The colloidal phosphate of milk: II. Influence of citrate

Pyne, G. T.; McGann, T. C. A.

doi:10.1017/s0022029900010074

Cited by 159 publications

(78 citation statements)

References 15 publications

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“…They reported that the typical sub-structure of natural micelles was observed in an artificial casein micelle contammg citrate as well as calcium and phosphate by means of electron microscopy, whereas such a structure was not apparent in artificial casein micelles containing no citrate. According to Pyne and McGann,12) about 11 % of the citrate in milk occurs in the colloidal phase, and is present as colloidal calcium phosphate citrate complex. When calcium phosphate is precipitated in the presence of citrate, citrate is co-precipitated.…”

Section: Discussionmentioning

confidence: 99%

Role of Individual Milk Salt Constituents in Cross-linking by Colloidal Calcium Phosphate in Artificial Casein Micelles

Aoki

Kawahara

Kako

et al. 1987

Agricultural and Biological Chemistry

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Artificial casein micelles were prepared at a casein concentration of 2.5% with various salt compositions, and the content of the casein aggregates cross-linked by colloidal calcium phosphate (CCP) was determined by high-performance gel chromatography on a TSK-GEL G4000SW column, using 6 M urea-simulated milk ultrafiltrate as the effluent. When phosphate was incorporated into calcium caseinate micelle systems, the casein aggregates cross-linked by CCP appeared. In these micelle systems, not all of the formed calcium phosphate seemed to participate in cross-linking, because part of the calcium phosphate was in the urea-insoluble form. When micelles were prepared at 30 mM calcium and 22 mM phosphate, the content of the casein aggregates crosslinked by CCP was higher in the presence of 10mM citrate than in the absence of citrate. The precipitate of calcium phosphate formed in the presence of citrate had cross-linking ability, whereas the precipitate formed in the absence of citrate did not. It is suggested that citrate plays an important role in cross-linking by CCP. Magnesium phosphate alone had no cross-linking ability. Magnesium increased the amount of calcium phosphate to promote cross-linking. 817Bovine casein micelles are highly hydrated and roughly spherical colloidal particles of 20 ~ 600 nm in diameter, which are heterogeneous in constititution. 1 ) They are composed of 93% casein and 7% inorganic constituents.The main casein constituents are iXs!-' iXs2 -' f3-and K-casein, in the proportions of about 3 : 0.8 : 3 : 1. The main constituent of inorganic matter is calcium phosphate, called colloidal calcium phosphate (CCP). CCP plays an important role in maintaining the integrity of casein micelles, because these micelles are disintegrated into submicelles when CCP is removed. 2 ) Although Schmidt!) has recently proposed a new model for the structure of casein micelles in which the micelles are composed of submicelles held together by means of CCP, no experimental evidence for the linkage between CCP and casein has been presented. In the previous study,3) we separated the casein aggregates cross-linked by CCP from reduced casein micelles by means of high-performance gel chromatography on a TSK-GEL G4000SW column, using 6 M urea-simulated milk ultrafiltrate (USMUF) as the effluent. In the present study, we have examined the crosslinking by CCP in artificial casein micelles which were prepared with various salt compositions in order to clarify the role of individual salt constituents. MATERIALS AND METHODSPreparation of artificial casein micelles. Artificial casein micelles were prepared according to the method of Knoop et a1 4 } with minor modifications to give a final casein concentration of 2.5%. Whole casein. which was prepared from bulk milk from the university herd by the acid precipitation method, was dissolved in water by the gradual addition of 1 N sodium hydroxide ensuring that the pH did not exceed 7, and then the pH was adjusted to 6.7. Tke salt solutions used were I M calcium chloride, 1 M magnesiu...

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Section: Discussionmentioning

confidence: 99%

Role of Individual Milk Salt Constituents in Cross-linking by Colloidal Calcium Phosphate in Artificial Casein Micelles

Aoki

Kawahara

Kako

et al. 1987

Agricultural and Biological Chemistry

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“…It is believed that the molar ratio of Ca bound to inorganic phosphate (Ca/ P) is ~1.5-1.6 (Pyne and McGann, 1960;Walstra and Jenness, 1984). It has been reported that CCP in milk has form of 3Ca 3 (PO 4 )•CaH citrate; Ca 9 (PO 4 ) 6 ; CaHPO•2H 2 O, which is acidic, amorphous, and reminiscent of brushite (Holt et al, 2003;Schmidt, 1980).…”

Section: Colloidal Calcium Phosphate (Ccp)mentioning

confidence: 99%

“…During cheese making, most of serum Ca is lost during draining and casein-bound Ca is dissolved when the draining pH is lowered (Lucey and Fox, 1993). Until recently, it was believed that the CCP in milk was completely solubilized during manufacture of cheese and that Ca in cheese was only present in serum phase as most of INSOL Ca in milk is dissolved with pH <5.2 (Choi et al, 2007;Pyne and McGann, 1960). The early attempts to quantify soluble Ca (that fraction that is in serum phase) and INSOL Ca (that fraction that is attached to casein) in cheeses were performed by Lucey and Fox (1993) and Morris et al (1988).…”

