Dissolution kinetics of guar gum powders. I. Methods for commercial polydisperse samples

The ability to form molecular solutions, usually referred to as hydration or dissolution, is one of the most important properties of water-soluble polysaccharides and closely relates to their functionality in a plethora of biological and technological processes. The purpose of this study was to investigate the hydration kinetics of four commercially produced guar gum powders using viscosity development as an index of hydration rate. The following three empirical hydration models: (1) first-order kinetics; (2) logarithmic; and (3) the Weibull function, were evaluated for fitting to the hydration rate data of guar gum powders. Of the three models tested, the simple logarithmic function was found to be the most suitable for describing the behaviour of guar gum flours with satisfactory accuracy. By using this model the hydration process can be described by two hydration constants, which can be estimated from a linear plot. However, the hydration rate profile obtained from one guar gum sample of larger particle did not successfully fit any of the above models, producing instead a sigmoidal relationship that was more amenable to a polynomial function.