Gelatin solutions and gels

Bohidar H. B., Maity S., Saxena A., Jena S. Dielectric behaviour of Gelatin solutions and Gels. Journal Colloid Polymer Science 276,1 (1998) 81-86. 

Maquet J, Theveneau H, Djabourov M, Leblond J, Papon P. State of water in gelatin solutions and gels An 1H n.m.r. investigation. Polymer 1986 27(7) 1103-1110. 

Amis, E. J., Janmey, P. A., Ferry, J. D., and Yu, J., 1983, Quasi-elastic light scattering of gelatin solutions and gels. Macromolecules 16 441-446. 

E.J. Amis, P.A. Janmey, J.D. Ferry and H. Yu, "Quasielastic Light Scattering Measurements of Self-Diffusion and Mutual Diffusion in Gelatin Solutions and Gels, Polvm. Bull. (Berlin). 6, 13-19 (1981). 

E. J. Amis, P. A. Janmey, J. D. Ferry, and H. Yu. Quasielastic light scattering measurements of self-diffusion and mutual diffusion in gelatin solutions and gels. Polymer BmZ/., 6 (1981), 13-19. 

In general, derivatization increases solution and gel clarity, reduces the tendency to gel, improves water binding, increases freeze—thaw stabiHty, reduces the gelatinization temperature, increases peak viscosity, and reduces the tendency to retrograde. Combinations of substitutions are used to obtain desiredproperti.es for specific appHcations. 

These two characteristic qualities of the gels are best interpreted on the assumption that the disperse phase does not consist of isolated particles but that union between a number of these particles takes place to form relatively short fibrils of threads, which intersect one another to form a felt in the irregular meshes of which the mobile liquid phase penetrates. The fibrils in the case of gelatine would, according to Bancroft, consist of a viscous water in gelatine solution, and, according to Hardy, a solid solution of water in gelatine. 

Water soluble polymers behave like other solutes, i.e. radiation interacts with water principially and products of radiolysis react with the polymer. If the polymer is composed from different meres, what is the case with biopolymers, different segments of the polymer can have different rate constants of reaction with water derived radicals, c.f. the case of gelatin zols and gels [8], The radiation chemistry of polymers dissolved in water is the chemistry of reactions with OH, H, eaq, H2O2 and not, sensu stricto, of the polymer itself. Experiment shows clearly, that the radiation chemistry of the same polymer, but in the dry or almost dry state is completely different from radiation chemistry of its aqueous solution. Spurs are formed in the dry polymer and not in water. 

A distinct difference between the cooling curve of gelatin solutions and that of pure water was established by Lottermoser and Matthaes. A positive heat effect was also found by other authors Hardy showed that heat is evolved upon gel formation from azomethine solutions. Similar results have been obtained for gelling soap solutions ... 

One of the methods to determine the gd point is the determination of properties such as the storage modulus at a certain firequency as a function of time at a certain temperature or as a function of temperature, when the network formation is apparently instantaneous. The instant or temperature where the storage modulus rises from immeasurably low values is a measure of the gel point - the gel time or the gel temperature - respectively. Another way is to determine the point where the storage and loss moduli cross each other as a function of time or temperature. Te Nijenhuis [11,23,24] made use of the first method to determine the gel point and the maximum gelation temperature of gelatin solutions. Ross-Murphy [9] analysed both methods for the determination of the gel point of aqueous gelatin solutions and concluded that they ate rather inaccurate. 

Complex Coacervation. This process occurs ia aqueous media and is used primarily to encapsulate water-iminiscible Hquids or water-iasoluble soHds (7). In the complex coacervation of gelatin with gum arabic (Eig. 2), a water-iasoluble core material is dispersed to a desired drop size ia a warm gelatin solution. After gum arabic and water are added to this emulsion, pH of the aqueous phase is typically adjusted to pH 4.0—4.5. This causes a Hquid complex coacervate of gelatin, gum arabic, and water to form. When the coacervate adsorbs on the surface of the core material, a Hquid complex coacervate film surrounds the dispersed core material thereby forming embryo microcapsules. The system is cooled, often below 10°C, ia order to gel the Hquid coacervate sheU. Glutaraldehyde is added and allowed to chemically cross-link the capsule sheU. After treatment with glutaraldehyde, the capsules are either coated onto a substrate or dried to a free-flow powder. 

Bohidar et al. 1998, realized studies of Sol and Gel state properties of aqueous gelatin solutions of concentrations 4%, 6%, 8% and 10% (w/v) were investigated through dielectric relaxation studies done at various temperatures in the range from 20 to 60°C carried out over a frequency range 20Hz-10MHz and no relaxation of any nature was observed. 

Olivares et al. (2006), studies performed viscometers very dilute gelatin solutions with concentrations between 10-5 and 10-3 g/cm3, where either intermolecular aggregation or intramolecular folding are possible, respectively, and the sol-gel transition is not observed. 

By measuring the optical rotation as it changes with time, after a gelatin solution is rapidly cooled to the temperature of interest, and extrapolating back to zero time, one can determine the initial specific rotation. It is approximately constant with the concentration, but varies with temperature. This initial specific rotation probably represents that of the sol molecule at that temperature before it is converted into the gel form. 

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