Functional properties of pumpkin (Cucurbita pepo) seed protein isolate and hydrolysate

Pumpkin seed protein isolate (PSPI) was enzymatically hydrolysed by pepsin to obtain pumpkin seed protein hydrolysate, PSPH. Investigation on solubility, interfacial and emulsifying properties of both PSPI and PSPH was conducted under different conditions of pH (3–8) and ionic strength (0–1 mol/dm 3 NaCl). PSPI had the lowest solubility, i.e. isoelectric point (pI), at pH 5. PSPH had higher solubility than PSPI over whole range of pH and ionic strengths tested. Decrease in surface and interfacial tension evidenced that both proteins adsorb at air/protein solution and oil/protein solution interface. 20 % oil in water emulsions stabilized by 1 g/100cm 3 PSPI or PSPH solution were prepared at pH 3, 5 and 8 and ionic strength of 0 and 0.5 mol/dm 3 NaCl. PSPH stabilized emulsions from coalescence at all pH and ionic strengths tested. PSPI was able to stabilize emulsions at pH 3 and 0 mol/dm 3 NaCl and at pH 8, regardless of ionic strength while emulsions at pH 5 and both 0 and 0.5 mol/dm 3 NaCl and at pH 3 when ionic strength was increased separated to oil and serum layer immediately after preparation. All emulsions were susceptible to creaming instability.