Amaranth, quinoa and oat doughs: Mechanical and rheological behaviour, polymeric protein size distribution and extractability

Abstract

The rheological characteristics, static and dynamic mechanical properties of amaranth, quinoa and oat doughs and the relative size distribution of their polymeric proteins were evaluated. For the sake of comparison, semolina dough rheological and mechanical properties and the relative size distribution of proteins were also determined. From rheological results it was inferred that the tenacity of amaranth, oat and quinoa dough samples was lower than that of semolina dough. The elastic modulus ( E c ) of amaranth, oat and quinoa doughs was higher than that of semolina dough. Amaranth and quinoa G′ was found to be similar and significantly higher ( p < 0.05) with respect to that of oat dough at a moisture of 30%. The G″ of amaranth, quinoa and oat doughs showed different values. The highest G″ value was recorded for the amaranth dough while the lowest one was shown by oat. For semolina dough, the G′ and G″ values were significantly lower than those of all the other dough samples. Moreover, at low and medium frequencies, tan δ values of oat and quinoa doughs were statistically comparable and significantly lower ( p < 0.05) than that of amaranth and semolina doughs. At high frequencies, tan δ values of investigated samples were different among them and the highest value was detected for amaranth, followed by semolina, quinoa and oat. Results of the size distribution of proteins in amaranth, quinoa, oat and semolina doughs were expressed as the proportion of “unextractable polymeric protein” (UPP). Unextractability of semolina dough proteins (61%) was greater with respect to the others, followed by amaranth (40.7%), oat (24%) and quinoa (10.1%).