Characteristics of normal and waxy corn: physicochemical, protein secondary structure, dough rheology and chapatti making properties.

Abstract

The physicochemical, protein secondary structure, dough rheological and chapatti making properties of normal and waxy corn types were evaluated. Waxy corn grains showed the highest L* and b* value, while red-pigmented corn grains had the highest a* value. Higher accumulation of K, Mg, Na and Ca minerals in corn was recorded, while Cu, Mn, Fe and Zn were present in trace. Meal prepared from waxy corn had higher L*, a* and b* values as well as ash, protein and fat content. A significant decrease in various mixograph parameters was observed with increase in water level during dough development. A decrease in dynamic rheological parameters (G', G'' and tan δ) of dough from all corn types was recorded with increase in water level. Dough developed from waxy corn meal had lower G' and G'' as compared to that from normal corn types. FTIR spectra of dough from different corn types at different water levels showed various peaks in amide-I region with most prominent peak at about 1650cm-1 followed by 1640-1645 and 1610-1620cm-1 regions. The peak intensities increased with increase in water level which was an indicative of the increase in intermolecular and antiparallel (IM+AP) β-sheet as well as α-helix and β-sheet structures. Dough developed from waxy corn showed change in peak intensities at high moisture level only. The chapatti made from normal (yellow) corn showed higher consumers' acceptability score, while that from waxy corn was poor.