Effect of calcium on the hydration of casein. I. Water vapour sorption and fine structure of calcium caseinates compared with sodium caseinates in the pH range 4·6–8·0

Abstract

0 3Effect of calcium on the hydration of casein. I. Water vapour sorption and fine structure of calcium caseinates compared with sodium caseinates in the pH range 4-6-80 SUMMARY. Hydration of Ca and Na caseinates which were prepared from whole casein at different pH levels (range 4-7-8-0) was determined by means of water vapour sorption measurements in the water activity (a w ) range O58-O95. Water uptake of Ca caseinates was systematically lower than that of Na caseinates prepared at equal pH, the differences increasing with increasing pH and a w . Plots of the water content v. the amount of added hydroxide at constant a w revealed a linear relationship between water uptake and cation content, suggesting that the increase in water uptake is mainly determined by the amount and type of cations associated with the caseins.In the a w range tested, Ca 2+ adsorbed about 2-7 and Na + 3-18 mol water/mol of cation. This implies that replacement of one mol of casein-bound Na + by Ca 2+ is accompanied by a displacement of 1-11 mol water at a w 0-58-0-95. The loss of water is a consequence of conformational changes induced by the chelating and cross-linking effects of Ca 2+ , which also lead to micelle formation.

Mobility and Activity of Water in Casein Model Systems as Determined by 2H NMR and Sorption Isotherms

“…For example, the sodium caseinate sorbed approximately 0.0075g water/g solid more water than the micellar casein at a,,, 0.59 but sorbed approximately 0.14Og water/g solid more water at a,., 0.80. These results are similar to those reported here and those reported by Ruegg and Moor (1984) for hydration of sodium caseinate.…”

Effects of reducing milk pH to 6.2 by CO2 injection or by addition of lactic acid on the biochemical and functional properties of commercial low-moisture part-skim mozzarella

“…The lower total Ca and higher moisture content of DA2 cheese concurs with the results of previous studies, i.e., higher moisture content in reduced-fat Cheddar and Mozzarella cheeses made from milk pre-acidified to pH 6.2 with lactic acid in the absence of pertinent process interventions (Banks, 1988;Banks et al, 1987;Guinee et al, 2002), and reduced total Ca content with pH reduction to 6.2 prior to coagulant addition (Banville et al, 2013;Guinee et al, 2002;Joshi et al, 2004). These trends are consistent with the higher solubilization of CCP in cheese curd as the pH of milk is reduced prior to gelation (van Hooydonk et al, 1986), and the inverse relationship between casein hydration and concentration of casein-bound Ca (Rüegg & Moor, 1984;Sood, Gaind & Dewan, 1979). Hence, the higher total Ca and lower moisture of DA1 compared to DA2 cheese is attributed to the increase in pH (~ 0.1 unit) during the starter incubation and gelation stages of DA1 manufacture (Fig.…”

The role of dairy ingredients in processed cheese products

“…Gouda, Cheddar) occurs as paracasein aggregates, rendered insoluble by inter-protein linkages mediated by calcium (attached to acidic amino acid residues such as glutamate and aspartate), colloidal calcium-phosphate (attached to serine phosphate groups), and hydrophobic interactions between uncharged amino acid residues. The depressing effect of calcium phosphate on paracasein hydration has been corroborated by studies in model (dilute) casein systems Green, 1982;Ruegg and Moor, 1984;Snoeren et al, 1984) and cheese (Guinee et al, 2000a). The calcium content of natural cheeses exhibits marked inter-(e.g.…”