Influence of preparation methods on physicochemical and gelation properties of chickpea protein isolates

Two protein isolates were prepared from defatted chickpea seed flour by applying alkaline extraction followed by isoelectric precipitation or ultrafiltration (TpI and TUF, respectively), while another one (TF) was obtained by a combination of protein extraction at a mildly acidic environment and ultrafiltration processes. The isolates differed in composition, with the TpI and TF containing mainly the chickpea globulins and the albumins, respectively, whereas the TUF isolate consisted of both types of proteins with the globulin fraction dominating over the albumins. The differences in protein composition between the isolates as well as the impact of extraction conditions were reflected in their protein solubility, surface hydrophobicity, sulfhydryl group content, thermal properties and the onset of gelation during heating. On the other hand, the protein isolate gelling behavior depended mainly on the method applied for their preparation rather than the protein composition, with the isolates obtained by ultrafiltration exhibiting lower gelling concentrations and gel networks of higher elasticity at protein contents below 12% (w/v).