Section: Colloidal Calcium Phosphate (Ccp)mentioning

confidence: 99%

The Role of Ca Equilibrium on the Functional Properties of Cheese: A Review

Lee¹,

Lee²

2009

Korean Journal for Food Science of Animal Resources

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The functional properties of cheese, such as texture and melt, are known to be controlled by several important parameters. Recently, the characteristics of Ca in cheeses, especially the form of Ca (insoluble (INSOL) or soluble) and the shift in Ca equilibrium (i.e., from INSOL to soluble Ca), during aging has received a lot of attention. The INSOL form of Ca, which is present as a structural form in casein, plays a critical role in determining the functional properties of cheese during the early period of ripening (~1 mon). It seems that there is always a reduction of INSOL Ca content in cheese during ripening and there are also factors that can affect the shift in Ca equilibrium. These factors may include the composition of cheese milk, cheese manufacturing pH, acid development during aging, adopting curd-washing in various methods, pre-acidification of milk, etc. There have been many studies showing that the rheological and melting properties of cheese during ripening were significantly (p<0.05) affected by the shift in Ca equilibrium. Therefore, for cheese makers, it is now possible to predict/ manage the functional properties of cheese by monitoring and controlling Ca equilibrium in cheese during aging.

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“…Since the colloidal calcium phosphate is mainly responsible for maintaining the integrity of the micelle [30,33], the release of the colloidal minerals into solution during hydrolysis could be considered as an index of casein micelle disruption. With a trypsin concentration of 0.021 U·mL-1 of micellar solution containing 31.6 gTN·kg-1 , we have determined that only 9% (2.8 mmol-L:') of the colloidal calcium and 15.6% (2.1 mmol-Lv') of the colloidal Pi were removed from the micelles after 4 h of hydrolysis.…”

Section: Limited Proteolysis Of the Casein Micellesmentioning

confidence: 99%

“…u s2~, and K) which are present as a colloidal dispersion called casein micelles. They are complexed with colloidal calcium phosphate [37], which has a crucial role in maintaining casein micelle integrity [30,33]. The clearly defined micellar composition and its sizedependence has led to various structural models.…”

Section: Introductionmentioning

confidence: 99%

Preferential sites of tryptic cleavage on the major bovine caseins within the micelle

Gagnaire

Léonil

1998

Lait

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-Caseins, major proteins in bovine milk, are structured in micelles within which the detailed casein organisation remains unclear. We have used limited proteolysis to find the most exposed regions of the caseins within the micelle. Under hydrolysis conditions, only 9% of colloidal calcium and 15.6% of the colloidal inorganic phosphate were removed from the micelle after 4 h. The released peptides during tryptic hydrolysis were separated from the residual micelle by ultracentrifugation. They were subsequently analysed and characterised by reversed-phase HPLC coupled online with electrospray ion source mass spectrometry (ESI-MS). After 4 h of hydrolysis, the p-casein had completely disappeared while about 40% of us,-casein and 37% of x-casein remained undigested. The initial distribution, i.e., 91 % caseins and 9% peptides prior to hydrolysis, was modified after hydrolysis to give 64% peptides remaining within the micelles together with 13% caseins and 22% of the peptides produced were released from the micelles. Among the 61 peptides identified, 34 arose from p-casein, 16 from us1-casein, II from u s2 -casein and none from x-casein. For the latter casein, the failure ta detect peptides was due to its lower concentration in the large micelles cornpared with that of the P and us1-caseins. The peptides derived from p-casein were mainly released from the micelle, while peptides from bath u s1 -and u s2 -caseins were preferentially retained within the residual micelles, suggesting that ail the caseins are accessible ta trypsin but are differentially involved in the micellar framework. Our results suggest that us-caseins play a significant role in the micellar cohesion via salt binding with colloidal calcium phosphate and hydrophobie interaction, with itself and with the other caseins. © Inra/Elsevier, Paris.casein / micelle / Iimited proteolysis / trypsin / reversed-phase chromatography / mass spectrometry / peptide / accessibility Résumé -Sites privilégiés de coupure sur les caséines bovines majeures par trypsinolyse des micelles. Les caséines, constituants majeurs des protéines du lait de vache, sont présentes sous forme de micelles dont l'organisation interne est encore mal connue. Nous avons utilisé la protéolyse limitée pour déterminer les régions des caséines les plus accessibles au sein de la micelle. Dans les conditions utilisées, seuls 9 % du calcium colloïdal et 15,6 % du phosphate inorganique colloïdal sont * Correspondence and reprints: E-mail: jleonil@labtechno.roazhon.inra.fr 472 V. Gagnaire, J. Léonil éliminés de la micelle après 4 h d'hydrolyse. Afin de différencier les peptides qui sont libérés de la micelle de caséine au cours de l'hydrolyse par la trypsine de ceux qui restent situés à l'intérieur, nous avons ultracentrifugé les hydrolysats avant de caractériser les peptides. Leur caractérisation était ensuite réalisée par couplage direct entre la CLHP de phase inverse et la spectrométrie de masse à source d'ionisation electrospray. Après 4 h d'hydrolyse, la caséine~avait complètement dispar...

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The colloidal phosphate of milk: II. Influence of citrate

Cited by 159 publications

References 15 publications

Role of Individual Milk Salt Constituents in Cross-linking by Colloidal Calcium Phosphate in Artificial Casein Micelles

Role of Individual Milk Salt Constituents in Cross-linking by Colloidal Calcium Phosphate in Artificial Casein Micelles

The Role of Ca Equilibrium on the Functional Properties of Cheese: A Review

Preferential sites of tryptic cleavage on the major bovine caseins within the micelle

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