Kinetics of aggregation of αs1 -casein/ca2+ mixtures: charge and temperature effects

Dalgleish, Douglas G.; Paterson, Eva; Horne, David S.

doi:10.1016/0301-4622(81)85004-1

Cited by 25 publications

(9 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…3) but is strengthened when pH is increased and that strength passes through a maximum when the ionic strength of the buffer is inreased. Thus the calcium ion effect would result from specific ion-binding reducing the net negative charge, decreasing inter-hair repulsion and making them more susceptible to collapse, similar effects to those observed in calcium-induced aggregation of the individual caseins [21,22]. Thus the calcium ion effect would result from specific ion-binding reducing the net negative charge, decreasing inter-hair repulsion and making them more susceptible to collapse, similar effects to those observed in calcium-induced aggregation of the individual caseins [21,22].…”

Section: Discussionmentioning

confidence: 86%

The effect of environmental conditions on the steric stabilization of casein micelles

Horne

Davidson

1986

Colloid & Polymer Sci

View full text Add to dashboard Cite

In an attempt to characterize the steric stabilizing sheath around the casein micelles of bovine milk, photon correlation spectroscopy techniques have been used to measure the micellar radius on exposure to ethanolic buffers of varying pH, ionic strength and calcium concentration. It is shown that on exposure to alcohol, the stabilizing protein sheath undergoes dimensional collapse and that immediately prior to aggregation, a minimum or core radius is reached, characteristic of the diluting buffer conditions. Defining barrier thickness as the difference between the micellar radius in alcoholfree buffer and this minimum radius, the same linear relationship is observed between barrier thickness and the critical ethanol concentration required to reach the core radius and induce subsequent aggregation, whether those variations in barrier thickness were achieved by altering the pH, ionic strength or calcium level of the buffer. Considering the initial rate of response to added ethanol as a measure of barrier strength, it is observed that thicker barriers are weaker whereas thinner barriers are more resistant to collapse and hence intrinsically stronger. This paradox is qualitatively resolved by considering the stabilizing sheath to possess some of the characteristics of a weak or soft gel, whose rigidity or extent of cross-linking is influenced by the variations in buffer conditions.

show abstract

Section: Discussionmentioning

confidence: 86%

The effect of environmental conditions on the steric stabilization of casein micelles

Horne

Davidson

1986

Colloid & Polymer Sci

View full text Add to dashboard Cite

show abstract

“…It is well known that α s1 -, α s2 -, β-casein can bind Ca 2+ because they contain phosphoester groups [43][44][45][46], and pure solutions of these caseins precipitate when Ca 2+ is added. We have found that caseinate quickly precipitates completely in the presence of Ca 2+ , while in the absence of Ca 2+ only a small fraction (20%) of caseinate precipitates, even after extensive heating at 80 • C. Strikingly, if both polyphosphate and CaCl 2 are added to a solution of caseinate then, under certain conditions, gels are formed that are similar to those formed by submicelle solutions.…”

Section: Aggregation Mechanismmentioning

confidence: 99%

Aggregation and gelation of micellar casein particles

Panouillé

Durand

Nicolai

et al. 2005

Journal of Colloid and Interface Science

View full text Add to dashboard Cite

“…Hayakawa & Nakai (1985) proposed that proteins do not coagulate at the isoelectric pH when hydrophobic forces are too weak to cause coagulation. This hypothesis was also given by Parker & Dalgleish (1981) to explain why /?-casein does not coagulate in CaCl 2 solution at low temperature (4 °C, pH 7-0). However, the repulsive forces that counterbalance the weak hydrophobic forces between proteins were not mentioned.…”

mentioning

confidence: 62%

Effects of cations and anions on the rate of the acidic coagulation of casein micelles: the possible roles of different forces

Bringe

Kinsella

1991

Journal of Dairy Research

View full text Add to dashboard Cite

Raw skim milk was diluted 1000-fold using distilled water or various salt solutions as specified. Smooth, hyperbolic profiles of coagulation rate v. pH for casein were calculated from recordings of turbidity (400 nm) with time. The effects of pH, cation type, anion type and cleavage of/c-casein by chymosin (EC 3.4.23.4) were determined. The maximum of pH-coagulation rate profiles decreased by 63, 85 and 94 % when the skim milk diluent was changed from water to salt solutions of NaCl (100 mM), CaCl 2 (50 mM) or MgCl 2 (50 mM). The maximum of the pH-coagulation rate profile was 15 times greater when the Ca salt was changed from CaCl 2 to Ca(SCN) 2 (50 mM). The highest pH at which casein coagulation occurred increased from 4 -45 to > 6*0 when Cu 2+ (1 mM) was included with casein micelles dispersed in CaCl 2 solution (50 mM). The addition of chymosin to casein micelles suspended in CaCl 2 solution (70 mM) eliminated the inhibition of casein coagulation by Ca 2+ at pH 4 -5. It is proposed that ions such as Mg 2+ , Ca 2+ , and Na + , which generally associate with casein phosphate and carboxylate groups, increased the H + concentration required to initiate the coagulation of casein, because H + must displace bound Ca 2+ , Mg 2+ or Na + to reduce repulsive hydration forces between casein micelles, allowing attractive hydration forces (e.g. hydrophobic phenomena) to cause casein coagulation. Furthermore, it is proposed that ions such as Cl~, Br~, N0 3~ and SCN~ bind to lysine, arginine and histidine groups and thereby decrease repulsive hydration forces between cationic casein micelles.

show abstract

Kinetics of aggregation of αs1 -casein/ca2+ mixtures: charge and temperature effects

Cited by 25 publications

References 23 publications

The effect of environmental conditions on the steric stabilization of casein micelles

The effect of environmental conditions on the steric stabilization of casein micelles

Aggregation and gelation of micellar casein particles

Effects of cations and anions on the rate of the acidic coagulation of casein micelles: the possible roles of different forces

Contact Info

Product

Resources

About