they had an excellent milk-clotting ability. The proteases were confirmed to be serine protease and metalloprotease with molecular weight (MW) of 44 and 108 kDa. They exhibited high hydrolytic activity on κ-caseins, cleaving κ-casein at four main sites, one of which being the same as that of calf rennet, which is the first reported for an algal protease. The findings demonstrated that the proteases could potentially be used as a milk coagulant in cheesemaking.


Assuntos
Caseínas/metabolismo , Gracilaria/enzimologia , Peptídeo Hidrolases/isolamento & purificação , Peptídeo Hidrolases/metabolismo , Alga Marinha/enzimologia , Sulfato de Amônio , Animais , Caseínas/química , Fracionamento Químico , Quimosina/metabolismo , Eletroforese em Gel de Poliacrilamida , Gracilaria/química , Concentração de Íons de Hidrogênio , Hidrólise , Leite/química , Leite/metabolismo , Peso Molecular , Peptídeo Hidrolases/química , Extratos Vegetais/química , Extratos Vegetais/isolamento & purificação , Extratos Vegetais/metabolismo , Alga Marinha/química , Serina Proteases/química , Serina Proteases/isolamento & purificação , Serina Proteases/metabolismo , Espectrometria de Massas em Tandem , Temperatura
6.
Food Chem ; 330: 127245, 2020 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32521399

RESUMO

Dihydromyricetin (DMY) encapsulated zein-caseinate nanoparticles (DZP) were fabricated by antisolvent method. The encapsulation and loading efficiency of DMY in DZP were 90.2% and 22.6% as determined by HPLC. DZP is spherical with particle size and ζ potential of 206.4 nm and -29.6 mV, respectively. Physicochemical characterization showed that DMY existed in amorphous form in DZP and its interaction with proteins was found. The fabrication of DZP significantly improved the stability of DMY. Besides, the diffusion rate of DMY in DZP was faster than its suspensions in both simulated gastric and intestinal fluid. The adhesion of DMY in mice gastrointestinal tract was also improved. Besides DMY itself, its methylated metabolites with further sulfation and glucuronide were identified in rat plasma by UPLC-QTOF-MS. UPLC-QqQ-MS/MS quantitative analysis showed that the oral bioavailability of DMY was 1.95 times enhanced. Besides, the concentration of DMY metabolites in plasma were all increased.


Assuntos
Caseínas/química , Flavonóis/química , Nanopartículas/química , Zeína/química , Animais , Disponibilidade Biológica , Caseínas/metabolismo , Cromatografia Líquida de Alta Pressão , Feminino , Flavonóis/metabolismo , Camundongos , Tamanho da Partícula , Ratos , Espectrometria de Massas em Tandem , Zeína/metabolismo
7.
Food Chem ; 330: 127209, 2020 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32535314

RESUMO

Bovine ß-casein is an amphiphilic protein that exists as a monomer and self-organizes into micelles in aqueous solution. The protein has been used as natural vehicles for bioactives. Trans-resveratrol has received significant attention due to its vast health benefits and conversion to cis-isomer during processing and storage. However, cis-isomer has not yet gained as much attention as that of trans-isomer. In this study, the interaction of ß-casein with trans- and cis-resveratrol was characterized. Trans-resveratrol exhibited a higher affinity for ß-casein than cis-isomer, and ß-casein could bind two isomers simultaneously to form protein-diligand complexes. Both trans- and cis-isomers could be encapsulated into ß-casein micelles with encapsulation efficiencies of ~69% and ~57%, respectively. The ß-casein micelles could delay photo-isomerization of trans-isomer to cis-isomer, while ß-casein-ligand complex showed a better protective effect for both isomers during storage than ß-casein micelles. These results might be useful for the development of protein-based carriers for the polyphenols.


