Presence Of Casein Research Articles

Effects of composition and relative humidity on the functional and storage properties of spray dried model milk emulsions

This study investigates the effect of relative humidity (RH) and milk composition on the changes in solubility, lactose crystallinity and protein structural form on a commercial infant formula, by identifying the interactions between water, lactose and protein at different storage conditions. Two spray dried model milk emulsions were studied for comparison, by storing these powders under varying relative humidity (RH) levels between 11 and 94% at room temperature. The properties of powders were evaluated from the degree of insolubility, the rate of browning, and the extent of protein denaturation. The model samples were found to be more stable than the commercial powder, even at high relative humidity (>50% RH). The difference was attributed to the presence of casein, which did not denature to the same extent as whey protein. The results also suggested that minerals present in the commercial powder could be responsible in enhancing protein denaturation, thus accelerating the rate of browning and decreasing solubility.

Role of Fungal Enzymes in the Biochemistry of Egyptian Ras Cheese during Ripening Period

Six fungal genera including thirteen species isolated from Ras cheese samples were tested for assimilation of lactose, skim and fat milk hydrolysis. All fungal strains gave negative results in lactose assimilation except A. nidulans which produced acid without gas after 24 hr and produced a soluble red pigment after 10 days of incubation. All tested fungal strains showed positive results for protein hydrolysis on modified Czapek agar (MCA) medium by skim milk addition. The presence of casein in the cultural medium caused a strong growth comparing with the growth on control. Changing of growth resulting from milk casein addition was in the highest values in the cultures of Rhizopus stolonifer, A. flavus and A. niger being 87.81, 58.32 and 41.58 mm, respectively and the lowest values were A. nidulans and Geotrichum candidum being 7.09 and 13.71 mm. All strains gave positive results for lipolysis except Aspergillus nidulans on plates containing modified Czapek agar (MCA) medium by milk fat addition. The fungal growth diameter was varied from 9.17 to 30.67 mm in the case of A. niger and A. alliaceus, respectively. The presence of milk fat in the cultural medium caused a changing of growth in the case of A. glaucus; A. alliaceus and A. flavus being 28.11, 27.42 and 25.19 mm, respectively and A. niger, Rhizopus stolonifer and A. flavipes achieved lowest values being 5.62, 10.80 and 11.82 mm, respectively. Moisture percentage was gradually decreased during storage period (3 months at 15.5°C) from 31.29% in the first month to 30.25% in the third month. Fat percentage was 24.05% in fresh Ras cheese wheels, which increased to 25.89% after salting period (45 day). During ripening period the values of fat in Ras cheese wheels were 30.53%, 35.98% and 32.38% after the 1st, 2nd and 3rd month, respectively. The highest values of total nitrogen, soluble nitrogen and non-protein nitrogen percentages of Ras cheese wheels were 4.18%, 43.97% and 18.98%, respectively. These values tended to increase with advanced storage.

Methods for determining keratinolytic activity of saprophytic fungi

In order to evaluate tbe keratinolytic activity of saprophytic microfungi the following values were determined, the percentage keratin substrate decomposition (native feathers). the changes of pH of medium the liberation of peptidic substances in this process, as well as the liberation of amine nitrogen and cystein. The presence of keratinase was examined in culture filtrates and the proteolytic activity in the presence of casein. It was noted that among the above mentioned indices the percentage decrease of substrate mass was the most useful criterion of keratinolytic activity evaluation.

Comparative secretome analysis of Streptomyces scabiei during growth in the presence or absence of potato suberin.

