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Molecular and thermal characterization of white lupin (Lupinus albus) protein isolates


In this work differential scanning calorimetry (DSC) and SDS-PAGE techniques were used to study protein isolates from white lupine seeds flour (Lupinus albus). The white lupine seeds flour was obtained with a protein content of 49.88 ± 0.08%. Samples solubility curves were obtained by pH adjustment in the interval of 1 to 12, both in the presence and absence of salts (NaCl, 0.3, 0.5 mol L-1 and in Na2SO3 0.25%, w/v), followed by protein isoelectric precipitation. Protein isolates (PIs) obtained in the pH range of 7 to 10, in the presence of NaCl 0.3 mol L-1, showed protein content (PC) in the range of 83.7 to 92.6, while for pH 10, in the presence of NaCl 0.5 mol L-1, followed by dialysis, a protein content of 96.6 ± 1.6 %, was obtained. These PIs and the white lupine flour were submitted to SDS-PAGE and thermal analysis. The protein migration patterns in SDS-PAGE from all white lupine samples tested were identical, presented 8 electrophoretic bands with molecular masses ranging from ~14 to 71 kDa. No differences were observed between the protein migration patterns of white lupine flour and protein isolate samples, independently of the isolation method used. This suggests that the experimental conditions used to obtain the protein isolates did not alter the white lupine native protein profile. However, the DSC curves for PIs extracted at pH 7 showed that deltaH values were ~15 % superior to those found for PIs extracted at pH 10 and in the absence of salts. This suggests the obtaining of a protein isolate of higher stability in neutral conditions and the maintenance of the original conformation. The Tpeak of PIs obtained at pH 7 (NaCl 0.3 mol L-1) and alkaline conditions (pH 10 to 11, in the absence of NaCl salt) did not significantly changed maintaining the values approximately at 70ºC. For PIs extracted in pH values from 8 to 9, in the presence of NaCl 0.3 mol L-1, Tpeak was displaced towards smaller temperatures (deltaTpeak ~ 5 ºC). This temperature difference could be due to differences in the protein structure.


DSC; Protein isolate; SDS-PAGE

Tipo de Apresentação
Comunicação oral
Tipo de Revisão
Âmbito Geográfico

Fontanari, G; Martins, J; Kobelnik, M; Pastre, I; Fertonani, F; Arêas, J; Batistuti, J; (2008). Molecular and thermal characterization of white lupin (Lupinus albus) protein isolates. 14th ICTAC – International Congress on Thermal Analysis and Calorimetry & VI CBRATEC – Brazilian Congress on Thermal analysis and Calorimetry. São Pedro, SP (Brasil). Publicado em CD (3 pp, sem numeração).