The effects of various processing conditions on a protein isolate from Lupinus angustifolius

Lupin protein is a promising ingredient in functional foods because of its purported hypocholesterolaemic and hypotensive activities. In this study a lupin protein isolate from Lupinus angustifolius was thermally and mechanically treated and the effects on its protein profile were determined. As a preliminary step, the main protein components of L. angustifolius were identified, using the canonical proteomic approach, including 2D-separation and mass spectrometry and, whenever necessary, also de novo peptide sequencing. Most of the main spots were assigned to the major lupin storage proteins: alpha-conglutin, beta-conglutin, gamma-conglutin, and delta-conglutin. The protein degradation induced by the different treatments was studied via differential scanning calorimetry (DSC), 2D-electrophoresis, and mass spectrometry, in order to get the fingerprint of the intact peptides after processing. The results indicate that, even after harsh industrial processing, alpha-, beta- and delta-conglutin are still able to release stable peptides, although they are completely or partially degraded, as shown by the 2D protein profiles and the DSC graphs. (C) 2009 Elsevier Ltd. All rights reserved.