ABSTRACT
Protein isolates from L. campestris and soybean seeds were prepared using isoelectric precipitation (PI) and micellization (MI) procedures. 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 isolates. Antinutritional factors content (alkaloids, 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 ml/g of protein and its oil absorption 2.2 ml/g 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 concentration 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. campestris 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, suggesting that the protein fractions belong to alpha-conglutin (11S-like protein), beta-conglutin (7S-like protein) and gamma-conglutin. It is proven that some of the functional properties of L. campestris protein isolates are similar to those soybean protein isolates recovered under equal conditions.
Subject(s)
Amino Acids/analysis , Glycine max , Lupinus , Plant Proteins/isolation & purification , Hydrogen-Ion Concentration , Isoelectric Focusing , Lupinus/chemistry , Lupinus/physiology , Micelles , Nutritive Value , Oils/metabolism , Plant Proteins/chemistry , Plant Proteins/physiology , Solubility , Glycine max/chemistry , Glycine max/physiology , Tannins/analysis , Water/metabolismABSTRACT
The functional properties of flours and protein isolates from the legumes Phaseolus lunatus and Canavalia ensiformis were evaluated to determine their potential practical applications. The respective protein isolates were obtained from the flours by using isoelectric precipitation, with a protein content of 71.13% for the P. lunatus isolate (PPI) and 73.75% for the C. ensiformis isolate (CPI). Nitrogen solubility was good in both acid and alkaline pHs for isolates and Canavalia flour (CF), with values as high as 80%, but not for the Phaseolus flour (PF). The flours and protein isolates had good water-holding capacities, with values between 2.65 and 3.80 g/g sample. Oil-holding capacity was highest in PPI (4.59 g/g sample) and CF (3.15 g/g sample). Under alkaline pH, the PPI foaming capacity (147%) was higher than those for CPI and CF, though the flours produced greater foam. Emulsifying activities for the PF, CF, PPI, and CPI were similar (46.78-53.84%) for pH range 6-10. Emulsion stability (ES) was superior in the CF and the CPI, where values reached 100% at pH 7 and 8. Apparent viscosity was pH-dependent.
