Effect of stirring speed on low acyl gellan gum fluid gels’ rheology, particle morphology and physical ageing

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  • Gabriele D'Oria
  • Xinyue Zeng
  • Hans Joerg Limbach
  • Christoph Hartmann
  • Ahrné, Lilia
  • Deniz Z. Gunes

Fluid gels are jammed suspensions of gelled particles widely used across several industries to functionalise materials. They can be obtained for example by applying shear to a gelling hydrocolloid during its sol-gel transition. In the present study, the impact of flow rate, modulated by applying different processing stirring speeds under constant geometrical parameters, on the rheology, particle morphology and physical ageing of low acyl gellan gum fluid gels was investigated. Fluid gel particle elongation was observed in samples processed at higher stirring speeds whereas, no decrease in particle size was measured. The increase in aspect ratio is attributed due to the flow rate experienced by the particles through the geometry used to manufacture the samples. Fluid gels processed at higher stirring speeds generally showed lower low-shear viscosity, elastic modulus and higher yielding properties and interconnectivity. This might be due to the elongation of the fluid gel particles which would decrease particle voluminosity but increase the likelihood of mechanical entanglement, increasing their viscous dissipation. In addition, samples manufactured at higher stirring speeds exhibited a G′ increase with the number of shear cycles performed whereas, samples processed at lower stirring speeds showed a G′ decrease with the number of shear cycles performed. This behaviour might be caused by the balance between two counteracting mechanisms: abrasion (decrease in G′) and compaction (increase in G′). In addition, the higher the stirring speed the higher the ageing exponent. This might be due to the larger surface area of elongated particles which might ease interparticle link formation. Furthermore, the impact of the gravitational field on the physical ageing of low acyl gellan gum fluid gels was investigated by entrapping silica microparticles within the fluid gel particles, allowing tuning the density difference between the continuous and dispersed fluid gel phases. Finally, this study helps providing a better understanding on how processing stirring speed could be used to tune fluid gels’ properties for specific industrial applications.

Original languageEnglish
Article number109614
JournalFood Hydrocolloids
Number of pages11
Publication statusPublished - 2024

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© 2023 The Authors

    Research areas

  • Ageing, Fluid gel, Particle morphology, Processing, Rheology

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