Stable casein micelle dispersions at pH 4.5 enabled by propylene glycol alginate following a pH-cycle treatment

Polysaccharides may form stable complexes with caseins to prevent precipitation near the isoelectric point of pH 4.6. In this study, dispersions of 1% w/v micellar caseins and propylene glycol alginate (PGA) were treated with a pH-cycle treatment from neutral to pH 11.30, to dissociate casein micelles, and then to pH 4.5 to re-associate caseins to form complexes with PGA. An increase in PGA concentration overall resulted in the reduced dispersion turbidity. The dispersion with equal masses of casein and PGA following the pH-cycle treatment had the lowest turbidity (260 NTU) and was absent of both precipitation and gelation during 30-day storage at 21 °C, contrasting with unstable and turbid (>4000 NTU) dispersions directly acidified to pH 4.5. The dispersion turbidity was determined by both the size and mass density of particles, and both covalent and non-covalent (mainly electrostatic and hydrophobic) interactions contributed to the complex formation and dispersion stability at pH 4.5.