Effects of popping and extrusion processes on some hydration properties of Amaranth

The effects of popping and extrusion processes on some of the hydration properties of Amarantus cruentus, which had already been degermed and dehulled, are discussed. Response surface methodology was used to analyse the effect of process variables (temperature and moisture) on hydration properties, evaluated by water solubility (S) and by amylographic retrogradation (R). Results show that precooked flours obtained by popping have a very high suspension consistency with low or intermediate S, while those obtained by extrusion have very high S but a much lower suspension consistency. The high S values for extruded samples are even higher than those for extruded waxy types of cereals. The effects of the variables on each response depend on each case. S increases as temperature (T) and moisture (M) increase in both processes, although in extrusion, a maximum value was observed at 200 degreesC and about 15% M. On the other hand, an inverse variable effect is observed for R; a minimum value is observed with extruded samples at about 14% M and for the whole T range, while a typical saddle-shaped surface is obtained for popped samples, with maximum values found at about 14% and 18% M for the two extreme T values, the highest and lowest, respectively. Another interesting effect is that the S-R pair values corresponding to popped samples do not fit the correlation between S and R, normally found with extruded samples. We can conclude that with the application of both processes it is possible to obtain precooked flours that have a wide range of hydration properties.