BackgroundSuberin is a recalcitrant plant biopolymer composed of a polyphenolic and a polyaliphatic domain. Although suberin contributes to a significant portion of soil organic matter, the biological process of suberin degradation is poorly characterized. It has been suggested that Streptomyces scabiei, a plant pathogenic bacterium, can produce suberin-degrading enzymes. In this study, a comparative analysis of the S. scabiei secretome from culture media supplemented or not with potato suberin was carried out to identify enzymes that could be involved in suberin degradation.MethodsS. scabiei was grown in the presence of casein only or in the presence of both casein and suberin. Extracellular proteins from 1-, 3- and 5-day-old supernatants were analyzed by LC-MS/MS to determine their putative functions. Real-time RT-PCR was performed to monitor the expression level of genes encoding several proteins potentially involved in suberin degradation.ResultsThe effect of suberin on the extracellular protein profile of S. scabiei strain has been analyzed. A total of 246 proteins were found to be common in the data sets from both casein medium (CM) and casein-suberin medium (CSM), whereas 124 and 139 proteins were detected only in CM or CSM, respectively. The identified proteins could be divided into 19 functional groups. Two functional groups of proteins (degradation of aromatic compounds and secondary metabolism) were only associated with the CSM. A high proportion of the proteins found to be either exclusively produced, or overproduced, in presence of suberin were involved in carbohydrate metabolism. Most of the proteins included in the lipid metabolism class have been detected in CSM. Apart from lipid metabolism proteins, other identified proteins, particularly two feruloyl esterases, may also actively participate in the breakdown of suberin architecture. Both feruloyl esterase genes were overexpressed between 30 to 340 times in the presence of suberin.ConclusionThis study demonstrated that the presence of suberin in S. scabiei growth medium induced the production of a wide variety of glycosyl hydrolases. Furthermore, this study has allowed the identification of extracellular enzymes that could be involved in the degradation of suberin, including enzymes of the lipid metabolism and feruloyl esterases.

Acquisition of amino acids by Lactobacillus delbrueckii subsp. bulgaricus 2038 when grown in the presence of casein

The acquisition of amino acids by Lactobacillus delbrueckii subsp. bulgaricus 2038 (Lb. bulgaricus 2038) when grown in the presence of bovine casein, the major protein in bovine milk, was investigated by examining the expression of genes related to proteolysis and amino acid biosynthesis. To support the growth on bovine casein, Lb. bulgaricus 2038 has to synthesise five kinds of amino acids de novo, as proteolysis from casein does not provide these. The incomplete hydrolysis in combination with amino acids biosynthesis may explain the slow growth of Lb. bulgaricus 2038 in a casein environment. Meanwhile, it was determined that Lb. bulgaricus 2038 uses different intracellular peptidases when grown in casein or whey medium, and initially yields the important amino acid glutamate from the C-terminal or N-terminal end of peptides imported into the cell.

Biochemical characterization of the apicoplast-targeted AAA+ ATPase ClpB from Plasmodium falciparum

ClpB is a molecular chaperone from the AAA+ superfamily of ATPases, which reactivates aggregated proteins in cooperation with the DnaK chaperone system. ClpB is essential for infectivity and in-host survival of a number of pathogenic microorganisms, but systematic studies on ClpB from pathogens have not been reported yet. We purified and characterized one of the two ClpB isoforms from the malaria parasite Plasmodium falciparum, PfClpB1. PfClpB1 is targeted to the apicoplast, an essential plastid organelle that is a promising anti-malaria drug target. PfClpB1 contains all characteristic AAA+ sequence motifs, but the middle domain of PfClpB1 includes a 52-residue long non-conserved insert. Like in most AAA+ ATPases, ATP induces self-association of PfClpB1 into hexamers. PfClpB1 catalyzes the hydrolysis of ATP and its ATPase activity is activated in the presence of casein and poly-lysine. Similar to Escherichia coli ClpB, PfClpB1 reactivates aggregated firefly luciferase, but the PfClpB1-mediated aggregate reactivation is inhibited in the presence of E. coli DnaK, DnaJ, and GrpE. The lack of effective cooperation between PfClpB1 and the bacterial DnaK system may arise from the Plasmodium-specific sequence of the ClpB middle domain. Our results indicate that the chaperone activity of PfClpB1 may support survival of Plasmodium falciparum by maintaining the folding status and activity of apicoplast proteins.

