Physicochemical characterization of calcium-supplemented skim milk

Abstract

-Addition of CaCl 2 to skim milk, from 0 to 13.5 mmol·kg -1 , leads to significant physicochemical changes in milk salts equilibrium. Indeed, acidification, insolubilizations of calcium, inorganic phosphate and citrate are observed. Calculation of ion equilibria in the resulting milk ultrafiltrates indicates that the observed ion migrations, controlled by solubilities of calciumphosphate and calcium-citrate, do not cause change in ion activity products of dicalcium-phosphate (calculated as CaHPO 4 ·2H 2 O and Ca(HPO 4 ) 0.7 (PO 4 ) 0.2 ). In the same way, the acidification of calcium-supplemented milks in the range of pH 6.7-3.5 shows a solubilization of calciumphosphate similar to non-enriched milk. So whatever the added calcium concentration, the behaviour of colloidal calcium-phosphate seems to be unchanged. However, at room temperature, addition of calcium to milk originates a decrease in soluble casein concentration and tightly bound water of ultracentrifuged pellets. The consequences are (i) an increase in milk protein hydrophobicity; (ii) a decrease in zeta potential of casein micelles, without modification of their hydrodynamic diameter; and (iii) an increase in milk lightness and turbidity. Furthermore, calcium supplementation of milk seems to lead to a proteinic reorganization of micellar casein, responsible for an increase in micellar density. Milk / calcium / physicochemical characterization / calcium phosphate / acidification / supplementationRésumé -Caractérisation physicochimique d'un lait écrémé enrichi en calcium. L'addition de CaCl 2 à du lait écrémé, pour des concentrations allant de 0 à 13,5 mmol·kg -1 , induit d'importants changements physicochimiques du lait. En effet, une acidification, une insolubilisation du calcium, du phosphate inorganique et du citrate sont observées. Le calcul des équilibres ioniques dans les ultrafiltrats des différents laits montre que les flux ioniques observés, contrôlés principalement par les solubilités du phosphate et du citrate de calcium, ne modifient pas les produits d'activité ionique du phosphate dicalcique (calculés pour CaHPO 4 ,2H 2 O et Ca(HPO 4 ) 0,7 (PO 4 ) 0,2 ). De la même manière, l'acidification de ces laits supplémentés en calcium entre pH 6,7 et 3,5 montre une solubilisation du phosphate de calcium similaire à celle d'un lait non enrichi. Quelle que soit la concentration en calcium ajouté, le comportement du phosphate de calcium colloïdal semble donc inchangé. Par ailleurs, l'addition de calcium à du lait écrémé est responsable, à température ambiante, d'une diminution de la concentration en caséines ultracentrifugeables et de l'eau

Seasonal variation, method of determination of bovine milk stability, and its relation with physical, chemical, and sanitary characteristics of raw milk

“…Horne and Muir (1990), Chavez et al (2004), and Lewis (2011) reported that results in the ethanol test and CTT were adversely affected by ionic calcium concentration. The output of calcium phosphate from the micellar structure leads to the exposition of the hydrophobic portion of the caseins, enhancing the propensity for aggregation (Philippe et al 2003).…”

The minerals of milk

“…Theoretically, the modifications of salt balance are controlled by the solubilities of cation phosphate and cation citrate salts in the diffusible fraction [33]. In the literature, the modifications of salt balance of milk induced by calcium addition are the most described [34]. Thus, after the addition of 10 mM calcium chloride to milk, about 80% of this ion was associated to casein micelles.…”

Rheological behavior of concentrated skim milk dispersions as affected by physicochemical conditions: change in pH and CaCl2 addition

“…Both physicochemical changes lead to smaller contribution of electrostatic and steric repulsion and, hence, dispersions exhibit more fluid characteristics. Also, in the case of samples S3, pH value resulted lower (pH = 6.0) than the natural pH of milk as a consequence of the concentration process and the salt addition (Bienvenue et al 2003;Philippe et al 2003). Bienvenue et al (2003) reported that concentration of milk causes an increase in ionic strength and a decrease in pH.…”

“…Bienvenue et al (2003) reported that concentration of milk causes an increase in ionic strength and a decrease in pH. Philippe et al (2003) stated that a decrease in pH value after calcium addition to milk is related (i) to the formation of calcium phosphate and calcium-citrate; (ii) to exchanges between added calcium and micellar H + ; and (iii) to the acidity of the added calcium solution. Full lines in Fig.…”

“…Moduli G′ and G″ of this dispersion did not scale as f 2 and f 1 , respectively, indicating that the dispersion does not behave as a classical viscoelastic fluid at low frequencies (Macosko 1994) but it is in a transition regime from liquid to gel (Bouchoux et al 2009). As pH decreases, colloidal calcium phosphate (CCP) is solubilized (Philippe et al 2003). Therefore, in skim milk concentrates, ionic strength increases due to both concentration process and CCP solubilization.…”