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At least 1,405 records · Page 78Linked to original sources
PubMed1998

Sensitization to cow's milk proteins during refeeding of guinea pigs recovering from polydeficient malnutrition.

We have previously shown that milk sensitization aggravates intestinal dysfunction in the malnourished guinea pigs, suggesting that it may also impair the recovery from malnutrition. To test this hypothesis, the growing guinea pigs were malnourished by feeding only maize for 7 d and then were refed for 21 d with a balanced diet containing either intact or hydrolyzed cow's milk proteins. The control animals received the hydrolyzed milk protein diet for 28 d. After an initial period of total inhibition of growth owing to maize, guinea pigs gained weight regularly, with both balanced diets, and there was no evidence of mucosal damage at the end of the refeeding period. However, refeeding with intact milk proteins induced milk sensitization, which was demonstrated on the systemic level by the presence of anti-beta-lactoglobulin IgG1 antibodies, and on the local level by the intestinal anaphylaxis measured by the increase in short circuit current induced by beta-lactoglobulin (16.4 +/- 2.6 microA/cm2) in jejunal segments mounted in Ussing chambers. Such an immune sensitization was associated with impaired intestinal permeability, as both the ionic conductance (21.0 +/- 1.6 versus 14.6 +/- 0.7 mS/cm2) and the transepithelial fluxes of horseradish peroxidase (537 +/- 203 versus 152 +/- 28 ng/h x cm2) were significantly increased in guinea pigs refed with the intact milk proteins compared with controls. In contrast, there was no difference in intestinal permeability between controls and guinea pigs refed with the hydrolyzed milk protein diet. These data show that sensitization to cow's milk proteins can develop in guinea pigs recovering from severe malnutrition and may impair full intestinal repair.

Anaphylaxis↗
PubMed1997

Interaction of mercury with human and bovine milk proteins.

The interaction of inorganic mercury with human and bovine milk proteins was studied. Gel filtration chromatography of skimmed milk and whey incubated with mercury showed that, in human milk, mercury was mainly bound to caseins, while a low proportion was bound to albumin. In bovine milk, mercury was associated with two protein fractions, caseins and beta-lactoglobulin. Furthermore, it was shown by electrophoresis that mercury induced the formation of dimers of beta-lactoglobulin. Thus, in both human and bovine milk, mercury possessed greater ability to interact with milk proteins than to the low-molecular-weight substances. However, the pattern of mercury distribution was different between the milk of these two species.

Animals↗
PubMed1997

Effects of lecithin addition in oil or water phase on the stability of emulsions made with whey proteins.

The effects of lecithin addition in oil or water phase on the stability of oil-in-water emulsions made with 0.1 wt% whey protein and 10 wt% n-tetradecane at neutral and acidic pH were studied by monitoring the gravitational creaming and phase separation. The effects of lecithin addition on the interfacial behavior of beta-lactoglobulin were also studied to compare with the results of emulsion stability. At neutral pH, crude phosphatidylcholine (PC) from egg yolk or soybean increased the stability of the emulsion made with protein and lowered the interfacial tension of protein films more effectively than pure egg PC. A more remarkable effect on both the emulsion stability and the interfacial tension was found when crude PC was added in the oil phase rather than in the water phase. The purity of lecithins and the way to add them are suggested to be very important to make a stable emulsion with protein. On acidic pH (4.5 or 3.0), the increased creaming or phase separation in a whey protein-stabilized emulsion, but the lowered interfacial tension of beta-lactoglobulin films, were found upon the addition of pure or crude PC in oil or water phase. These results suggest that in acidic pH, densely packed films may be formed on a planar oil-water interface, but not on adsorbed layers around oil droplets in an emulsion.

Animals↗
PubMed2003

Solid-phase reducing agents as alternative for reducing disulfide bonds in proteins.