The effect of milk alpha-casein on the antioxidant activity of tea polyphenols

In this study, we report how the antioxidant capacities of major tea polyphenols are affected by their interactions with milk alpha-casein (milk protein) using three complimentary oxidation methods: ABTS+ radical cation scavenging, cyclic voltammetry and lipid peroxidation inhibition. We found that using the ABTS+ assays, the antioxidant activity of all polyphenols was lowered by 11–27% in the presence of caseins. Using cyclic voltammetry, the overall current measured at the electrode was decreased by the presence of the protein, from 21% to 61%. The peak potentials were also shifted to higher values varying from 13 to 41mV. However, using lipid peroxidation method, we noticed of the antioxidant activity of all the polyphenols changed (from 6% up to 75%) after the addition of alpha-casein. The results show using this method the larger gallate esters containing polyphenols epicatechingallate (ECG) and (epigallocatechingallate (EGCG) were less affected by the presence of casein than smaller polyphenols catechins (C), epicatechin (EC) and epicgallocatechine (EGC). Alpha-casein caused a small effect on the chain breaking antioxidant capacity of theaflavins as well. Therefore, casein has different effects on the overall antioxidant capacities of tea compounds depending on the methods used. We aim to understand those results with the types of protein–polyphenol interactions that take place in various settings and their effects on the antioxidant capacities of those compounds.

Recovery and examination of sculpture group Fugitive Slaveby V. Beklemishev

On the 26th of April 2010, while performing routine electrical work, a lost sculpture group of famous Russian sculptor Vladimir Beklemishev (1861–1920) titled ‘Fugitive Slave’ was found inside a wall of the Winter Palace in St. Petersburg, Russia on the landing of the staircase to the second floor. This sculpture was created under the influence of the anti-slavery novel “Uncle Tom's Cabin” by American author Harriet Beecher Stowe and was presented at the World's Columbian exposition in Chicago in 1893, devoted to the 400th anniversary of the discovery of America by Columbus. The sculpture was made from gypsum and coated with a covering that imitated bronze. At the moment of finding, the sculpture was heavily damaged and needed serious restoration, including repairing of the bronze imitation layer. This situation permitted us to do a detailed examination of the materials and techniques used in making this bronze-like covering. The sculpture was made by Beklemishev in Italy in 1891. At the time of writing, ‘Fugitive Slave’ has been restored to its former glory and can be admired in the State Hermitage museum in St. Petersburg, Russia. Studying the cross-sections of tiny fragments of bronze-like covering from different parts (bright and dark) showed that the coating was multilayered. Different parts of the covering also show large differences in structure. Pigment composition of each layer was investigated by SEM-EDS (Scanning Electron Microscopy-Energy Dispersive Spectroscopy). Relatively pure copper filings and scrapings were applied to imitate a solid bronze layer. The top thin layer, which imitated a bronze patina, was made of a copper arsenic paint. GC/MS analysis of the fatty acids showed the presence of drying oil. The presence of erusic acid, a biomarker, showed presence of the Brassicaceae seed oil. A small amount of pinaceous resin and dammar were discovered as well. The top thin layer, however, seemed to contain linseed oil (based on fatty acids ratios - A/P = 1.5; P/S=1.6). Besides that, the surfaces of the dark parts were covered with a very thin layer of beeswax. It is believed that this is the result of conservation treatment, rather than applied by Beklemishev himself. PCA analysis of the selected ion monitoring chromatograms of the proteinaceous materials showed the presence of egg in practically all layers of bright fragments and in the bottom layers of the dark fragments. According to literature, a mixture of drying oil, egg and resins was often used for priming in polychromic paints on stone in Italy. Since Beklemishev made ‘Fugitive Slave’ during his time there, it is possible that he used these materials. However, looking at the middle layers of the dark fragments, evidence for casein as proteinaceous ingredient was also found. Since the layers where casein was found are thicker, the presence of casein indicates that a casein-oil mixture was possibly applied as binding to get more pasty paint films. This way one may conclude that different binding materials were used for different layers. These analyses give a great insight into the way imitation of bronze of this sculpture was made and allow us to learn more about this specific technique.

High-pressure treatment of milk in industrial and pilot-scale equipments: effect of the treatment conditions on the protein distribution in different milk fractions

The effects of two different high-pressure (HP) equipments, operating at industrial- and pilot scales, and of the HP-release rate on the contents of non-sedimentable proteins and denatured whey proteins were investigated after treatments of skim milk—from 250 to 650 MPa. Non-sedimentable caseins and denatured whey proteins significantly increased with the pressure level. The industrial-scale equipment produced lower micellar disintegration than the pilot-scale equipment with similar degrees of whey protein denaturation. Ultracentrifugation supernatants obtained from skim milk at 100,000×g and 20 °C for 1 h were also HP-treated for comparative purposes, showing that, in skim milk, the presence of casein promoted the denaturation of whey proteins, although the extent of whey protein denaturation did not influence the release of casein to the soluble phase. Furthermore, most denatured whey proteins remained soluble after treatment in both equipments. In the pilot-scale equipment, the pressure-release rate influenced casein solubilization and whey protein denaturation.