Assuntos
Caseínas/química , Excipientes/química , Resveratrol/química , Animais , Bovinos , Isomerismo , Ligantes , Micelas
8.
Food Chem ; 330: 127218, 2020 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32535315

RESUMO

The objective of this work was to study ß-carotene functionalities (color and antioxidant activity) and practical limitations (aggregate formation, poor solubility and low stability) when included in the aqueous systems containing milk proteins. According to the results, self-association constant of ß-carotene in the presence of casein is 1.7-fold of that calculated for WPI. Casein and WPI were capable of conserving ß-carotene against chemical oxidation up to 15 and 12%, respectively, at 1:5 M ratio of ß-carotene to protein. While, WPI reduced its photodegradation quantum yield from 0.03 to 0.012 compared to 0.017 obtained for casein. A 2.7- and 3.6-fold enhancement in ß-carotene solubility was observed in the presence of 1.5 mg/mL of casein and WPI, respectively. The study of ß-carotene interaction with proteins showed, on the one hand, a negative effect on electron transfer and, on the other hand, improved hydrogen transfer to the radical species in the solution.


Assuntos
Caseínas/química , Proteínas do Soro do Leite/química , beta Caroteno/química , Animais , Emulsões , Oxirredução
9.
J Dairy Sci ; 103(8): 6858-6868, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32534931

RESUMO

Milk that does not coagulate after rennet addition, also called noncoagulating (NC) milk, is unwanted in cheese production due to prolonged processing time. Amounts of whey and casein proteins, genetic variants, as well as posttranslational modifications (PTM) of proteins are all contributing factors in rennet-induced coagulation of milk. In this study, we conducted a wide-ranging investigation of milk proteins in milk samples from 616 Swedish Red dairy cattle using liquid chromatography-high resolution mass spectrometry. Relative concentration of proteins, genetic variants, and PTM were compared between NC milk and coagulating milk. The PTM investigated were phosphorylation of caseins and glycosylation of κ-casein. Several genetic variants and PTM were found, including rare phosphorylation variants of the αS-caseins. Genetic variants were found to effect the expressed amount of different proteins. Further, the effect of protein amounts and PTM on a binary NC milk trait was modeled using a generalized linear model. The model showed that NC milk significantly correlated with higher relative concentrations of α-lactalbumin and ß-casein and lower relative concentrations of ß-lactoglobulin and κ-casein. Regarding PTM of caseins, an effect on NC milk from a lower relative concentration of αS1-casein with 8 phosphate groups were found, even though an effect from total relative concentration of αS1-casein was not found. This study has provided insights into protein variants and PTM important for NC milk to improve this undesirable property.


Assuntos
Proteínas do Leite/metabolismo , Leite/química , Processamento de Proteína Pós-Traducional , Animais , Caseínas/química , Bovinos , Cromatografia Líquida , Quimosina/química , Feminino , Genótipo , Lactalbumina/metabolismo , Lactoglobulinas/metabolismo , Espectrometria de Massas , Fosforilação , Suécia
10.
Artigo em Inglês | MEDLINE | ID: mdl-32361468

RESUMO

The present study aimed to evaluate the effect of the immobilization method of trypsin on biochar on the hydrolysis of casein from different sources, when compared to the process using trypsin in native form, to obtain bioactive peptides. The modification of the surface of biochar with glutaraldehyde was effective, as shown by the results of FTIR assay and the texture profile of the materials. Both activated and functionalized biochar showed high immobilization efficiency (greater than 87%) and high binding capacity (greater than 91 mg/g). During hydrolysis, the biocatalyst obtained by enzyme immobilization on the functionalized biochar presented a higher hydrolysis capacity for the different caseins when compared to the enzyme immobilized by adsorption, with values of 3.05 and 2.73 U/mg for goat casein, 2.36 and 1.85 U/mg for bovine casein, and 2.60 and 2.37 U/mg for buffalo, casein, respectively, with 60 min of reaction. The results of inhibitory activity in this study ranged from 93.5% and 25.5% for trypsin in its free form and immobilized on functionalized activated carbon, respectively, under the same reaction conditions. The immobilization methods were efficient, presenting high immobilization capacity. The proteolytic activity of trypsin immobilized via covalent binding was higher when compared the immobilization by adsorption. Thus, the functionalized biochar has proven to be potential support for enzyme immobilization, and the biocatalyst can be reused for more than 4 cycles. Despite lower ACE inhibition values of hydrolyzed obtained with the immobilized enzymes compared to free enzymes, biocatalysts present advantage due to the possibility of reuse.


