Effects of gamma irradiation, stearic acid alone and in combination on functional, structural and molecular characteristics of high amylose maize starch

The effects of gamma irradiation, stearic acid alone and in combination on functional, structural and molecular characteristics of high amylose maize starch (Hylon VII) were studied. Stearic acid (0, 1.5 & 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 contents and decreased amylopectin, molecular weight and transition endotherms of the starches due to gamma irradiation. Stearic acid addition also, significantly increased (P ≤ 0.05) water and oil absorption capacities, relative crystallinity as well as decreased swelling power of Hylon VII. Addition of stearic acid to Hylon VII seemed to reduce the effect of gamma irradiation on the solubility and transition endotherms of Hylon VII, even though not statistically significant (P ≥ 0.05). Gamma irradiation, stearic acid addition and in combination did not change the X-ray diffraction pattern and microstructure of Hylon VII. Gamma irradiation had more effect on the molecular structure of Hylon VII compared with stearic acid. Both irradiation and stearic acid alone and in combination did not have any effects on the microstructure of Hylon VII.