Modulating the hydration properties of pea hull fibre by its composition as affected by mechanical processing and various extraction procedures

Abstract

From a technological point of view, the application of dietary fibre in foods is mostly related to their water-binding properties. Hydration properties are affected by several factors, of which the particle size and composition are the most relevant. In the present study, pea hulls were used as an example of a fibre source with a complex cellulosic rich cell wall structure containing low-methoxylated pectin. The goal of this work is to study the impact that the extraction of soluble compounds by several treatments exerts on the morphology, chemical composition and hydration properties of samples with a specific and narrow particle size distribution (i.e. ‘fine’ and ‘coarse’). Evaluated treatments were: incubation in water, in ethanol, in hot acidic conditions and with a chelating agent. The processed fibres were characterized in terms of gross composition, sodium content, neutral sugar profile, microstructure and water- binding properties. Incubating pea hulls with ethanol or water resulted in an increased total dietary fibre content and similar hydration properties. Pectin acidic extraction loosened the rigid cell wall matrix, increased the amount of soluble of the remaining fibre and enhanced water-binding properties. Chelating assisted pectin extraction presented the highest water-binding properties due to the formation of pectic-related sodium carboxylate structures that favoured the water uptake. Fine fibres contained a higher amount of soluble dietary fibre than the respective coarse ones. The present study highlights that the hydration properties of PHF can be markedly improved using pectin targeted chemical extraction procedures.