Abstract:
The effects of gamma irradiation and stearic acid, alone and in combination, on functional,
structural, and molecular characteristics of high amylose maize starch (Hylon VII, 60%
amylose) were studied. Stearic acid (0, 1.5, and 5%) was added to Hylon VII starch, and then
irradiated at 0, 30, and 60 kGy. Gamma irradiation significantly (p 0.05) increased solubility,
water absorption capacity, and oil absorption capacity as well as decreased swelling power (at 90
and 95°C) of Hylon VII starch. These changes related well with increased amylose and decreased
amylopectin content, decreased MW, and decreased transition endotherms of the starches due to
gamma irradiation. Stearic acid addition significantly increased (p 0.05) water and oil absorption
capacities, relative crystallinity as well as decreased solubility and swelling power of Hylon VII.
Gamma irradiation had more effect on the molecular structure of Hylon VII compared with
stearic acid. Gamma irradiation alone and with stearic acid did not seem to change the XRD
pattern and microstructure of Hylon VII. The similar XRD pattern and morphology observed for
irradiated and non-irradiated Hylon VII suggests that gamma irradiation depolymerizes amylose,
and amylopectin mostly in the amorphous region of the starch to produce less branched or
unbranched amylopectin. Gamma irradiation with stearic acid has potential in Hylon VII
modification.
