Study On The Phase Behavior Of Carrageenan/Gelatin Mixture

Biopolymers alone cannot satisfy fine structure, various texture, novel flavor and other specific functionality requirements for the modern foods due to their limited species and relatively simplex chemical structure. Phase separation of biopolymers mixture can enrich and optimize the microstructures and hence rheology properties, as well as peculiar characteristics of desired food products. The phase behavior of sodium type carrageenan(κ-, ι-, λ-carrageenan) and type A, type B gelatin were studied using micro Differential Scanning Calorimetry(micro DSC), thermal scanning rheology and turbidity measurements on cooling under different ion species and ion strength. Phase separation can be classified into aggregative and segregative ones. By observing conformational orderings, gelation and phase behavior, ion strength-temperature phase diagram of 0.75wt%carrageenan/0.75wt%gelatin mixture was built up. Microstructural change of the mixed system was observed by Scanning Electron Microscope(SEM), Confocal Laser Scan Microscopy(CLSM) and Zetasizer Nano-ZS. The mechanism of associative phase behavior and the effect of p H, ionic strength, temperature, polymer concentration and mixing ratio on the phase behavior were examined. The main conclusions were as follows:1. High purity of sodium form carrageenans are prepared by using ion-exchange resin. Helix structure forming ability of carrageenan: κ-carr > ι-carr >> λ-carr. Conformational orderings and gelation of carrageenan are dependent on ion species and ion strength, while those of gelatin are independent of them. Both of gelling temperature and gel strength of gelatin are low.2. Biopolymers impeded the helix aggregation of each other due to the space limitation. Phase diagram can be divided into six regions: I) compatible region; II) segregative phase separation(SPS); III) electrostatically induced associative phase separation(EIAPS); IV) hydrogen bonding induced associative phase separation(HBIAPS); V) coexistence of EIAPS and HBIAPS; VI) coexistence of HBIAPS and SPS. p H prominently affects the phase diagram boundary via the changes of the quantity and density of electric charge.3. p H, ionic strength, mixing concentration and ratio are the major parameters that affected the hydrogen bonding reinforced complex coacervation. Associative phase separation dominated by hydrogen bonding or electrostatic interaction will be totally imputed when p H > 10.0, mixing concentration is below 0.4%, or ion strength is above 300 m M. The ratio of 0.2 indicates a stoichiometry of the complexation of gelatin with κ-carr. Hydrogen bonding reinforced complex coacervation exhibits a maximum transition temperature around Na Cl = 150 m M. Their effects should be explained in the context of electrostatic complexation. Electrostatic complexation seems to be a prerequisite or at least an advantage for the subsequent formation of hydrogen bonding upon cooling.