The influence of proteolysis of extruded soy flour (ExSF) with Alcalase conducted under different conditions upon functional properties of hydrolysates was studied. The results were summarised as response surfaces and contour plots. It follows that limited hydrolysis of extruded raw material allows one to obtain products with better functional properties in comparison with non-hydrolysed extrudate, with the exception of water holding capacity (WHC). With progressing hydrolysis, an increasing release of amino nitrogen was accompanied by an increase in solubility (r=0.97, p<0.05) and decreasing WHC (r= -0.85, p<0.05), as well as a decrease of maximum force in back extrusion test (r= -0.96, p<0.05). Changes in foaming and emulsifying properties were more differentiated. As a result of the process optimization, it can be concluded that the best protein hydrolysate, in terms of physicochemical properties, can be obtained from extruded soy flour by conducting the process for 90 min at 60oC, pH 8.3, water added to the raw material 13 g/g protein and with 8 mAU/g protein addition of Alcalase.