Pomegranate seed protein isolate obtained from isoelectric precipitation: functional and physicochemical characteristics

The aim of the present study was to evaluate the functional and physicochemical characteristics of pomegranate seed protein isolate (PSPI) obtained by an isoelectric precipitation process. The extracted isolate had a desirable nutritional value as the contents of its essential amino acids (except for valine and isoleucine) exceeded those recommended by FAO/WHO for adults. The molecular weights of the protein fractions of PSPI were found to be within 15-60 kDa range. According to thermal analysis data, PSPI could be denatured at 90 °C. Surface hydrophobicity of PSPI was determined at 774 level. PSPI showed high solubility both in alkaline and acidic media with the highest solubility at pH 12 (96.6%). Solubility of PSPI at pH 7.0 was at 39.5%. Furthermore, PSPI had good oil- and water-holding capacity (3.7 and 4.3 g g-1, respectively), emulsifying and foaming properties, and in-vitro digestibility. The lowest emulsifying activity index (14.1 m2/g) and emulsion stability index (8.18%) were obtained at the isoelectric pH. Overall, PSPI as a novel protein source shows a potential for future industrial applications.