Disulfide reduction of Kluyveromyces lactis and Aspergillus oryzae beta-galactosidases and beta-lactoglobulin was assessed. Reduction was performed using one of two thiol-containing agents: dithiothreitol (DTT) or thiopropyl-agarose with a high degree of substitution (1000 micromol of SH groups/g of dried gel). Both reductants allowed an increase of three- (for K. lactis beta-galactosidase) and fourfold (for A. oryzae beta-galactosidase) in the initial content of SH groups in the lactases. Nearly sevenfold fewer micromoles of SH groups per milligram of protein were needed to perform the reduction of K. lactis beta-galactosidase with thiopropyl-agarose than for the same reduction with DTT. However, for A. oryzae beta-galactosidase, nearly twice as many micromoles of SH groups per milligram of protein were needed with thiopropylagarose than with DTT. Disulfide bonds in beta-lactoglobulin were not accessible to thiopropyl-agarose, since this reduction was only possible in the presence of 6 M urea. These results proved that highly substituted thiopropyl-agarose is as good a reducing agent as DTT, for the reduction of disulfide bonds in proteins. Moreover, excess reducing agent was very simply separated from the reduced protein by filtration, making it easier to control the reaction and providing reduced protein solutions free of reductant. All these advantages substantially cut down the time required and therefore the cost of the overall process.

Aspergillus oryzae↗
PubMed2001

Controlled hydrolysis of cheese whey proteins using trypsin and alpha-chymotrypsin.

This study examined the production of protein hydrolysates with controlled composition from cheese whey proteins. Cheese whey was characterized and several hydrolysis experiments were made using whey proteins and purified beta-lactoglobulin, as substrates, and trypsin and alpha-chymotrypsin, as catalysts, at two temperatures and several enzyme concentrations. Maximum degrees of hydrolysis obtained experimentally were compared to the theoretical values and peptide compositions were calculated. For trypsin, 100% of yield was achieved; for alpha-chymotrypsin, hydrolysis seemed to be dependent on the oligopeptide size. The results showed that the two proteases could hydrolyze beta-lactoglobulin. Trypsin and alpha-chymotrypsin were stable at 40 degrees C, but a sharp decrease in the protease activity was observed at 55 degrees C.

Cheese↗
PubMed2005

Anaphylaxis in a milk-allergic child after ingestion of soy formula cross-contaminated with cow's milk protein.

In this report we describe a 9-month-old boy with severe persistent asthma and documented cow's milk allergy (presented with eczema and severe systemic reactions) who had an anaphylactic reaction to a soy formula contaminated with cow's milk protein. Quantitative enzyme-linked immunosorbent assay analysis revealed trace quantities of beta-lactoglobulin in the offending soy formula as well as the dry powder. The patient did not demonstrate clinical reactivity to soy protein (negative challenge, tolerated pure soy formula well). Cross-contamination of the offending soy formula was presumed to have occurred during food manufacturing. This case demonstrates that trace quantities of cow's milk protein can elicit severe systemic reactions in highly milk-allergic individuals. This infant ingested the equivalent of 0.4 mL of cow's milk from the soy formula as documented by an immunoassay for beta-lactoglobulin. This highlights the ease with which cross-contamination can occur during food processing and reinforces the need for better quality control.

Anaphylaxis↗
PubMed1994

The effect of proctocolectomy on serum antibody levels against cow's milk proteins in patients with chronic ulcerative colitis, with special reference to liver changes.

BACKGROUND: The levels of antibodies against cow's milk proteins in ulcerative colitis (UC) were used to study whether mucosal inflammation leads to immune recognition, as a marker of enhanced permeability, of dietary proteins. A further purpose was to study the effect of proctocolectomy on the serum antibody levels against cow's milk proteins and their relation to biochemical and histologic liver abnormalities associated with ulcerative colitis. METHODS: Serum antibody levels against six cow's milk proteins, alpha-casein, alpha-lactalbumin (LA), beta-lactoglobulin A (LGA), beta-lactoglobulin B (LGB), bovine serum albumin (BSA), and whole milk powder (MP) were determined before and after (mean, 24 months) proctocolectomy in 15 patients with ulcerative colitis. Simultaneously, serum liver enzymes were analyzed. A liver biopsy specimen was also obtained at proctocolectomy. RESULTS: Before proctocolectomy IgA antibody levels were significantly increased against all antigens except BSA. Increased levels of IgM antibodies against LGA, LGB, and BSA were also detected. IgG antibodies were significantly increased only against LGA. After proctocolectomy IgA and IgM antibody levels decreased significantly (p < 0.05) against LGA, LGB, and LA, whereas IgG antibodies increased significantly (p < 0.01). In the patient group with abnormal liver histology (n = 9) the IgA antibodies to all cow's milk proteins were significantly higher (p < 0.02) than in the group with normal liver histology both before and after proctocolectomy. The IgA antibody levels showed a significant positive correlation with alanine amino-transferase and gamma-glutamyltransferase (r value from 0.460 to 0.721, p value from < 0.05 to < 0.01), but not with alkaline phosphatase. CONCLUSIONS: These results suggest that the inflamed mucosa in UC allows the antigenic contents of the bowel to escape. Proctocolectomy alters the antibody levels against certain milk proteins, which may serve as a model to suggest that proctocolectomy, probably by eliminating inflammation, may have positive effects by reducing the foreign pathogenic antigen and immune complex load.

