Modifications of physicochemical and functional properties of amaranth protein isolate (Amaranthus cruentus BRS Alegria) treated with high-intensity ultrasound

The present study investigated the effects of high-intensity ultrasound (HIUS) on the physicochemical and functional properties of amaranth protein isolates (API). Aqueous dispersions of API (10%) were continuously treated for 15 or 30 min with ultrasound equipment (100 W, 30 kHz) at 30, 60, and 90% amplitudes. The electrophoresis technique demonstrated no changes in the molar masses of the proteins. However, HIUS significantly increased the surface free sulfhydryl groups (SH) and changed the surface hydrophobicity, indicating a breakdown of internal links that maintained the native API structure. Ultrasound reduced the size of the particles in the aqueous dispersions of API, suggesting the dissociation of aggregates from API. The results showed that the solubility in most HIUS-treated API was significantly (p < 0.05) higher than that of the native proteins at pH 7. The energy density of 50 J/cm3 provided the best-combined properties of emulsion formation and stability. These results suggest that HIUS is a useful technology to improve the functional properties of amaranth proteins.