Background Gellan gum (E418, CAS 71010–52–1) is a polysaccharide from brown algae (Sphingomonas (formerly Pseudomonas) elodea) with β1→4 type tetrasaccharide repeats cross linked by α1→3 glycosidic bonds. Due to these non α1→4 type linkages, E418 is suitable for gel preparations which bear low aspiration risks for special patient groups, notably dysphagia patients.
Purpose The aim of this work was: to quantify the rheological and texture modification of E418 as a function of concentration, pH, conductibility and temperature; and to elucidate the complex material behaviour of E418 semisolids in view of their application for dysphagia patients.
Material and methods Aqueous semisolids of E418 (Gelzan, Sigma Aldrich G1910) were prepared at concentrations between 0.1% and 2.0%, and at temperatures of 50–90°C. Viscosities were measured at the yield point using a Brookfield R/S+ rheometer equipped with a Vane spindle 30/15. Textures were measured on a Brookfield CT3 TexturePro Analyser using the TA15/1000 30 mm D, 45° cone at a penetration depth of 20 mm.
Results E418 remains tasteless below a 2% concentration. Excessive heat, extreme pH and low ionic strength have a negative impact on gelification. Tap water is suitable for E418 preparations. Temperature of no more than 70°C is a compromise between hydration (solubilisation) and degradation of E418. pH <3 is incompatible with E418.
Using tap water of 0.512 mS/cm and 18°fH, gel viscosity increases linearly with raising E418 concentration from 220 mPa*s at 0.1% to 6044 mPa*s at 2% with least square line y=2905x-289 (r = 0.98). Hard tap water of 0.519 mS/cm and 27°fH yields a calibration line of y=11129x-206 (r = 0.995). Its texture increases polynomially from 149 g at 0.5% to 430 g at 1.5% with y=89 × 2+124x (r = 0.93), respectively.
Conclusion E418 semisolids need a standardised preparation method to bring viscosity into a predefined range. A correlation line specific for the tap water source helps to find individually optimised E418 concentrations for special patients, such as those suffering from swallowing diseases.
References and/or Acknowledgements This work was funded by Bangerter-Rhyner-Foundation (grant F.006514-42-ERBQ-01) and Swiss Food Research (grant F.006514-42-ERBQ-02)
No conflict of interest.
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