Assuntos
Caseínas/química , Carvão Vegetal/química , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Tripsina/química , Tripsina/metabolismo , Adsorção , Animais , Biocatálise , Bovinos , Estabilidade Enzimática , Glutaral/química , Concentração de Íons de Hidrogênio , Hidrólise , Cinética , Ácidos Fosfóricos/química , Proteólise , Propriedades de Superfície , Temperatura
11.
J Dairy Sci ; 103(6): 4975-4990, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32229125

RESUMO

The effect of the addition of caseinomacropeptide (CMP) or desialylated CMP on the heat-induced denaturation and aggregation of whey proteins was investigated in the pH range 3 to 7 after heating at 80°C for 30 min. The rate and temperature of denaturation, the extent of aggregation, and the changes in secondary structure of the whey proteins heated in presence of CMP or desialylated CMP were measured. The sialic acid bound to CMP favored the denaturation and aggregation of whey proteins when the whey proteins were oppositely charged to CMP at pH 4. A transition occurred at pH 6, below which the removal of sialic acid enhanced the stabilizing properties of CMP against the denaturation and aggregation of the whey proteins. At pH >6, the interactions between desialylated CMP and the whey proteins led to more extensive denaturation and aggregation. Sialic acid bound to CMP influenced the denaturation and aggregation behavior of whey proteins in a pH-dependent manner, and this should be considered in future studies on the heat stability of such systems containing CMP.


Assuntos
Caseínas/química , Ácido N-Acetilneuramínico/química , Fragmentos de Peptídeos/química , Proteínas do Soro do Leite/química , Animais , Bovinos , Temperatura Alta , Concentração de Íons de Hidrogênio , Micelas , Desnaturação Proteica
12.
J Dairy Sci ; 103(6): 4907-4918, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32253041

RESUMO

In this study, we investigated the effect of goat milk casein hydrolysates on glucose consumption rate, intracellular glycogen concentration, and mRNA expression of gluconeogenesis-related genes, including phosphoenolpyruvate carboxykinase 1 (PCK1) and glucose-6-phosphatase catalytic subunit (G6PC), in insulin-resistant HepG2 cells. From the obtained hydrolysates, we also purified and characterized novel peptides that ameliorated high-glucose-induced insulin resistance in HepG2 cells. The 3-h hydrolysate caused the highest glucose consumption rate in insulin-resistant HepG2 cells. It also showed positive effects on promoting intracellular glycogenesis and reducing mRNA expression of PCK1 and G6PC. We separated the obtained hydrolysates into 3 fractions (F1, F2, and F3) by gel filtration chromatography; we further purified F1 using reversed-phase HPLC and identified peptides using liquid chromatography-tandem mass spectrometry. The bioactive peptides identified were SDIPNPIGSE (αS1-casein, f195-204), NPWDQVKR (αS2-casein, f123-130), SLSSSEESITH (ß-casein, f30-40), and QEPVLGPVRGPFP (ß-casein, f207-219). Our findings indicated that specific bioactive peptides from goat milk casein hydrolysates ameliorated insulin resistance in HepG2 cells that had been treated with high glucose. This is a first step toward determining whether goat milk casein hydrolysates can be used as food ingredients to ameliorate insulin resistance.


Assuntos
Caseínas/química , Cabras , Resistência à Insulina , Peptídeos/farmacologia , Animais , Caseínas/metabolismo , Caseínas/farmacologia , Cromatografia Líquida de Alta Pressão , Cromatografia Líquida , Gluconeogênese/genética , Glucose/metabolismo , Glicogênio/metabolismo , Cabras/metabolismo , Células Hep G2 , Humanos , Leite/química , Peptídeos/metabolismo
13.
J Dairy Sci ; 103(7): 6003-6014, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32307154

