Time-dependent self-association of spruce galactoglucomannans depends on pH and mechanical shearing

Mamata Bhattarai,Fabio Valoppi,Sami-Pekka Hirvonen,Sami Hietala,Petri Kilpeläinen,Vladimir Aseyev,Kirsi S Mikkonen

doi:10.1016/j.foodhyd.2019.105607

Mamata Bhattarai, Fabio Valoppi + Show 5 more

Open Access

https://doi.org/10.1016/j.foodhyd.2019.105607

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Abstract

The demand for naturally derived, functional and cost-effective raw materials for various food applications is escalating. Spruce wood is a sustainable and abundant, but underutilized source of novel hydrocolloids—galactoglucomannans (GGM). Pressurized-hot water extracted GGM with an intermediate molar mass are hypothesized to form colloidal solutions. To design superior quality products from GGM, an understanding of their colloidal stability and their potential effect in multiphasic systems is required. The present study addresses the functionality of GGM by characterizing their properties in a bi-phasic system, and for the first time, their time-dependent colloidal stability at different extrinsic conditions— pH, ionic strength and after the application of high-intensity mechanical shearing. Amongst the conditions studied, the colloidal stability of aqueous GGM solution was highly pH dependent. The results showed that an intermediate molar mass polysaccharide like GGM formed inter-/intra molecular assemblies, which grew over time, depending on the composition and processing of the aqueous medium. The molecular dispersion of GGM and their dynamic behavior was also compared to solutions of known food hydrocolloids—gum Arabic and hydroxypropylmethyl cellulose. The observed solution properties explain the hydrocolloid functionality of GGM and contribute to design of colloidal polysaccharide systems in food application.

Highlights

A colloidal system is referred to as biphasic system having charac teristics between that of a true solution and suspension
For the characterization of GGM solution properties, our first approach was to understand the differences in the solubility of GGM with that of known food hydrocolloids, gum Arabic (GA) and hydroxypropylmethyl cellulose (HPMC) by comparing their light transmittance in Turbiscan (Fig. 1A)
GGM was highly turbid with only about 63% of incident light being transmitted, compared to 83% and 88% being transmitted through GA and HPMC solutions, respectively

Summary

Introduction

A colloidal system is referred to as biphasic system having charac teristics between that of a true solution and suspension. Literature suggest the size of colloid from 1 nm up to 1 μm (Tadros, 2017). Hydrocolloids, as the name suggests, have hydrophilic colloidal particles and they are widely uti lized to design complex multiphasic food systems that are able to control microstructure, improve shelf-life, or deliver bioactive compounds, for example (Dickinson, 2003). As well as native and modified polysaccharides from plants, animals and mi crobes. Most common plant-based food hydrocolloids are native high molar mass polysaccharides like gum Arabic, pectin, guar gum and konjac gum, as well as modified polysaccharides such as derivatives of cellulose and starch (Dickinson, 2003). The ability of polysaccharides to modify the surface/interfacial activity and form viscous solutions and gels is utilized in the development and stabilization of multiphasic sys tems (Dickinson, 2003). From an application point of view, their solubility in an aqueous medium is an important consideration

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