Adult↗
PubMed2004

Structural analysis of a new anti-hypertensive peptide (beta-lactosin B) isolated from a commercial whey product.

Angiotensin-converting enzyme (ACE) inhibitory activities and anti-hypertensive activities in spontaneously hypertensive rats (SHR) of 12 kinds of commercial peptides of food additive grade were measured. Four peptide products derived from milk proteins showed strong anti-hypertensive activities (>-18.0 mm Hg). A sample of WE80BG derived from whey proteins showed the strongest anti-hypertensive activity (-21.2 +/- 16.9 mm Hg) with a medium level of ACE inhibitory activity (53.6%), and it was subjected to hydrophobic and gel filtration chromatography. From the low molecular weight fraction, an anti-hypertensive peptide was isolated by using reversed-phase HPLC, and it was found to be a tetrapeptide, alanine-leucine-proline-methionine (Ala-Leu-Pro-Met, ALPM), the origin of which was estimated to be beta-lactoglobulin f 142 to 145. At 8 h after oral administration of ALPM in SHR, systolic blood pressure was significantly decreased (-21.4 +/- 7.8 mm Hg), but the IC50 value (concentration of peptide needed to inhibit 50% of the ACE activity) of ALPM was not so high. We named the Ala-Leu-Pro-Met "beta-lactosin B." This peptide is the second anti-hypertensive peptide found from beta-lactoglobulin. Because WE80BG containing ALPM was also found to show the strongest anti-hypertensive activity (-24.5 +/- 10 mm Hg) at 8 h after oral administration in SHR, WE80BG would be suitable for application to the development of a new food expected to have anti-hypertensive effects.

Amino Acids↗
PubMed2005

Yield and aging of Cheddar cheeses manufactured from milks with different milk serum protein contents.

Whey proteins in general and specifically beta-lactoglobulin, alpha-lactalbumin, and immunoglobulins have been thought to decrease proteolysis in cheeses manufactured from concentrated retentates from ultrafiltration. The proteins found in whey are called whey proteins and are called milk serum proteins (SP) when they are in milk. The experiment included 3 treatments; low milk SP (0.18%), control (0.52%), and high milk SP (0.63%), and was replicated 3 times. The standardized milk for cheese making of the low milk SP treatment contained more casein as a percentage of true protein and more calcium as a percentage of crude protein, whereas the nonprotein nitrogen and total calcium content was not different from the control and high SP treatments. The nonprotein nitrogen and total calcium content of the milks did not differ because of the process used to remove the milk SP from skim milk. The low milk SP milk contained less free fatty acids (FFA) than the control and high milk SP treatment; however, no differences in FFA content of the cheeses was detected. Approximately 40 to 45% of the FFA found in the milk before cheese making was lost into the whey during cheese making. Decreasing the milk SP content of milk by 65% and increasing the content by 21% did not significantly influence general Cheddar cheese composition. Higher fat recovery and cheese yield were detected in the low milk SP treatment cheeses. There was more proteolysis in the low milk SP cheese and this may be due to the lower concentration of undenatured beta-lactoglobulin, alpha-lactalbumin, and other high molecular weight SP retained in the cheeses made from milk with low milk SP content.

Animals↗
PubMed1976

Composition of the milks of dairy cattle. II. Ash, calcium, magnesium, and phosphorus.

Milks from commercial dairy herds in Southeastern Pennsylvania were analyzed for ash, calcium, magnesium, and phosphorus. Milk samples were from single milkings of 151 healthy purebred cows in midlactation. The data represent market milk composition. Average values for all animals were ash .78%, calcium 1.25 g/liter, magnesium .11 g/liter, and phosphorus 1.14 g/liter. The data also were grouped and analyzed by breed and beta-lactoglobulin phenotype. Breeds differed in all inorganic components with 18 to 33 cows per breed. No differences in ash, calcium, magnesium, or phosphorus were significant when the data were grouped by beta-lactoglobulin phenotype.