RESUMO

The objective of this study was to use high-pressure-jet (HPJ) processing to produce functional properties in a low-fat (4.5% fat) ice cream mix similar to those seen when emulsifiers are used. Ice cream mix or serum (nonfat portion of the ice cream mix) were subjected to 200 or 400 MPa HPJ processing and compared with a non-HPJ-treated control. A similar non-HPJ-treated formulation but containing polysorbate 80 (0.075% wt/wt) was also used as a control. The mix samples were characterized in terms of their particle size, density, flow properties, stability, crystallization kinetics, and fat-protein interactions. The sample from the mix subjected to 400 MPa HPJ processing (HPJ-M-400) had increased consistency coefficient (5°C; 228 ± 102.7 mPa·s) and particle size (D[4,3]; 16.0 ± 2.5 µm) compared with the non-HPJ-treated control sample, with viscosity and particle size (volume-moment mean diameter, D[4,3]) values of 7.5 ± 0.4 mPa·s and 0.50 ± 0.1 µm, respectively. These differences were attributed to an increase in casein-fat interactions and casein-casein interactions caused by the 400 MPa HPJ treatment, which were observed using confocal scanning laser microscopy and inferred from an increase in protein and fat concentrations in the sediment after ultracentrifugation. Interestingly, the density of HPJ-M-400 was also lower (0.79 ± 0.17 g/mL) than that of the control (1.04 ± 0.00 g/mL) because bubbles were trapped within these complexes. The large casein-fat complexes formed in the HPJ-M-400 sample also appeared to act as steric barriers that slowed ice crystal growth during quiescent freezing. The alterations in physiochemical properties and apparent ice crystal growth induced by the 400 MPa treatment of low-fat ice cream mix have many potential applications, including clean-label confections.


Assuntos
Gorduras/análise , Manipulação de Alimentos/métodos , Sorvetes/análise , Proteínas do Leite/análise , Leite/química , Animais , Caseínas/química , Cristalização , Emulsificantes , Emulsões , Tecnologia de Alimentos , Congelamento , Humanos , Microscopia Confocal , Tamanho da Partícula , Pasteurização , Reologia , Viscosidade
14.
J Dairy Sci ; 103(5): 3980-3993, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32147262

RESUMO

Reduced-fat food products can help to prevent obesity and other diet-related diseases. However, the removal of fat often impairs the sensory and textural properties of foods, leading to low consumer acceptance. In this study, we tested various concentrations of fat replacers (inulin, corn dextrin, polydextrose, and microparticulated whey protein) combined with rennet casein to investigate their effects on the melting behavior, dynamic rheological properties, and hardness of reduced-fat processed cheese. We found that increasing concentrations of inulin and corn dextrin reduced the flowability of cheese in the melting test and can thus be used to inhibit flow during heating. Microparticulated whey protein did not affect flowability but caused an increase in the storage and loss moduli as well as the temperature at gel-sol transition. A similar effect was also shown for rennet casein, whereas inulin and polydextrose had little or no effect on these rheological parameters. Corn dextrin had no effect on the storage and loss moduli, but affected the gel-sol transition temperature. No changes in hardness were detected for any concentration of the fat replacers, but increasing the rennet casein content also increased the hardness of the samples, regardless of the fat replacer used. Our results indicate the different concentrations and combinations of fat replacers and rennet casein that can be included in reduced-fat processed cheese to develop products with specific rheological properties, thus meeting future demand for reduced-fat products with attractive sensory attributes.


Assuntos
Caseínas/química , Queijo , Quimosina/química , Substitutos da Gordura/química , Animais , Queijo/análise , Dureza , Inulina/química , Temperatura , Proteínas do Soro do Leite/química
15.
J Dairy Sci ; 103(5): 3971-3979, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32171507

