3.2. Main study: effect of reaction conditions on RS and P contents of
the CL starches
Preliminary cross-linking experiments had shown that a high
content of RS was obtained at higher temperature and pH ranges.
Therefore, for the main study, the reaction temperature and pH
ranges were selected as 38–70 C and 10–12, respectively. The
experimental points for the main study generated by Design Expert
Software, their coded levels and the observed responses (RS and P
contents) for the CL corn and wheat starch samples, are shown in
Table 3.
The RS and P contents of CL wheat starches were significantly
higher than those of the CL corn starches, as revealed by the paired
t-test (p < 0.05). RS contents of the CL starches produced at the low
reaction pH (pH 10 and 10.5) from both types of starches (corn and
wheat) were comparable to the RS content of the respective native
starches. There were no significant differences in the RS contents of
the native corn starch and the CL corn starches produced at pH 10
and 10.5, regardless of the reaction temperature. It was also indicated
in the literature that higher alkaline pH ranges are required