High pressure-induced solubilisation of micellar calcium phosphate from cross-linked casein micelles

The study presented in this communication used in situ turbidity measurements to estimate the extent of solubilisation of micellar calcium phosphate (MCP) on high pressure (HP) treatment. For this purpose, a suspension of casein micelles cross-linked by transglutaminase was used. The protein network in cross-linked casein micelles is stable against disruption so any HP-induced reduction in turbidity has to derive from solubilisation of MCP. Comparison of model calculations with experimental data indicate that in a 25 g L^-1 casein micelle suspension (comparable to skim milk) solubilisation of MCP increases in near-linear fashion with pressure; at 100, 200 or 300 MPa, ∼25, 50 or 75% of MCP was solubilised. Extrapolation indicated that in normal milk, all MCP would be solubilised at ∼400 MPa. The estimates correlate excellently with previous observations on HP-induced disruption of casein micelles.