Functional, rheological, and microstructural properties of hydrothermal puffed and raw amaranth flour suspensions

The pseudocereal amaranth is commonly used in food as whole puffed grain. To improve the utilization of amaranth, hydrothermally treated suspensions of puffed and raw Amaranthus caudatus flour and their blends were investigated in this study. The suspensions were hydrothermally treated at 20, 50, and 80°C for 1, 5, and 24 h. The blends were treated at 80°C for 1 h. The effect of hydrothermal treatments of the suspensions on their morphological (color, SEM), water-binding, and rheological-functional properties was studied. The puffed amaranth suspensions exhibited cold swelling properties by rapid viscosity increase and significant water absorption properties. It was found that hydrothermal treatment at 80°C for 1 h significantly increased water absorption and viscosity in puffed and raw flour suspensions. However, the puffed suspensions showed significantly higher values in water binding and viscosity. Suspensions of raw amaranth flour showed increasing color differences with increasing temperature. Blends of raw and puffed amaranth flour resulted in a decreasing color change with increasing puffed flour content. Water absorption of the samples increased with an increasing puffed flour content. Raw amaranth flour and the 50/50 (puffed/raw) blend had the lowest, 10/90 and 20/80 (puffed/raw), and showed similar viscosity profiles to suspensions of pure puffed flour.