Colloidal Stability of Mixed Protein Systems – Milk and Isolated Pea Protein Suspensions

The present study aims to describe the physicochemical characteristics and the colloidal stability of mixed suspensions of pea proteins and skimmed milk. The mixed protein suspensions were prepared by adding pea protein isolate to skimmed milk (3% w/w protein) to generate four mixed samples at 5, 7, 9, and 11% w/w total proteins. Low-heat skimmed milk powder was also added to skimmed milk (3% w/w protein) to prepare four pure milk samples at the same protein concentrations. The samples were analyzed regarding their pH, viscosity, color, amount of sedimentable material, heat and ethanol stabilities. The suspensions containing pea proteins were darker and presented higher pH, viscosity and amount of sedimentable material than the skimmed milk samples. However, the results of colloidal stability revealed a similar tendency for both systems, in which the heat and ethanol stabilities were reduced as function of the protein concentration.