Calcium Carbonate Crystallization in the Presence of Casein

Phosphoproteins have specific and prominent influences on mediating the crystallization of calcium carbonate. In this research, a new kind of calcium carbonate crystal with a novel self-organized spiky dumbbell-like superstructure was synthesized in the presence of one typical phosphoprotein-casein. A complex self-assembly process for the formation of the hierarchical superstructures in the presence of casein has been proposed. The effects of the concentration of calcium ion, the reaction time, and temperature are investigated. The results indicate that phosphate groups of casein play important roles in directing growth and self-assembly of hierarchical superstructures. Our studies may contribute to the understanding of the specific role of phosphoprotein in the biomineralization process. We also believe that our studies will provide new insights into controlling the structure and morphology of minerals under easily attainable reaction conditions in the presence of phosphoprotein.

Identification and partial characterization of extracellular aspartic protease genes from Metschnikowia pulcherrima IWBT Y1123 and Candida apicola IWBT Y1384.

The extracellular acid proteases of non-Saccharomyces wine yeasts may fulfill a number of roles in winemaking, which include increasing the available nitrogen sources for the growth of fermentative microbes, affecting the aroma profile of the wine, and potentially reducing protein haze formation. These proteases, however, remain poorly characterized, especially at genetic level. In this study, two extracellular aspartic protease-encoding genes were identified and sequenced, from two yeast species of enological origin: one gene from Metschnikowia pulcherrima IWBT Y1123, named MpAPr1, and the other gene from Candida apicola IWBT Y1384, named CaAPr1. In silico analysis of these two genes revealed a number of features peculiar to aspartic protease genes, and both the MpAPr1 and CaAPr1 putative proteins showed homology to proteases of yeast genera. Heterologous expression of MpAPr1 in Saccharomyces cerevisiae YHUM272 confirmed that it encodes an aspartic protease. MpAPr1 production, which was shown to be constitutive, and secretion were confirmed in the presence of bovine serum albumin (BSA), casein, and grape juice proteins. The MpAPr1 gene was found to be present in 12 other M. pulcherrima strains; however, plate assays revealed that the intensity of protease activity was strain dependent and unrelated to the gene sequence.

Identifying Microorganisms Able to Perform Biodegradation of Leather Industry Waste

Among the waste generated in leather processing, proteic and lipidic compounds are particularly dominant. Enzymes, like proteases and lipases, have an important role in biodegradation of collagen, keratin and fats in leather waste. Present investigation deals with isolation, selection and characterization of proteolytic and lipolytic microorganisms in order to perform biodegradation of waste from leather industry. The inoculum of microorganisms was sampled from old waste storage dump leather. The proteolytic microorganisms were isolated using screening method in presence of casein and gelatin substrate type, respectively. The microorganisms that secrete the lipolytic enzymes were isolated using medium that contained the Tween 80. These microorganisms identified by microscopic analysis can be used for improvement of waste leather biodegradation process.

Effect of milk thermal history on the recovery of TGF-β2 by acid precipitation of whey protein concentrates

The objective of the study was to characterize the effects of preheating of milk and of pasteurization steps during whey processing on the separation of transforming growth factor-beta 2 (TGF-β2) from whey protein concentrates (WPCs). Three heating conditions were applied to skimmed milk: no heating, 63 °C for 20 s and 68 °C for 20 s. The effect of pasteurizing liquid acid whey and liquid WPC was also assessed. Heating milk at 63 or 68 °C decreased TGF-β2 content of whey. A pasteurization treatment of whey at 72 °C for 15 s further decreased their TGF-β2 content. However, an additional pasteurization of WPCs significantly increased TGF-β2 only in samples from unheated milk. Acid precipitation of WPCs showed that cumulative heat treatments increased the amount of precipitate obtained, and that pH 4.5 was found to be optimal in terms of TGF-β2 content of precipitates. The highest TGF-β2 concentrations in acid precipitates (>10,000 pg.mg−1 solids) were obtained with a combination of heating milk at 63 °C for 20 s and pasteurization of whey at 72 °C for 15 s. It was found that, although whey obtained from raw milk represents the best source of TGF-β2, an appropriate selection of heat treatments of liquid whey and WPC improves the recovery of TGF-β2. The presence of casein and minor whey proteins in TGF-β2-enriched fractions underlines the occurrence of complex heat-induced interactions between TGF-β2 and other milk constituents.