RESUMO

We investigated the applicability of cryo-electron tomography as a method to quantify changes in the major constituents of casein micelles (i.e., casein proteins, putative colloidal calcium phosphate nanoclusters, and serum-filled voids and channels) in response to their environment. Skim milk diluted 20-fold in milk serum was used for this study. Tomograms were generated for multiple casein micelles at 2 different pH values (6.7 and 6.0) and pixel intensity thresholds were identified for each constituent. The volume of each constituent was determined using these thresholds and expressed as a fraction of micelle volume. At the given dilution, a significant decrease in the volume fractions of casein proteins (∼37%) and putative colloidal calcium phosphate nanoclusters (∼67%) was observed with the reduction of pH from 6.7 to 6.0. Assessment of casein micelle fraction obtained by ultracentrifugation of corresponding skim milk samples produced comparable results. When using such an approach, the imaging conditions, denoising methods, and thresholding approaches used can all affect the precision of the measurements, but the overall trends in constituent volumes are able to be tracked. The primary advantage of using cryo-electron tomography is that analysis can be done at the level of individual micelles, within a 3-dimensional morphological context. This workflow paves the way for high-throughput exploration of milk micelles and how their environment shapes their composition and structure.


Assuntos
Caseínas/química , Bovinos , Tomografia com Microscopia Eletrônica , Micelas , Leite/química , Animais , Fosfatos de Cálcio/química , Concentração de Íons de Hidrogênio , Ultracentrifugação
16.
Food Chem ; 319: 126514, 2020 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-32179369

RESUMO

Caseins and whey proteins are known as 'slow' and 'fast' proteins, respectively, based on their amino acid absorption rate. However, there is limited understanding of the mechanisms controlling their behaviour during gastro-intestinal transit. A protein model system (8% total protein) with varying casein:whey protein ratios (0:100, 20:80, 50:50 and 80:20) were subjected to in vitro gastro-intestinal digestion using a semi-dynamic gastric model, a static intestinal model and an ex vivo absorption model (Ussing chambers). The casein-rich (≥50%) samples showed the formation of solid coagula that were persistent throughout gastric digestion, which caused a delay in nutrient emptying, slower digestion and leucine absorption kinetics. In contrast, whey proteins formed more soluble aggregates during the gastric phase, which led to faster gastric emptying, rapid intestinal hydrolysis, and higher and faster leucine absorption. This work shows the key role of the gastric restructuring for the overall digestive mechanism and kinetics of food, in particular proteins.


Assuntos
Caseínas/química , Lipídeos/química , Proteínas do Soro do Leite/química , Animais , Digestão , Feminino , Esvaziamento Gástrico , Hidrólise , Leucina/química , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Estômago
17.
Artigo em Inglês | MEDLINE | ID: mdl-32172172

RESUMO

Purification of small bioactive peptides from complex biological samples is a difficult task due to the interference of concentrated large biomolecules. In this study, a magnetic immobilized metal affinity chromatography matrix modified by poly (ethylene glycol) methyl ether (IMACM@mPEG) was prepared and applied for the rapid purification of angiotensin I-converting enzyme (ACE) inhibitory peptides from casein hydrolysate. The proposed IMACM@mPEG considerably reduced the non-specific adsorption of large proteins and exhibited improved purification efficiency towards ACE inhibitory peptides. A novel peptide with moderate ACE inhibitory activity (IC50 value of 274 ± 5 µM) was identified as LLYQEPVLGPVR. Lineweaver-Burk plot confirmed the non-competitive inhibition pattern of LLYQEPVLGPVR. The purified peptide was digested after simulated gastrointestinal digestion and produced shorter peptides which contributed to enhanced ACE inhibitory activity. These results indicated that the IMACM@mPEG is an effective method for the prepurification of ACE inhibitory peptide and the purified peptide LLYQEPVLGPVR may have potential as nutraceutical ingredient in functional foods for hypertension treatments.


