Dielectric analysis for in-situ monitoring of gelatin renaturation and crosslinking

This article probes the use of dielectric analysis (DEA) to monitor the physical changes that occur during gelatin renaturation and crosslinking. An interdigitated dielectric sensor was used to monitor ionic mobility in gelatin. In spite of the large concentration of water and ions in the gelatin model systems, a range of frequencies was found where DEA met all the requirements for ion viscosity measurements necessary to monitor aging gelatin. DEA was successful at detecting gelatin renaturation with a remarkably high signal-to-noise ratio. DEA was also capable of detecting crosslinking in the presence of formaldehyde, but only in the special case of fish gelatin. Unlike acid bone gelatin, which is semicrystalline at room temperature, fish gelatin remains fluid. Thus, fish gelatin provides a model system where crosslinking can be monitored in the absence of interference by renaturation processes. The dielectric response was also found to be sensitive to water transport between acid bone gelatin and a simulated pharmaceutical fill made of a PEG 600-water solution. In the case of acid bone gelatin, the kinetics of renaturation as detected from DEA closely matched those measured by monitoring the evolution of the melting point and of the enthalpy of melting as measured by differential scanning calorimetry (DSC). With dynamic mechanical analysis (DMA), the rise in the loss modulus with renaturation also closely tracked the increase in ionic viscosity. (c) 2006 Wiley Periodicals, Inc.