Potential of alfalfa seeds as a source of protein concentrates for human consumption.

Abstract

Alfalfa (Medicago sativa L.), primarily grown as high-quality forage, contains more than 30% protein in its seeds and represents a promising yet underutilized resource for food applications. This study investigated protein extraction from alfalfa seeds using combinations of saline (0-5% NaCl; S0-S5) and pH (2, 10, and 12; P2, P10, P12, respectively) conditions. Based on yield and purity, water at pH 2 (S0P2), pH 10 (S0P10), and pH 12 (S0P12) was selected. Protein purity did not differ significantly (p > 0.05); however, S0P10 exhibited higher soluble protein content (61.05%) and higher total essential amino acid content (39.23 g per 100 g) than S0P2 and S0P12 (p < 0.05). The pH-dependent solubility of S0P2 (40-70%) remained lower at pH 2, 7, and 9 than those of S0P10 (86-90%) and S0P12 (67-94%) (p < 0.05). The emulsifying activity index ranged from 56 to 71 m² g^-1, with S0P12 exhibiting the highest value (p < 0.05). Emulsion stability was higher in S0P10 (17.5%). Foam stability and foaming capacity ranged from 95 to 97% and 15 to 22%, respectively. The Digestible Indispensable Amino Acid Score (DIAAS) values for S0P10 were higher (p < 0.05) across all groups (0.88 ± 0.03 for infants, 1.50 ± 0.08 for children, and 1.75 ± 0.10 for adults). Trypsin inhibitor activity and saponin content peaked in S0P10 (4.25 TUI mg^-1 and 13.5 mg g^-1), while phytic acid was highest in S0P2 (1.68 g per 100 g) (p < 0.05). Water extraction at pH 10 resulted in higher yields, improved solubility, increased amino acid levels, favorable functionality, and higher DIAAS, establishing alfalfa seeds as a high-quality protein source for human consumption.