Comparative study of functional properties of protein isolates obtained from three Lupinus species

Abstract

Protein isolates from Lupinus albus, Lupinus splendens Rose and Lupinus spp., seeds,were obtained by isoelectric precipitation of its proteins at pH 4.4, 4.8 and 4.1, respectively. The recovered protein was greater from L. albus (93  0.77%), and the protein content in the protein isolates was greater than 90%. Solubility, emulsion activity index (EAI), emulsion stability index (ESI), foaming capacity (FC) and foam stability index (FSI) of the protein isolates were affected by pH, all of them were minimal at isoelectric pH range (pH 4-5), and increases toward both ends of pH scale. The water absorption average was 2.46 mL/g of protein and no significant difference (p<0.05) between them.Lupinus spp.,protein isolate had greater oil absorption (4.69 mL/g protein), whereas the L. splendens Rose protein isolate had highest EAI at all pH values, except pH 2, and L. albus protein isolate showed the highest ESI at all pH values, except at pH 5 and 8. L. splendens Rose protein isolate had greater FC at all pH values,but L. albus protein isolate had higher FSI at all values of pH, except pH 10.The gelling minimum concentration was 7.5, 9.0 and 11% w/v for the protein isolates from L. albus, L. splendend Rose and Lupinus spp., respectively. Thus the protein content as some functional properties of the protein isolates obtained from different Lupinus seeds, are similar to those having the soy protein isolates, primary source for obtaining commercial of these additives in the food industry.