Effects of Emulsifying Salts on the Turbidity and Calcium-Phosphate–Protein Interactions in Casein Micelles

Abstract

Influence of emulsifying salts (ES) on some physical properties of casein micelles was investigated. A reconstituted milk protein concentrate (MPC) solution (5% wt/wt) was used as the protein source and the effects of ES [0 to 2.0% (wt/wt)] were estimated by measuring turbidity, acid-base titration curves and amount of casein-bound Ca and inorganic P (P(i)). Various ES, trisodium citrate (TSC), or sodium phosphates (ortho-, pyro-, or hexameta-) were added to MPC solution, and all samples were adjusted to pH 5.8. Acid-base buffering curves were used to observe changes in the amount and type of insoluble Ca phosphates. An increase in the concentration of TSC added to MPC solution decreased turbidity, buffering at pH approximately 5 (contributed by colloidal Ca phosphate), and amount of casein-bound Ca and P(i). Addition of up to 0.7% disodium orthophosphate (DSP) did not significantly influence turbidity, buffering curves, or amount of casein-bound Ca and P(i). When higher concentrations (i.e., > or =1.0%) of DSP were added, there was a slow decrease in turbidity. With increasing concentration of added tetrasodium pyrophosphate (TSPP), turbidity and buffering at pH approximately 5 decreased, and amount of casein-bound Ca and P(i) increased. When small concentrations (i.e., 0.1%) of sodium hexameta-phosphate were added, effects were similar to those when TSPP were added but when higher concentrations (i.e., > or =0.5%) were added, the buffering peak shifted to a higher pH value, and amount of casein-bound Ca and P(i) decreased. These results suggested that each type of ES influenced casein micelles by different mechanisms.

Calcium-binding capacity of organic and inorganic ortho- and polyphosphates

“…Also, SHMP (Fig. 1b) micelles by binding calcium ions [14][15][16][17]. SHMP is a strong chelator and its binding to polyvalent cations is equal for calcium, magnesium, strontium, and barium [32].…”

“…The extent of interaction of polyphosphates is, in general, dependent on the chain length of the polyphosphate [32]. Na 2 HPO 4 binds less strongly with calcium than SHMP, even when extremely high Na 2 HPO 4 concentrations are used [14]. Nucleotides, such as disodium uridine monophosphate (Na 2 UMP) (Fig.…”

“…Addition of calcium and phosphate causes interactions with casein micelles, CCP, and soluble calcium phosphate. As a result, insoluble or soluble calcium phosphate complexes will be formed [1,4,14,20,21,29]. Many calciumbinding agents are used in the dairy industry, for example, citrate, polyphosphates, or pyrophosphates, and they are named chelators [4,18].…”

The effect of individual phosphate emulsifying salts and their selected binary mixtures on hardness of processed cheese spreads

“…Low values in samples with trisodium citrate could be explained with their low affinity to calcium ions and low ability to protein hydratation. It is not capable to crosslink protein matrix and it could reduce hardness values of processed cheese (Mizuno & Lucey, 2005;.…”

Influence of low calcium and low pH on melting characteristics of model Raclette cheese

“…The storage modulus G′ is a measure of the energy stored and released per oscillation cycle, which can be used as the index of rigidity or elastic characteristics (and when it decreases, it indicates softening of the cheese). LT indicates the ratio of viscous to elastic properties and is related to the relaxation of bonds in the matrix [26,34]. LT max indicates the point of highest bond mobility and is often used as a reliable index of meltability or flowability [37].…”