Microwave Effect on the Gelatinized Conditions on Tapioca and Glutinous Rice Starches

Abstract

Microwave effect on starch gelatinization was studied by using tapioca starch and glutinous rice starch as raw materials. Starch samples were heated in the microwave at 2450 MHz in various initial moisture content (13, 15, 20, 25 and 27%) and heating times (0, 3.5, 5, 5.8 and 10 min). Heating was done in the range of 78^o-143^oC for tapioca starch and 78^o-146^oC for glutinous rice starch. The retained moisture content of microwave heated starch were 6.90-19.76% for tapioca starch and 7.08-19.61% for glutinous rice starch. Regarding to the gelatinization of starch, it was found that the microwave affected starch to gelatinize. Expressing the gelatinization as degree of gelatinization (%DG), it was shown that the %DG of tapioca starch was 15.00-82.88 while the %DG of glutinous rice starch was 10.80-77.38. The %DG had correlation coefficient (r) to the heating time (x₁) and the initial moisture content (x₂) 0.7947 and -0.1620, respectively, for tapioca starch, and 0.8465 and -0.2554, respectively, for glutinous rice starch. The multiple regression of the %DG as a response (Y) due to factor x₁ and x₂ at the second order was also studied. For tapioca starch, Y = 131.891609+26.263387x₁+7.370923 x₂+0.628992 x_1²-0.0306 x_2²-1.275157X₁X₂ (r²=0.940 at P £0.05), and for glutinous rice starch, Y=17.221115-3.177827 x₁+0.032624 x₂+0.198334 x_1²+0.003831 x_2²+0.003256 X₁X₂(r²=0.965 at P £0.05), were resulted.