Mechanical and thermal processing effects on protein integrity and peptide fingerprint of pea protein isolate

Pea protein is considered to be an emerging alternative for the formulation of numerous food products, including functional foods, because of its purported hypolipidemic, anti-hypertensive and hypoglycaemic activities. The present investigation was designed to evaluate the effects of thermal and mechanical treatments on an industrial pea protein isolate (Pisane®) from Pisum sativum L. As a preliminary step, the main protein components of P. sativum seed were identified, using the canonical proteomic approach, including 2D-separation and mass spectrometry. Most of the main spots were assigned to the major pea storage proteins: legumin, vicilin and convicilin. Differential scanning calorimetry and proteomic techniques were used to investigate the effects of processing on the protein profile and to assess the availability of stable peptides. After prolonged treatments, no proteins were present in their native forms and the protein solubility was greatly decreased; however, some intense spots were still present on 2D-gels. The spot identity was confirmed by HPLC-Chip-MS/MS, showing that the vicilin 30 kDa fragment and legumin acidic subunits were resistant and some specific peptides remained intact. DSC thermograms showed that strong treatments decreased the denaturation enthalpy. The mechanical treatments, instead, did not modify (in a relevant way) either the protein profile or DSC thermograms.