The viability of the Lactobacillus paracasei IL2 and Lactobacillus plantarum IL3 strains in simulated gastrointestinal conditions

The viability maintenance of Lactobacillus paracasei IL2 and Lactobacillus plantarum IL3 strains in gastrointestinal conditions represents one of the most important characteristics regarding their use for obtaining probiotic products. The tests were performed with a cell suspension kept in 0.5% NaCl. The influences of pepsin (3 g/l) at pH values of 1.5, 2, 2.5 and 3.0, as well as of pancreatin (1 g/l) in the presence of bile salts (1.5, 2, 3 and 5 mg/ml) were determined. The influence of casein and mucin, in a concentration of 1 g/l, were also established in the aforementioned conditions. It was observed that casein presented a longer viability maintenance; a fact also confirmed by the calculation of the mathematical parameters of viability and mortality, when mucin was either used or not, especially in the case of gastric transit. The results proved that the tested strains maintained their viability even at pH between 1.8 and 2.0 and at an even higher concentration, of 2 mg/ml, of bile salts, but up to two hours as of the exposure to the conditions of the simulated small intestinal juice. Such results were also confirmed by the cumulated effect of the simulated gastric and small intestinal juice, the strains thus increasing their viability with an average of 15% in the presence of casein.

The effect of protein on the dissolution of phenytoin.

Ultrafiltration of a continuous flow system was used to follow the dissolution of phenytoin powder in buffered solutions of pH 1, 4 and 7.4. The presence of either human serum albumin (HSA) or casein caused changes in both the absolute solubility and the dissolution rate. Normal protein binding cannot be responsible for the effects noted. It would seem likely that within the diffusion layer a higher degree of protein binding occurs than is possible in the bulk aqueous solution. The drug solubilized in this way is then released in solution in a form that is at least metastable with respect to phenytoin in normal solution. The effect of protein on phenytoin dissolution may well affect the bioavailability of the drug.

Flocculation of Kaolinite Suspensions in Water by Coconut Cream Casein

The flocculation of kaolinite colloidal particles was carried out at pH = 6 in suspension of initial turbidity varying between 24 NTU and 102 NTU by a casein extracted from Cocos nucifera cream. During Jar-test essays, 90% to 99% of colloids were eliminated in the sediments. The optimal doses of casein used depend on the initial colloids concentrations of the suspension and were found to be 60 mg/L and 100 mg/L respectively for suspensions having turbidity of 24 NTU and 102 NTU. The corresponding residual turbidity are respectively 2.80 NTU and 10.22 NTU for clarified water. The structural analysis of the freeze-dried sediments by FTIR shows sharp adsorption bands at 1558 cm–1 and 1653 cm–1, indicating the presence of casein in the sediment. The flocculation process between the particles of kaolinite and the coconut casein is adsorption and bridging.

Self-assembly and characterization of Ca–Al–LDH nanohybrids containing casein proteins as guest anions

Casein, a natural biopolymer contained in milk, has been successfully intercalated into a Ca–Al–LDH host structure. Synthesis was performed by rehydration of tricalcium aluminate in the presence of casein. The resulting nanohybrids were characterized by powder X-ray diffraction (XRD), elemental analysis, infrared spectroscopy (IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Further experiments revealed that the single protein strains intercalate instead of the entire casein sub micelles, which are present in milk. Additionally, the pure phospho protein fractions α- and β-casein, which make up ∼80 wt% of total casein were isolated and intercalated into the Ca–Al–LDH host structure, yielding a biopolymer–inorganic hybrid material.

In vitro food–drug interaction study: Which milk component has a decreasing effect on the bioavailability of ciprofloxacin?

