A comparative study on the rheological and thermogelling properties of chitosan/polyvinyl alcohol blends in dairy products. (October 2019) - Taherian, Ali R.
Abstract: The present work described physicomechanical properties of three blends of commercial chitosans (A, B, or C) with polyvinyl alcohol (PVA). Chitosans at concentration of 20 g/L and 30 g/L were hydrated in acidic solution and basified with either β-glycerophosphate (β-Gph) or sodium bicarbonate (NaHCO3 ) up to the pH 6.8. Shear and frequency developments of flow and dynamic rheology, the energy of extrusion as gel strength, heat-induced gelation and retention of hydrogels stored in three different mediums were assessed and compared. The primary evaluation showed that the highest molecular weight peaks for chitosan A, B, and C were 136.7 kDa, 163.5 kDa and 51.1 kDa respectively. Increases in both chitosan concentration and temperature resulted stronger and more durable hydrogels. The hydrogels basified with NaHCO3 yielded harder gel than those basified with β-Gph. After 7 days of storage at 37 °C, blend of 30 g/L chitosan A-20 g/L PVA basified with NaHCO3 or β-Gph comprised the highest value of gel strength at 108.9 N s or 97.7 N s correspondingly. It was also observed that hydrogels basified with β-Gph were liquid like at room temperature. Thus, the selection of basifying agent and concentration of chitosan depends upon the application of final product. Highlights: Thermogelling and viscoelasticity of chitosan-PVA varied via basification types. Greater ratio of high molecular weight chitosan provided higher viscoelasticity. Sodium bicarbonate basification revealed stronger thermogel than β-Glycerophosphate. Retention of hydrogel varied based on the type of holding medium.