Relationship between physicochemical and functional properties of amaranth ( A maranthus hypochondriacus ) protein isolates

Summary Protein isolates from six amaranth lines/cultivars ( API s) were evaluated to study their physicochemical (hunter colour, protein content and zeta potential), structural (thermal and conformational) and functional (emulsification, foaming, water and fat absorption) properties. API s had protein content, whiteness index and gel temperature in range of 79.4–85.4%, 41.17–54.26 and 87.8–91.8 °C, respectively. The F ourier‐transform infrared spectra of API s revealed α‐helix, β‐sheets and random coil conformations in the secondary structure. API s with higher relative proportion of β‐sheets had higher D ifferential S canning C alorimeter denaturation temperature and gel temperature. Minimum protein solubility ( PS ) was observed at pH 5.0, indicating isoelectric point (p I ) of amaranth proteins. The PS , emulsifying activity index ( EAI ), emulsifying stability index ( ESI ), foaming capacity ( FC ) and foam stability ( FS ) of API s at neutral p H were related to their zeta potential (ζ). The emulsifying and foaming properties were also determined at different p H s (between 2.0 and 9.0). The EAI ‐p H profile of API s confirmed close relationship between the emulsifying ability and PS .