Guar gum is a biopolymer that is used in the food industry as a thickener, stabilizer, and edible coating. The aqueous solution of this gum has high viscosity and pseudoplastic behavior. This research aimed to analyze the impacts of sonication at different intensities (0, 75, and 150 W) and time intervals (0, 5, 10, 15, and 20 min) on the viscosity and rheological behavior of guar gum solution. The results showed that the apparent viscosity of guar gum solution (untreated sample) reduced from 0.070 to 0.030 Pa.s with increasing shear-rate from 12.2 s-1 to 134.5 s-1. Also, the apparent viscosity of guar gum solution reduced from 0.046 to 0.021 Pa.s with increasing the sonication time from 0 to 20 min (shear-rate=49 s-1 and power= 150 W). Various rheological equations (Power law, Bingham, Herschel-Bulkley, Casson, and Vocadlo) were employed to fit the empirical values, and the findings of the current study confirmed that the Power law model was the best fit to explain the flow behavior of guar gum solutions. The consistency coefficient of guar gum solution significantly reduced from 0.202 Pa.sn to 0.063 Pa.sn (p<0.05) with increasing sonication time from 0 to 20 min. Furthermore, the consistency coefficient of guar gum solution decreased considerably (p<0.05) while the ultrasonic power enhanced. The flow behavior index of guar gum solution increased significantly (p<0.05) while the intensity and duration of ultrasound treatment increased.
