Fluctuation in the values of pasting parameters of flours among
the varieties may be associated with the variations in the chemical
composition and a-amylase activity. Therefore, the correlations
between the values of pasting parameters and chemical components
were analyzed, and the results are shown in Table 3. Peak,minimum,
final viscosity and setback were positively correlated to starch
content (r ¼ 0.875, 0.710, 0.722 and 0.705, respectively) and negatively
correlated to a-amylase activity (r ¼ 0.474, 0.539, 0.565
and 0.580, respectively). Protein, lipid and fiber did not show
correlation with pasting parameters, while ash was negatively
correlated to peak viscosity and setback.
Flours containing higher starch content displayed higher paste
viscosity. This agreed well with the previous finding that starch had
higher viscosity than flour. Alpha amylase in flour hydrolyzed the
starch granules during thermal gelatinization in the RVA’s canister,
resulting in the decrease of paste viscosity. Therefore, higher
activity of a-amylase gave lower viscosity of flour paste. The data