Formation of co-assembled structures by spontaneous association of oppositely charged globular proteins has increasing interest for the design of new supra-molecular structures. These supra-molecular structures present diverse properties and have been associated with innovative applications such as the encapsulation of bioactives. Our work reports on the impact of subtle change of protein charge on coacervation and subsequent liquid-liquid phase separation. The present communication focuses on lactoferrin (LF) and the two β-lactoglobulin (β-LG) isoforms.Upon mixing, LF and β-LG form microspheres throughout coacervation under narrow pH range (5.4-6.0) and well defined protein molar ratio. At the optimal pH, an excess of β-LG over LF is required for coacervation, LF being the limiting partner under tested concentration ranges. The β-LG/LF molar ratio recovered in the formed coacervates varied from 4 to 8 depending on the total protein concentration. A mechanism was proposed to explain such molar ratio increase. Remarkably, LF showed a selective coacervation with isoform A of β-LG as judged by a larger coacervation domain (Figure 01) and a high yield of LF recovered in the coacervate phase once mixed with β-LG A i.e. 80% against a maximum of 42% with β-LG B.The interaction parameters between LF and β-LG isoforms, as assessed by isothermal titration calorimetry (ITC), were not found to be significantly different. Both β-LG isoforms exhibited complex exothermic binding isotherms with both enthalpic and entropic contributions.Investigations are presently conducted to understand the origin of the specific association of β -LG isoforms with LF, in particular the role of amino-acid substitutions from Asp and Val (β-LG A) to Gly and Ala (β-LG B)