Assuntos
Inibidores da Enzima Conversora de Angiotensina/isolamento & purificação , Caseínas/química , Cromatografia de Afinidade/métodos , Éteres/química , Peptídeos/isolamento & purificação , Polietilenoglicóis/química , Adsorção , Sequência de Aminoácidos , Inibidores da Enzima Conversora de Angiotensina/análise , Inibidores da Enzima Conversora de Angiotensina/metabolismo , Cobre/química , Óxido Ferroso-Férrico/química , Microesferas , Peptídeos/análise , Peptídeos/metabolismo , Hidrolisados de Proteína , Dióxido de Silício/metabolismo , Propriedades de Superfície
18.
J Agric Food Chem ; 68(9): 2773-2782, 2020 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-32013417

RESUMO

The influence of covalent protein modifications resulting from the Maillard reaction (glycation) of casein and lactose on the noncovalent association behavior of the protein was studied. Nonenzymatic cross-linking with methylglyoxal (MGO) and glutaraldehyde (GTA) as well as enzymatic cross-linking with microbial transglutaminase (mTG) was investigated in comparison. Molar mass, particle size, and conformational characteristics of nonmicellar casein associates as well as the extent of intraparticle protein cross-linking were examined utilizing size-exclusion chromatography (SEC) combined with UV detection and static and dynamic light scattering. Cross-linking resulted in the stabilization of a certain fraction of casein associates, with particle sizes of approximately 30 nm in radius of gyration (Rg), and promoted an incorporation of further casein molecules into those particles, yielding molar masses (Mw) of 1.0-1.2 × 106 g/mol. When caseins were additionally conjugated with lactose during the early Maillard reaction, a further growth of the associates up to approximately 50 nm in Rg with a Mw of 2.1 × 106 g/mol was observed. Furthermore, glycation reactions induced a transition from slightly elongated, random-coil structures toward more anisotropic conformations. Associates consisting of caseins cross-linked with GTA appeared to preserve the original particle conformation.


Assuntos
Caseínas/química , Cromatografia em Gel , Reagentes para Ligações Cruzadas/química , Difusão Dinâmica da Luz , Glutaral/química , Lactose/química , Reação de Maillard , Tamanho da Partícula , Aldeído Pirúvico/química
19.
Food Chem ; 317: 126418, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32087512

RESUMO

The influence of encapsulation with caseins on the stability of cyanidin 3-O-glucoside (C3G) was investigated. The modified casein nanoparticles (MCs) prepared at pH 5.5 after heated at 80 °C for 30 min was applied to encapsulate C3G. The diameter of nanoparticle (MCs-C3G) was 110 ± 0.31 nm and zeta-potential was -8.83 ± 0.52 mV. The molecular weight of α-casein (32 kDa) and ß-casein (25 kDa) increased along with the encapsulation of C3G. The interactions of MCs with C3G were examined at pH 6.3 by fluorescence spectroscopy and IR spectroscopy. MCs encapsulated C3G mainly via the hydrophobic interaction. The secondary structures of caseins were changed along with the combination of C3G, with a decreasing in α-helix, turn random, and coil structure, as well as increased ß-sheet. In addition, the MCs-C3G interaction appeared to have a positive effect on the thermal, oxidation and photo stability of C3G.


Assuntos
Antocianinas/química , Caseínas/química , Glucosídeos/química , Nanopartículas/química , Estabilidade de Medicamentos , Temperatura Alta , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Tamanho da Partícula , Estrutura Secundária de Proteína
20.
Food Chem ; 316: 126199, 2020 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-32036175

RESUMO

The aggregation of a mixed suspension of native and pre-acidified casein micelles was observed using rheology. Pre-acidified micelles were prepared by addition of glucono-delta-lactone, once pH of 6 or 5.5 was reached, the suspension was concentrated and added to untreated skim milk. Gelation was followed by addition of chymosin, for mixes before or after re-equilibration to the original milk pH. When pre-concentrated micelles were acidified, an earlier gelation point was shown, as well as a higher elastic modulus, compared to control suspensions. When skim milk containing pre-acidified micelles was re-equilibrated to the original pH no gelation was observed after addition of chymosin, in spite of very similar levels of diffusible calcium and phosphate concentration to those of the original milk. It was concluded that it may be possible to fine tune the rheological properties of the final chymosin induced gel network, by pretreating only a portion of the casein micelles, and modifying their colloidal calcium phosphate and the ratio of soluble to micellar casein.


Assuntos
Caseínas/química , Quimosina/química , Animais , Cálcio/química , Coloides , Concentração de Íons de Hidrogênio , Leite/química , Fosfatos/química , Suspensões/química
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