In situ real-time rheological characterization of alginate gelation

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One challenging issue in rheology is to characterize materials undergoing fast transient structural changes during a physical process such as the gelation of polysaccharides. To investigate the kinetics of such a process, reliable real-time rheological monitoring is required. The scientific objective of this research project is to elucidate the gelation kinetics of alginate by means of a novel rheological approach. The impact of the polysaccharide concentration, the molar ratio of calcium to carboxylate ions, the cation type, and the ionic strength will be studied in situ by performing an instant infusion of divalent cations into the samples. To achieve such an infusion, the rheometer base, where the alginate solutions will be placed, must be modified. To provide a proof for our concept, the custom-made prototype base has been successfully tested using aqueous solutions of 1 and 1.5 wt.% alginate. The instant response of the polysaccharide to the presence of the calcium ions could be successfully recorded. In addition to the in-situ rheological characterization, the microstructural changes will simultaneously be recorded using optical microscopy. The combined approach can provide new insights into the gelation kinetics of alginate. The findings of this study are also of industrial relevance as this natural polysaccharide is used in many applications in the food, cosmetic, and pharmaceutical industries.