Animals↗
PubMed1976

Effect of psychrotrophic bacteria from raw milk on milk proteins and stability of milk proteins to ultrahigh temperature treatment.

The effects of psychrotroph growth in raw milk on proteins of mils and on the response of milk proteins to heat treatments with ultrahigh temperature were studied. Ten gram-negative psychrotrophs isolated from raw milk readily attacked raw milk proteins. Kappa- and beta-casein were most susceptible although some of the isolates also attacked the whey proteins. Detectable proteolysis did not require large psychrotroph populations. A 10 to 20% decrease in kappa-casein during 2 days at 5 C accompanied growth of one isolate to a population of only 10,000/ml. Growth of psychrotrophs in raw milk predisposed the proteins to deleterious effects of ultrahigh temperature treatments. Ultrahigh temperature treatment by direct steam injection had little effect on raw milk caseins and decreased alpha-lactalbumin and beta-lactoglobulin by 21% and 34%, respectively. Milk that had undergone proteolysis exhibited decreased detectable kappa-, beta-, and alphas-caseins and increased loss of beta-lactoglobulin as a result of ultrahigh temperature treatment. Milk suffering extensive kappa-casein degradation coagulated during ultrahigh temperature treatment. Coagulation during or shortly after heating increased with severity of heat treatment and size of psychrotroph population.

Animals↗
PubMed1980

Extracellular amino acid effects on milk protein synthesis and intracellular amino acid pools with bovine mammary cells in culture.

Increases in free intracellular amino acids are associated with increased protein synthesis. Responses in synthesis of beta-casein and beta-lactoglobulin and of intracellular amino acid pools to graded concentrations of amino acids in the medium were observed. Mammary tissue from two Holstein cows was dispersed and cultured for 18 h with Eagle's minimal essential medium containing 1, 3, 5, or 7 times the basic concentration of amino acids. Synthesis of beta-casein and beta-lactoglobulin increased with concentration of amino acids in the medium. Intracellular pools of amino acids not provided by the medium (serine, proline, alanine, glycine, glutamic acid, ornithine) generally decreased with increased concentrations of amino acids in the medium, the exception being ornithine which increased with extracellular amino acids. Lysine, histidine, tyrosine, leucine, valine, phenylalanine, isoleucine, arginine, and threonine intracellular pools increased with increased amino acids in medium. Intracellular cystine responded with a small linear increase to increased amino acids in the medium, while intracellular tryptophan and methionine did not respond, indicating potential limitations from these amino acids.

Amino Acids↗
PubMed1982

Protein composition of whey from subclinical mastitis and effect of treatment with levamisole.

Subclinical mastitis caused a rise in the noncasein protein concentration of milk. This mainly was caused by an increase in the concentration of serum albumin and immunoglobulin derived from blood. In most cases, the concentration of the major whey proteins beta-lactoglobulin and alpha-lactalbumin decreased. This decrease can be attributed to both inflammatory damage of mammary secretory tissues and destruction of blood-milk permeability barriers. When used orally, levamisole reduced leukocyte count and intramammary pathogens. Although changes of concentration were least for relative amounts of beta-lactoglobulin, serum albumin, and immunoglobulin, we observed enhanced alpha-lactalbumin production and simultaneous reduction of the total whey protein as mastitis score decreased. In normal quarter milk, the relative amount of immunoglobulin increased with levamisole. This suggests there was increased transport of immunoglobulin to aid udder health.

Animals↗
PubMed1992

Associations between milk protein polymorphisms and milk production traits.

Associations between milk protein genotypes and milk production traits were estimated from 6803 first lactation records. Exact tests of associated hypotheses and unbiased estimates of genotype effects were from an animal model. Milk protein genotype effects were estimated using a model in which each milk protein gene was analyzed separately (single-gene analysis) and a model in which all milk protein genes were analyzed simultaneously (multigene analysis). The results of the two models indicate that some effects ascribed to certain milk protein genes in the single-gene analysis are not effects of the milk protein gene itself but of linked genes. Results from this study and from literature indicate that the kappa-casein gene or a very closely linked gene affects protein percentage, and the beta-lactoglobulin gene or a very closely linked gene affects fat percentage. Furthermore, effects of beta-casein genotypes on milk production, fat percentage, and protein yield were significant, and beta-lactoglobulin genotypes had significant effects on milk production and protein yield. It is less clear whether those effects are due to effects of milk protein genes themselves or to effects of linked genes.

