Effect of cold plasma on structural and rheological properties of Guar gum

In this work, the physicochemical properties of commercial guar gum powder were investigated after air atmospheric pressure cold plasma treatment at three different times (5, 10 and 15 min). The results of steady shear flow test showed that behavior of both control and cold plasma treated samples was pseudoplastic. Among the rheological models, the Hershel bulkley model had higher coefficient of determination (R2). The nH in the control and treated samples was less than 1. Also, KH decreased significantly with time (except 5 minutes). In strain sweep, storage module G′ and loss module G″ decreased significantly as the time increased. The crossover point (G′=G″) of 5 minutes treated sample for 5 minutes was higher than the control samples, which decreased with increasing the treatment time. In the low frequency range of frequency sweep, G″ module of the control and treated samples was higher than G′ module. From the frequency of 0.1 to 1 Hz, the G′ and G″ modules depended on the frequency. After crossover, the G″ module prevailed over the G′ module and the guar gum showed weak gel behavior. The value of tanδ in samples was less than 1 and higher than 0.1. The complex viscosity (η*) significantly decreased, as the time of treatment increased. The slope of complex viscosity decreased with the increasing time. The FTIR data demonstrated that the absorption spectrum of the treated samples was similar to the control one.