Effects of gamma irradiation on some physicochemical and rheological properties of Persian gum and gum tragacanth

In the present study, the effect of various levels of gamma irradiation (0, 4, 8, 16, 30 kGy) on some physiochemical and rheological properties (FTIR, color, pH, water absorption capacity, solubility, stabilizing capability, flow behavior, apparent viscosity, intrinsic viscosity, molecular weight) of powder form of Persian gum (PG) and gum tragacanth (Astragalus campatus gum: ACG) was evaluated. FTIR analysis, intrinsic viscosity and molecular weight were determined to provide more structural information. Based on our FTIR findings, the functional groups were not significantly affected by gamma irradiation. However, it induced significant changes in color, solubility and water absorption capacity (WAC). In terms of PG, the increase in irradiation dose of (4 kGy) almost doubled its apparent (from 19.9 to 33.4 mPa s) and intrinsic viscosity (from 3.72 +/- 0.04 up to 8.22 +/- 0.17 dl/g), whereas at higher irradiation doses (>4-8 kGy), these parameters decreased. Nevertheless, for GT, significant decrease for apparent and intrinsic viscosity was seen by increasing the irradiation doses, likely due to decreasing of molecular weight and the reduction of side branches and radiolysis of the glycosidic bonds. In addition, the flow behavior of the dispersions shifted from non-Newtonian to Newtonian one. Furthermore, the highest stabilizing capability of PG was seen at 4 kGy in milk sour cherry mixture whereas no significant effect was seen on ACG. Consequently, one can conclude that gamma irradiation could be potentially used at certain dose, as an effective method, to improve some functional properties such as stabilizing ability of PG but not for ACG. (C) 2015 Elsevier Ltd. All rights reserved.