Improvement of emulsifying properties of lupin proteins by high pressure induced aggregation

Aggregation of lupin (Lupinus albus) proteins induced by high-pressure treatment has been investigated in relation with their interfacial and emulsifying properties. Proteins were extracted from lupin meal in Tris-HCl buffer at pH 7.0 and pressurised at 15 g/l prior to emulsion preparation. High-pressure conditions were 200, 400 and 600 MPa for 10 min at 10 degreesC. Oil-in-water emulsions (30% oil fraction) were prepared with valve homogeniser at 20 MPa. Interfacial and emulsifying properties (oil droplets size, emulsion stability, interfacial protein concentration and rheological behaviour) were evaluated. Size chromatography exclusion studies on lupin proteins indicated that 11S (alpha-conglutin) fraction was extensively aggregated after a pressure treatment higher than 400 MPa. A decrease of protein solubility was concurrently revealed, indicating a partial dissociation of monomers. High pressure (400 MPa) treated lupin proteins gave emulsions with lower values of droplet size, an increase of interfacial protein concentration (mg/m(2)) and a decrease of creaming and flocculation index as compared to control proteins. Therefore the sodium dodecyl sulfate (SDS)-electrophoresis patterns of adsorbed and non-adsorbed proteins in the interfacial film showed that proteins could be selectively adsorbed according to pressure treatment. This study has shown the improvement of emulsifying properties of lupin proteins from high-pressure treatment at 400 MPa. (C) 2003 Elsevier Science Ltd. All rights reserved.