Stability of casein micelle subjected to reversible CO2 acidification: impact of holding time and chilled storage.

摘要

Casein micelle stability and reactivity were assessed on milk subjected to reversible acidification by carbonation. Pressurised CO2 was injected at 4 degrees C, leading to controlled acidification from 6.63+or-0.02 to a target pH (5.5 or 5.2). After holding the pressurised milk under these conditions for 15 or 60 min, the pressure was released and the milk pH returned to its initial value under stirring and vacuum degassing. Upon CO2 treatment, calcium and protein partition, zeta potential and size of casein micelles were restored directly after neutralization. The rheological properties of the gel obtained by acid coagulation of CO2-treated milk did not change as a result of carbonation. Micelle hydration increased after neutralization and during storage. Milk buffering capacity in the pH range of 4.5-5.5 decreased after neutralization of milk acidified by carbonation, but increased during chilled storage of this milk. Holding time of carbonated milk at low pH was found to have no impact on the physicochemical characteristics of casein micelles and the rheological properties of the gel obtained by acid coagulation of this milk..