Gelatin Molecule

Boedtker H., Doty P. 1954. A study of gelatin molecules aggregates and gels. Journal of American Chemical Society 58, 668-983. 

In the case of the rather porous and flexible structure of sodium caseinate nanoparticles, the data show that the interaction with surfactants causes a tendency towards the shrinkage of the aggregates, most likely due to the enhanced cross-linking in their interior as a result of the protein-surfactant interaction. This appears most pronounced for the case of the anionic surfactants (CITREM and SSL) interacting with the sodium caseinate nanoparticles. Consistent with this same line of interpretation, a surfactant-induced contraction of gelatin molecules of almost 30% has been demonstrated as a result of interaction with the anionic surfactant a-olefin sulfonate (Abed and Bohidar, 2004). 

Simple coacervation involves the use of either a second more-water soluble polymer or an aqueous non-solvent for the gelatin. This produces the partial dehydration/desolvation of the gelatin molecules at a temperature above the gelling point. This results in the separation of a liquid gelatin-rich phase in assocation with an equilibrium liquid (gelatin-poor) which under optimum separation conditions can be almost completely devoid of gelatin. 

Citrus oils readily form oxygenated products that are likely to congregate at oil/water interfaces and thereby cause a detectable change in IFT. The aldehydic components of citrus oil could react with the amine groups of the gelatin molecules present in the aqueous phases formed by complex coacervation and thereby affect IFT. In addition to chemical reactions, physical changes can occur at an interface and alter IFT. A visible interfacial film can form simply due to interfacial interactions that alter the interfacial solubility of one or more components. No chemical reactions need occur. An example is the formation of a visible interfacial film when 5 wt. per cent aqueous gum arabic solutions are placed in contact with benzene (3). Interfacial films or precipitates can also form when chemical reactions occur and yield products that congregate at interfaces. 

Proteins crosslinked by formaldehyde are important in photography, the leather industry and in bio-medical sciences. Due to the complex structure of the gelatin molecules (consisting of approximately 20 Afferent kinds of amino acids) and the very low crosslink density, it is not possible to detect crosslink resonances under normal conditions. In order to overcome this problem a 13C enriched formaldehyde is used. By comparison with the chemical shifts of model crosslink compounds it is concluded that the predominant crosslink is formed between the lysine and arginine components in gelatin. A possible mechanism for the reaction between these two amino acid components and the formaldehyde has been proposed 154>. 

As the gelatine-in-water mixture cools, the gelatine molecules are attracted to each other and form a continuous network. In this way, the jelly you eat as a pudding is formed. The kind of gel which you put into your hair is made from water and an oil (Figure 2.37). 

The term parent gelatin, coined by Statchard et al. (1944) to designate the ideal, undegraded, precursor gelatin molecule is defined in Section V. 

Flory and Weaver (1960) have advanced a mechanism for the reversion kinetics, in which they postulate the formation of an intermediate (involving the intramolecular rearrangement of a single gelatin molecule) as the rate-determining step. The intermediate, which may be a helix of the poly-L-proline H-type, is converted rapidly to a three-chain compound helix at a rate sufficiently rapid to have no effect on the over-all rate. The scheme may be represented as follows ... 

Interaction between the gelatin molecules at sufficiently high concentration may result in the build up of large gel-type networks... 

Adsorbed gelatine molecules alone do not show a frequency dependence of surface elasticity (Fig. 6.19), which corresponds to a behaviour of an insoluble monolayers. The presence of surfactants changes the elastic and relaxation behaviour dramatically. With increasing SDS concentration the elasticity modulus (frequency independent plateau value of the elasticity) first increases and then decreases. The dynamic behaviour of the mixed adsorption layer changes from one completely formed by gelatine molecules to an adsorption layer completely controlled by surfactant molecules (Fig. 6.20). A similar behaviour can be observed for CTAB and a perfluorinated surfactant (Hempt et al. 1985). 

Kuhn (129) considered gelatin molecules in warm aqueous solutions to be randomly contracted to near spherical shape, and to yield weak streaming double refraction because of stretching under the shearing... 

Pouradier and colleagues presented evidence that gelatin molecules are chemically linear chain molecules rather than nets (178, 179), but that depending on ionic strength and pH of the solutions these chains are contracted or extended. For example, at the isoelectric point the specific viscosity is at a minimum and increases two to three times when the pH is shifted toward acid or alkaline reactions. 

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