Animals↗
PubMed1993

The secondary structure of milk proteins and their biological function.

A brief overview is given of the methods of determining and predicting secondary structure in proteins. The secondary structures of the milk serum proteins, lactoferrin, alpha-lactalbumin, lysozyme, and beta-lactoglobulin, as determined by x-ray crystallography, are compared with the results of a joint prediction method. This comparison evaluates critically the degree of success achieved and helps define what can reasonably be expected from a prediction in the absence of a known structure. The value of supplementary information from spectroscopic methods and the use of templates and sequence information from related proteins in improving the confidence of predictions are illustrated. One point that emerges is the general overprediction of helix content by the joint prediction method such that, for an all-beta protein such as beta-lactoglobulin, the method of Garnier, Osguthorpe, and Robson, applied with the correctly selected decision constants, provides a somewhat better approach. Secondary structure of the caseins can be predicted with less confidence than for globular proteins, and the results should be interpreted as evidence of a propensity to form transient secondary structures of the indicated type in view of the generally open and flexible conformation of caseins in solution.

Amino Acid Sequence↗
PubMed1998

Structural analysis of new antihypertensive peptides derived from cheese whey protein by proteinase K digestion.

Whey protein was digested with one of seven kinds of proteases at 37 degrees C (trypsin, proteinase K, actinase E, thermolysin, or papain) or at 25 degrees C (pepsin or chymotrypsin) for 24 h. The digested samples were assayed for the inhibitory activity of angiotensin-converting enzyme and for changes in the systolic blood pressure caused in spontaneously hypertensive rats after gastric intubation. The strongest depressive effect on the systolic blood pressure (-55 mm Hg) was observed at 6 h after gastric intubation of the whey protein that was digested by proteinase K. Finally, six peptides were chromatographically isolated from the proteinase K digest by a combination of hydrophobic reversed-phase HPLC and gel filtration. The amino acid sequences and their origins were clarified as follows: Val-Tyr-Pro-Phe-Pro-Gly [beta-casein (CN); f 59-64], Gly-Lys-Pro (beta 2-microglobulin; f 18-20), Ile-Pro-Ala (beta-lactoglobulin; f 78-80), Phe-Pro (serum albumin; f 221-222; beta-CN, f 62-63, f 157-158, and f 205-206), Val-Tyr-Pro (beta-CN; f 59-61), and Thr-Pro-Val-Val-Val-Pro-Pro-Phe-Leu-Gln-Pro (beta-CN; f 80-90). Chemical synthesis of these six peptides confirmed that all peptides, except an undecapeptide, have antihypertensive activity in spontaneously hypertensive rats. The synthetic tripeptide Ile-Pro-Ala, originating from beta-lactoglobulin, showed the strongest antihypertensive activity (-31 mm Hg).

Amino Acid Sequence↗
PubMed1975

[The lysis of proteins with cyanogen bromide (author's transl)].

Bovine beta-lactoglobulin-AB was split with cyanogen bromide, and the reaction mixture was analyzed by countercurrent distribution, gel chromatography and finally, chromatography on phosphocellulose. In addition to the previously described splitting products, we obtained three more minor products, with yields of 8, 15 and 25%. The analytical data indicate that these were formed by lysis C-terminal from the tryptophan-19 and the tryptophan-61 of beta-lactoglobulin. The result is discussed.

Amino Acids↗
PubMed2001

Identification of whey proteins in tradional Bulgarian yougurt.

Functional foods hold a great promise for future trends in human nutrition. Consumption of milk and milk products have a pronounced probiotic effects together with the expected modification of allergenic properties of milk due to the process of fermentation. The proteolytic system of lactic acid bacteria consists a cell wall bound proteinase and several intracellular peptidases, and can contribute to the liberation of bioactive peptides. Food-derived bioactive peptides are claimed to be health enhancing components which can be used for functional food. In our study we focused our attention on beta-lactoglobulin and alpha-lactalbumin in early stages of yogurt fermentation of traditional Bulgarian products. Biochemical techniques were used to measure the concentration of these two whey proteins during fermentation. At a result of the done study alteration in the concentration of beta-lactoglobulin and alpha-lactalbumin were detected. The studied proteolytic activity of the strains, used in the fermentation process confirmed the received results.

Fermentation↗