Heat stability of reconstituted casein micelle dispersions: changes induced by salt addition

The aim of the present work was to study the heat stability of reconstituted casein micelle dispersions (RCMD) after addition of various salt solution: NaCl, CaCl2, MgCl2, sodium citrate and sodium phosphate. Casein micelle stability to heat treatments (95 degrees C - 10, 20 and 30 min) was evaluated. Modifications of the pH, of the casein micelle pellet water content and of the mineral and casein distribution between aqueous and micellar phase were measured. NaCl addition decreased the RCMD pH, increased the amount of diffusible calcium and decreased the amount of supernatant casein. CaCl2 and MgCl2 addition decreased the RCMD pH and the amount of supernatant casein. Sodium citrate addition, with a solution at pH 7.4, increased the RCMD pH, drastically increased the amount of diffusible calcium, phosphorus and of supernatant casein. It caused the casein micelle's destructuration. Sodium phosphate addition, with a solution at pH 7.4, did not modify the RCMD pH and increased the amount of supernatant casein. Acidification, beyond a pH value of 7.0, induced heat aggregation. Calcium and magnesium chloride addition was detrimental to casein micelle heat stability. NaCl, sodium citrate and sodium phosphate addition enhanced reconstituted casein micelle heat stability. The determinant role of the aqueous phase on reconstituted casein micelle physico-chemical properties was emphasized by this study. (C) Inra/Elsevier, Paris.