Composition and Functional Properties of Lupinus campestris Protein Isolates

Abstract

Protein isolates from L. campestris and soybean seeds were prepared using isoelectric precipitation (PI) and micellization (MI) proce­ dures. The amount of protein recovered was considerably higher with the isoelectric precipitation than with the micellization procedure (60% and 30%, respectively). Protein contents were higher than 90% in protein iso­ lates. Anti nutritional factors content (al kaloids, lectins, and tannins) were reduced to innocuous levels after protein isolate preparation. Minimum protein solubility for the precipitated lupin protein isolate (LPI) was at pH 4.0, and between pH 4 and 6 for the micellized lupin protein isolate (LMI), increasing at both extremes of the pH scale. Water absorption for the LMI was 1.3 mllg of protein and its oil absorption 2.2 mllg of protein. The LPI had 1.7 ml/g of protein in both water and oil absorption. Foaming capacity and stability was pH-dependent. Foaming capacity was higher at pH 2 and lower near the protein isoelectric points. Minimum protein con­ centration for gelation in LMI was 8% w/v at pH 4, while for LPI was 6% at pH 4 and 6. Amino acid composition in L. campesrris flour and protein isolates was high in lysine and low in methionine. Most of the essential amino acids in lupin protein isolates were at acceptable levels compared to a reference pattern for infants and adults. The electrophoretic pattern of both protein isolates showed three bands with different mobilities, sug­ gesting that the protein fractions belong to a-conglutin (II S-like protein). ,8-conglutin (7S-Iike protein) and y-conglutin. It is proven that ome of the functional properties of L. campesrris protein isolates are similar to those soybean protein isolates recovered under equal conditions.