Effect of protein composition and homogenisation on the stability of acidified milk drinks

Acidified milk drinks are commonly stabilised by the presence of high methoxyl pectin. Pectin is electrosorbed to the protein particles and prevents their flocculation by steric hindrance. Furthermore, a weak mixed gel of casein and pectin reduces sedimentation. In this study acidified milk drinks were produced in a pilot plant with homogenisation pressures between 20 and 80MPa. The target was to assess the influence of the protein particle size distribution on the stability of the acidified milks. Additionally, the process steps for the production of acidified milks were varied to examine the role of whey proteins in the stabilisation. Particle size was decreased by homogenisation. A destabilising influence of the presence of bigger particles like protein clusters was found. A preheating step that denatured the whey proteins in skim milk and bound them onto the casein micelles before acidification improved stability. In general, the protein concentration, the ionic composition and strength, the particle size and the process history of the reaction mixture affected the stability of the acidified milk.