scholarly journals Acid gelation of colloidal calcium phosphate-depleted preheated milk

2009 ◽  
Vol 89 (3-4) ◽  
pp. 335-348 ◽  
Author(s):  
Marie-Hélène Famelart ◽  
Géraldine Gauvin ◽  
Denis Pâquet ◽  
Gérard Brulé
Keyword(s):  
Calcium Phosphate ◽  
Colloidal Calcium Phosphate ◽  
Acid Gelation

Exceptional preservation in the Jurassic of Osteno

1985 ◽  
Vol 311 (1148) ◽  
pp. 171-180 ◽  
Keyword(s):  
Calcium Phosphate ◽  
Organic Material ◽  
Soft Tissues ◽  
Taxonomic Diversity ◽  
Cellular Level ◽  
Metasomatic Process ◽  
Exceptional Preservation ◽  
Sea Bottom ◽  
Colloidal Calcium Phosphate ◽  
Sediment Interface

The Sinemurian deposit of Osteno, discovered in 1964, is remarkable for the exceptional preservation of its fossils. They are almost exclusively non-calcareous organisms such as fishes, crustaceans, polychaetes and nematodes. Their exceptional fossilization is due to a metasomatic process implying a molecule-for-molecule replacement of the organic material by colloidal calcium phosphate, a process that has permitted the preservation of the soft tissues of the organisms in some cases even to cellular level. The Osteno deposit formed on a poorly oxygenated sea bottom inhabited by fauna with a low taxonomic diversity, in some cases monotypic. Infaunal organisms are not found in the deposit since the H 2 S-O 2 boundary was probably situated slightly below the water-sediment interface.

Salt distribution between the colloidal and soluble phases of ewes' milk

1986 ◽  
Vol 53 (3) ◽  
pp. 353-358 ◽  
Author(s):  
Anna Polychroniadou ◽  
Anna Vafopoulou
Keyword(s):  
Calcium Phosphate ◽  
Molar Ratio ◽  
Strong Positive Correlation ◽  
Strong Negative Correlation ◽  
Stage Of Lactation ◽  
Colloidal Calcium Phosphate ◽  
Soluble Phase ◽  
Breed Differences ◽  
Salt Distribution ◽  
Main Factor

SUMMARYEwes' milk from two breeds of Greek sheep, Karagouniki and Serron, was analysed throughout mid and late lactation to investigate the salt distribution between colloidal and soluble phases. Separation of the phases was obtained by centrifugation at 48000 g. Effect of stage of lactation was significant only for total Mg in both breeds (P < 0·05) and for colloidal citrate in Serron ewe milk (P < 0·01). Breed differences were not significant (P < 0·05), except for colloidal casein.In the colloidal phase there was a strong positive correlation of casein with Ca and P, but correlation with Mg was poor. Molar sums of [Ca + Mg] and [P + Cit] were also significantly correlated. The Ca to P molar ratio averaged 2·00 and was higher than that reported for cows' milk. The inclusion of Mg as well as citrate in the colloidal calcium phosphate is indicated. In the aqueous phase there was a strong negative correlation of Ca with pH and a positive one with citrate. Correlation with phosphate was less. It seems that citrate is the main factor influencing Ca concentration in the soluble phase.

Effect on the composition and properties of casein micelles of interaction with ionic materials

1982 ◽  
Vol 49 (1) ◽  
pp. 87-98 ◽  
Author(s):  
Margaret L. Green
Keyword(s):  
Calcium Phosphate ◽  
Inorganic Phosphate ◽  
Casein Micelles ◽  
Low Concentrations ◽  
Colloidal Calcium Phosphate ◽  
Ionic Materials ◽  
Mean Size ◽  
Charge Concentration ◽  
The Mean ◽  
Micelle Hydration

SummaryThe effect on the composition and properties of casein micelles of the binding of ionic materials which accelerate the coagulation of milk on rennet treatment, was investigated. When considered in terms of their relative charge concentration, all the materials tested caused similar effects. The casein, inorganic phosphate and Ca contents of the micelles increased slightly. Micelle hydration decreased as additive binding increased. Casein and Ca dissociation on cooling increased at low concentrations of bound material, then progressively decreased at higher concentrations. The mean size of micelles and their electrophoretic mobility was little affected by bound ionic materials. The aggregation of the casein complexes in colloidal calcium phosphate-free milk was markedly increased by adding ionic materials, the efficiencies of these additives paralleling their efficiencies in accelerating the coagulation of milk by rennet. The results suggested that the ionic materials were bound in the interior of the casein micelles and promoted aggregation after rennet treatment by shielding charged groups, thus increasing the micellar hydrophobicity.

