While fibrous byproducts are abundant, using them in food products to improve food nutrition and quality without degrading taste or texture can be challenging. Citrus fiber has been shown to have high water holding capacity and apparent viscosity. However, to better incorporate citrus fiber into foods, their rheological properties, and composition, need to be better understood. Pectin was found to be 42% of the composition of the citrus fiber evaluated in this study. The theological properties of citrus fiber solutions were clearly non Newtonian and the type of model that best fit the citrus fiber varied depending on its particle size. Particle size of citrus fiber also significantly changed the apparent viscosity of their solutions. As citrus fibers hydrate, the fibers swell, which was illustrated by microscopic imaging. (C) 2013 Elsevier Ltd. All rights reserved.