Cellulose and starch are both renewable biomass and have been extensively used to form hydrogels modulated by concentration, pH, or in presence of additives, such as salt, surfactants 1-2. Well-dispersed oxidised cellulose nanofibril (OCNF) hydrogels possess promising shear-thinning properties for formulation applications3. We aimed to investigate gel properties (via rheology studies) of OCNF-starch based hydrogels in the presence of various concentrations of NaCl. OCNF (1wt%) and soluble starch (0.5 and 1 wt%) were blended to prepare hydrogels, where addition of starch to the OCNF resulted in stronger rheological properties compared to the OCNF and starch gels alone. Starch polymers (mainly linear amylose) were suggested to form interpenetrating networks with cellulose fibrils. The stiffness and viscosity of OCNF-Starch hydrogels were further enhanced by the addition of NaCl (up to 0.5 wt%). Increased ionic strength within the gel network disrupts the double layer of the charged particles allowing more intense interaction between fibrils and amylose structure. However, at higher ionic strength (i.e. 0.75 wt% NaCl content) the OCNF-Starch gel strength appears to reduce due to the formation of larger aggregated gel networks (hence, precipitation). ζ-potential and SAXS analyses were also conducted to confirm surface charge and fibril network structure in order to provide an in-depth understanding of the OCNF-Starch gel network, which has potential to be utilised as a rheological modifier in food, personal and healthcare products.

Monovalent salt induced gelation of oxidised cellulose nanofibrils and starch networks

2019 Spring National Meeting

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