The effects of various processing conditions on a protein isolate from Lupinus angustifolius investigated by different approaches

Food industry has an increasing interest for food ingredients with improved technological and nutritional properties: plant proteins, for example, may replace milk and egg proteins in numerous applications. Lupin kernel may provide innovative ingredients, since it has valuable nutritional characteristics, such as useful contents of vitamins and macro/microelements and a protein endowed with satisfactory essential amino acid contents. For its techno-functional properties, lupin can be used as emulsifying and coloring agent, for taste enhancing, water retention, texture improvement, and shell-life extension. In addition, recent literature has reported some useful health benefits related to lupin consumption, such as hypocholesterolemic 1-5, anti-atherogenic 6, and hypotensive 3, 7 activities. With the objecting of investigating the consequences of processing on protein integrity, a lupin protein isolate from Lupinus angustifolius was treated thermally and mechanically and the effects on the protein profile were determined. As a preliminary step, a proteome analysis was performed in order to identify the main protein components of L. angustifolius. A combination of two experimental approaches was used: a) the canonical proteomic approach including 2D-separation and mass spectrometry analysis of tryptic peptides; b) the “de novo peptide sequencing". Fifty-five out of 57 main spots were found to belong to the major seed protein families: α-conglutin (legumin), β-conglutin (vicilin), γ-conglutin, and -conglutin. The protein degradation was studied via differential scanning calorimetry, 2D-electrophoresis, and mass spectrometry, which enabled the fingerprint of the available peptides after processing. The results indicate that, even after prolonged industrial processing conditions, -, - and -conglutin are still able to release intact peptides, although they are completely or partially dissociated as shown by the 2D protein profiles and the DSC graphs. References 1. Sirtori, C. R.; et al. J Nutr 2004, 134 (1), 18-23. 2. Martins, J. M.; et al. J Lipid Res 2005, 46 (7), 1539-47. 3. Naruszewicz, M.; et al. Circulation 2006, 114 (18), 874-874. 4. Bettzieche, A.; et al. Br J Nutr 2007, 1-11. 5. Spielmann, J.; et al. Ann Nutr Metab 2007, 51 (4), 387-92. 6. Marchesi, M.; et al. Br J Nutr 2008, 1-4. 7. Pilvi, T. K.; et al. J Physiol Pharmacol 2006, 57 (2), 167-76.