Huauzontle (Chenopodium nuttalliae Saff.) protein: Composition, structure, physicochemical and functional properties

The physicochemical and functional properties of huauzontle protein isolates (HPI) were investigated. HPI had high contents of most essential amino acids excepting valine, and a protein digestibility of 83.0 +/- 0.2%. SDS-PAGE showed that the main protein bands were located between 20 and 50 KDa. FTIR pinpointed that the Amide I secondary structure was composed by repetitive units (e.g., alpha-helix and beta-sheet), whose relative proportion varied with pH. Foaming capacity (FC) and foaming stability (FS) were higher as HPI concentration increased. FC was 206 +/- 2.8% and FS was 100% after 1 h of aging using 3% HPI at pH 7.0. Self-supporting homogeneous gels were formed at pH 7.0 and 9.0, but not at other pH values. The storage modulus (G') predominated over the loss modulus (G '') over a heating-cooling temperature ramp (20-90-20 degrees C), with both moduli tending to increasing upon heating, and with gel hardening occurring during cooling. G' and G '' decreased sharply at moderate and high strain%, with a crossover of both moduli taking place at lower strain% (similar to 60%) at pH 9.0. This behavior might be attributed to the relative percentage of protein secondary structures which changed with pH. This study clearly establishes HPI as a potential and novel functional ingredient for the food industry, which besides possesses a high nutritional quality.