New methods of protein concentration providing the regulation of its functional properties based on the phenomena of limited thermodynamic compatibility and complexation of proteins and polysaccharides (PS) are considered. Formation of two-phase systems for skimmed milk, clover biomass sap, and PS (pectin, arabic gum, arabinogalactan) of different kinds is studied. Establishing the phase equilibrium in all cases is accompanied by concentration of proteins and dilution of PS solution. The PS phase is as a rule, a continuous medium, and the concentrated protein phase is a dispersed phase. The first stage of the process consists in establishing the phase equilibrium. The second stage consists in phase separation. The third stage is a recovery of PS from the PS phase in the form of protein, PS complex, and recycling of PS.

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 QS 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 7;) of the water-skimmed milk proteins-polysaccharide system was observed to take place at 10 'C. a-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.

Earlier, with particular reference to skimmed milk, it has been shown that protein solutions can be concentrated by the membraneless osmosis. The practical significance of this method is determined by the possibility of the regeneration of the polysaccharide from its diluted so1ut;ons (from the polysaccharide phase) and its repeated use for protein concentration. This work deals with the possibility of pectin isolation from the polysaccharide phase resulting from the phase separation of the water-skimmed milk proteins-pectin system and its further use for milk protein concentration. The pectin was precipitated as a part of the insoluble complexes with milk proteins at pH values below their IEP. The complexes were destroyed at pH values being increased to 6.5-6.7 and the pectin obtained was used again in the process of the membraneless osmosis. In case of a single-cycle regeneration and repeated use of pectin the total loss of protein did not exceed 2.6:;and that of pectin 30 %. The amount of water removed with unit weight of pectin during a single-cycle pectin regeneration was 1.7 times higher than th&t which took place during concentratio? without subsequent regeneration. The additional energy expenditures due to the single-cycle regeneration and the repeated use of pectin did not exceed 15 % of the energy spent in all the cycles of protein concentration.