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

Abstract

Summary Protein isolates from six amaranth lines/cultivars (APIs) 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. APIs 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 Fourier‐transform infrared spectra of APIs revealed α‐helix, β‐sheets and random coil conformations in the secondary structure. APIs with higher relative proportion of β‐sheets had higher Differential Scanning Calorimeter denaturation temperature and gel temperature. Minimum protein solubility (PS) was observed at pH 5.0, indicating isoelectric point (pI) of amaranth proteins. The PS, emulsifying activity index (EAI), emulsifying stability index (ESI), foaming capacity (FC) and foam stability (FS) of APIs at neutral pH were related to their zeta potential (ζ). The emulsifying and foaming properties were also determined at different pHs (between 2.0 and 9.0). The EAI‐pH profile of APIs confirmed close relationship between the emulsifying ability and PS.

Effect of ultrasonic pretreatment on physicochemical characteristics and rheological properties of soy protein/sugar Maillard reaction products

“…However, Shevkani et al (2015) showed that proteins from kidney bean and field pea with higher thermal denaturation temperature could produce stronger heat-induced gels, which was different from the results in this research. Similar results were obtained in a recent study on amaranth protein isolates (Shevkani et al 2014). This difference could be caused by the difference between acid-induced and heat-induced gel mechanism.…”

Effect of removal of phenolic compounds on structural and thermal properties of sunflower protein isolate

“…Amide I and amide II are the characteristic bands found in the infrared spectra of proteins, arising from amide bonds. In amide I band, absorption leads to stretching vibration of C=O bond while as, in amide II band absorption leads primarily to bending vibration of N-H bond (Shevkani et al 2014). The secondary structure of protein is very sensitive to the location of both amide I and amide II band, because hydrogen bonding between the different elements of secondary structure involves the both C=O and N-H bonds.…”

Physicochemical and Functional Properties of Vegetable and Cereal Proteins as Potential Sources of Novel Food Ingredients

“…the ability of a protein to form and stabilize the emulsion by creating electrostatic repulsion on oil droplet surface. The emulsion stability index (ESI) refl ects the ability of the proteins to form and maintain a stable emulsion over a period of time by preventing fl occulation and coalescence of the oil globules (9). The soya and maize protein hydrolysate 05 had the lowest EAI of 3936.62 m 2 /g, while the pea fl our had the highest, 52 399 m 2 /g.…”

“…Several authors have compared the physicochemical and functional properties of buckwheat protein, soya protein isolate and casein (5,6,8). The functional characteristics of pseudocereals as quinoa and amaranth have also been reported in literature (5,9,10). Regarding cereals and other oilseeds, some authors have made comparisons among the protein functional properties of rice cultivars, peanut fl our and peanut protein concentrate as indicators of their potential use in food industry (11,12).…”