3.2. Cold water solubility and water absorption
The results of cold water solubility and water absorption are
given in Table 2. Acetic acid dissociates in water and produces proton
resulting in reduced pH (see Table 1). The proton can destabilize
and depolymerize glycosidic bonds of the starch molecules.
This effect is enhanced with addition of acetic acid content and
exposure time. Therefore, smaller molecules are formed as a result
of starch degradation. These molecules are generally more soluble
in water and have lower water absorption capacity. Therefore, the
cold water solubility of PGWS and PGCS increased significantly
(P < 0.05) as the concentration of the acetic acid and exposure time
increased. However, water absorption of both samples reduced
with addition of acetic acid. Increasing the exposure time from
0.5 to 24 h enhanced cold water absorption since over the longer
experiment time more interactions between water and starch
molecules may occur. The results are in agreement with previous
results of Majzoobi and Beparva (2014) and Majzoobi et al.
(2014b) who added different organic acids including acetic acid
to native and cross-linked wheat starches and Majzoobi et al.
(2015) who added different concentrations of L-ascorbic acid to
PG maize and wheat starches.