Effects of stearic acid and gamma irradiation, alone and in combination, on pasting properties of high amylose maize starch

The effects of stearic acid and gamma irradiation on pasting properties of high amylose maize starch (HAMS) were studied. Stearic acid (0%, 1.5%, and 5%) was added to HAMS, and then irradiated at 0, 30, and 60 kGy before pasting. Stearic acid increased the paste viscosity of un-irradiated HAMS from 420 mPa s to 557 and 652 mPa s for 1.5% and 5% stearic acid, respectively. This observation related well with the formation of type II amylose-lipid complexes, with melting temperatures of about 100-120 °C. Gamma irradiation (30 and 60 kGy) reduced pasting viscosity of HAMS. Pasting of gamma irradiated HAMS resulted in the formation of type I amylose-lipid complexes, with melting temperatures and enthalpies ranging from 82 to 102 °C and 0.22 to 1.85 J/g, respectively. Stearic acid addition followed by irradiation creates means of producing different types of amylose-lipid complexes from HAMS for industrial utilization.