Concentration of proteins as a result of the phase separation of water‐protein‐polysaccharide systems Part 2. Concentration of milk proteins

Abstract

Abstract The process of concentration of skimmed milk proteins as a result of the phase separation of the waterskimmed milk proteins‐polysaccharide systems has been studied. The two‐phase systems were obtained by mixing and laying‐up skimmed milk and polysaccharide solutions. Used as polysaccharides were pectin, gum arabic and arabinogalactan. The establishment of the phase equilibrium in all the systems under study involves the concentration of the skimmed milk proteins and dilution of the polysaccharide solution. For the water‐skimmed milk proteins‐pectin system one can observe a transition of the lactose and calcium ions from the milk to the pectin solution. Depending on the concentration conditions, the concentration of the skimmed milk proteins in the protein phase increases by a factor of 5‐12 as compared with that in milk. The dispersed phases of the water‐skimmed milk proteins‐gum arabic and water‐skimmed milk proteinsarabinogalactan systems are represented by gel‐like particles with skimmed milk concentrations of 30 and 45 wt %, respectively. A value of 30 wt % for the skimmed milk concentration seems to correspond to the critical concentration of the lyotropic gelation of the skimmed milk proteins. The largest involvement of the skimmed milk proteins in the protein phase (91%) of the water‐skimmed milk proteins‐polysaccharide system was observed to take place at 10°C. α‐Lactalbumin is the major protein component of the polysaccharide phase. This concentration process can be defined as a membraneless osmosis. The rate of the process was studied and the time of the establishment of equilibrium in the two‐phase systems obtained by mixing and laying‐up the solutions was estimated. The greater effectiveness of the membraneless osmosis was shown to be mainly ensured by a fairly large size of the interphase surface of the systems under study.