Mode of binding of ionic materials to casein micelles

1982 ◽  
Vol 49 (1) ◽  
pp. 99-105 ◽  
Author(s):  
Margaret L Green
Keyword(s):  
Calcium Phosphate ◽  
Binding Sites ◽  
Hydrophobic Interactions ◽  
Casein Micelles ◽  
Phosphate Moiety ◽  
Colloidal Calcium Phosphate ◽  
Ionic Materials ◽  
Milk Coagulation

SUMMARYThe proportion of materials which adsorb to casein micelles and accelerate milk coagulation, and remain bound on dilution of the micelle suspension with milk dialysate was determined. This was higher than expected from the postulate that equilibration took place between the solution and many equivalent binding sites on the micelle. This suggests that binding involved either or both hydrophobic interactions and multipoint attachment to charged groups. The location of the additive binding sites in the micelle was investigated using models Na caseinate and hydroxyapatite at pH 6·6. Materials which accelerated coagulation bound to either or both models. Those with the greatest effect on milk coagulation probably bound primarily to the casein rather than to the colloidal calcium phosphate moiety of casein micelles.

Heat stability of milk: influence of colloidal calcium phosphate and β-lactoglobulin

1975 ◽  
Vol 42 (3) ◽  
pp. 427-435 ◽  
Author(s):  
P. F. Fox ◽  
M. C. T. Hoynes
Keyword(s):  
Calcium Phosphate ◽  
Fold Increase ◽  
Heat Stability ◽  
Protein Charge ◽  
Ph Values ◽  
Colloidal Calcium Phosphate ◽  
Maximum Stability ◽  
Ph Range ◽  
Ph Curve ◽  
Β Lactoglobulin

SummaryReduction of the level of colloidal calcium phosphate (CCP) progressively increased the heat stability of milk at pH values <~7·0 and increased the pH of maximum stability. Removal of 40% CCP also stabilized the system at the pH of minimum stability, but removal of ≥60% CCP rendered milk very unstable at pH values >7·2, an effect not offset by a 4-fold increase in κ-casein concentration. Doubling CCP had a slight destabilizing effect in the pH range 6·5–7·5.Addition of β-lactoglobulin to serum protein-free casein micelles had a marked destabilizing effect at pH values > ~6·8, but increased stability in the pH range 6·4–6·8. β-Lactoglobulin had a similar and more apparent effect on the heat stability of Na caseinate dissolved in milk diffusate.It is suggested that rather than being a stabilizing factor responsible for the maximum in the heat stability-pH curve, the true effect of β-lactoglobulin is to shift the curve to more acid pH values (reason unknown) and to sensitize the caseinate system to heat-induced Ca phosphate precipitation at pH values > ~7·0. Low stability at ~pH 7·0 introduces an apparent maximum in the heat stability-pH curve at ~pH 6·8, but this has no independent existence. At pH values >7·2, increased protein charge more than off-sets the influence of heat-precipitated CCP and stability again increases in micellar but not in soluble casein systems.

Phosphopeptides interacting with colloidal calcium phosphate isolated by tryptic hydrolysis of bovine casein micelles

1996 ◽  
Vol 63 (3) ◽  
pp. 405-422 ◽  
Author(s):  
Valerie Gagnaire ◽  
Alice Pierre ◽  
Daniel Molle ◽  
Joelle Leonil
Keyword(s):  
Calcium Phosphate ◽  
Reversed Phase ◽  
Ion Source ◽  
Mass Spectrometry Analysis ◽  
Casein Micelles ◽  
Spectrometry Analysis ◽  
Peptide Fraction ◽  
Colloidal Calcium Phosphate ◽  
Hydrolysis Of ◽  
Tryptic Hydrolysis

SummaryAfter extended tryptic hydrolysis of large bovine casein micelles, a mineral-rich peptide fraction was recovered by ultracentrifugation. Its mineral part contained 72% of the colloidal Ca and 49% of the colloidal Pi originally present in the native micelle. Colloidal nitrogenous components were also present, amounting to 27% of the original N content. They contained most of the phosphopeptides and 82% of the micellar phosphoseryl residues. These tryptic peptides were characterized by reversed-phase HPLC on-line electrospray ion source–mass spectrometry analysis. Among the peptides produced 14 phosphopeptides were identified: αs2-CN(l–24), αs2-CN(1–21), αs1-CN(43–79), αs1-CN(35–79)7P, αs1-CN(35–79)8P, αs1-CN(37–79), αs1-CN(104–119), αs1-CN(104–124), β-CN(1–25), β-CN(1–28), β-CN(1–29), β-CN(30–97), β-CN(33–97) and β-CN(29–97). The proportion of the phosphopeptides interacting with colloidal calcium phosphate was correlated with their relative content of phosphoserine residues, since phosphopeptides containing more than four phos-phoserine residues were consistently present within this fraction. It also appeared that other types of peptides, some of them hydrophobic in nature, were also partly or completely present within the colloidal fraction, including αs1-CN(91–100), αs1-CN(152–193), αs1-CN(23–34), αs1-CN(125–193), αs1-CN(125–199), β-CN(177–209), β-CN( 184–209), β-CN(114–169) and β-CN(108–169). Their possible involvement in the micellar backbone is discussed.

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