The purpose of the present work was developing an in vitro dissolution test to highlight the possible molecular background causing ciprofloxacin (CPFX)–milk interaction. The in vitro dissolution of CPFX from film-coated tablets (Ciprinol ® 500 mg) was examined at different pH values, simulating certain parts of the gastrointestinal tract, in the presence of water, low-fat milk, casein- or calcium enriched water. In order to determine the amount of dissolved CPFX, solid phase extraction sample preparation followed by high performance liquid chromatography coupled with mass spectrometry was applied. Comparing the dissolution efficiency values in various media, it can be concluded, that casein has a more pronounced effect on the absorbable amount of the antibiotic at each pH value studied, than calcium. In the case of concomitant intake of CPFX film-coated tablet and milk or other dairy products not only the complexation with calcium, but also the adsorption of CPFX on the surface of proteins decreases the absorbable amount of CPFX.

Oxidative cross-linking of casein by horseradish peroxidase and its impacts on emulsifying properties and the microstructure of acidified gel

The cross-linking of food proteins is an interesting topic of food science in recent years and served successfully as an approach to modify protein functional properties. In the presented work, horseradish peroxidase (HRP, EC 1.11.1.7) was used to oxidative cross-link casein in presence of H2O2. The cross-linking of casein was demonstrated by capillary zone electrophoresis analysis. The central composite design using response surface methodology was used to optimize cross-linking conditions of casein. The optimal cross-linking conditions of casein were as follows: the addition level of HRP was 4.73 mkat·g-1 proteins, temperature was 37°C and reaction time was 2.9 h when casein concentration and pH of reaction medium were fixed at 5% (w/w) and 9.5, respectively. Cross-linked casein was prepared with these optimal conditions and used to analyze its emulsifying activity index, emulsifying stability index and microstructure of acidified gel. The emulsifying activity index and emulsifying stability index of the cross-linked casein were enhanced about 10 and 6% compared to that of casein. The microstructure of acid-induced gel of the cross-linked casein observed by scanning electron microscopy was more compact and uniform than that of casein without cross-linking. Cross-linking of food proteins induced by horseradish peroxidase might serve as an alternative approach to modify functional property of the proteins.

A Food-Grade Enzyme Preparation with Modest Gluten Detoxification Properties

Background and AimsCeliac sprue is a life-long disease characterized by an intestinal inflammatory response to dietary gluten. A gluten-free diet is an effective treatment for most patients, but accidental ingestion of gluten is common, leading to incomplete recovery or relapse. Food-grade proteases capable of detoxifying moderate quantities of dietary gluten could mitigate this problem.MethodsWe evaluated the gluten detoxification properties of two food-grade enzymes, aspergillopepsin (ASP) from Aspergillus niger and dipeptidyl peptidase IV (DPPIV) from Aspergillus oryzae. The ability of each enzyme to hydrolyze gluten was tested against synthetic gluten peptides, a recombinant gluten protein, and simulated gastric digests of whole gluten and whole-wheat bread. Reaction products were analyzed by mass spectrometry, HPLC, ELISA with a monoclonal antibody that recognizes an immunodominant gluten epitope, and a T cell proliferation assay.ResultsASP markedly enhanced gluten digestion relative to pepsin, and cleaved recombinant α2-gliadin at multiple sites in a non-specific manner. When used alone, neither ASP nor DPPIV efficiently cleaved synthetic immunotoxic gluten peptides. This lack of specificity for gluten was especially evident in the presence of casein, a competing dietary protein. However, supplementation of ASP with DPPIV enabled detoxification of moderate amounts of gluten in the presence of excess casein and in whole-wheat bread. ASP was also effective at enhancing the gluten-detoxifying efficacy of cysteine endoprotease EP-B2 under simulated gastric conditions.ConclusionsClinical studies are warranted to evaluate whether a fixed dose ratio combination of ASP and DPPIV can provide near-term relief for celiac patients suffering from inadvertent gluten exposure. Due to its markedly greater hydrolytic activity against gluten than endogenous pepsin, food-grade ASP may also augment the activity of therapeutically relevant doses of glutenases such as EP-B2 and certain prolyl endopeptidases.