Gelatin gelation mechanism

Patches based on GL and pectin hydrogels were described by Mazzitelli et al. (2013). Hydrogels are formed by taking advantage of the different gelling properties of pectin and gelatin (i.e., ionic and thermal gelation mechanisms), and proposed as transdermal formulations for the delivery of testosterone to overcome the limitation of its low bioavailability due to liver pre-systemic metabolism. 

The aim of this work is to elucidate the mechanisms of gelation of the gelatin gels and to establish the relations between the microscopic structure and the rheological properties. 

Substantial research efforts have been made to relate molecular properties to the structures of the junction zones and provide mechanisms for gel formation. Thus we have models for the formation and alignment of double helices for kappa-carrageenan, formation of triple helices for gelatin and egg box models for calcium induced gelation of alginate and pectin to mention a few examples (Morris 1986 Djabourov... 

Modifications of the native starch form can be made by means of thermal and mechanical treatments where the amount of water has an essential role. Referring to Equation 2.1, when starch is heated at a water volume fraction above 0.9 a pure gelatinization phenomenon (and afterwards gelation and retrogradation) or jet-cooking occurs. On the contrary, when the water volume fraction is low (e.g. below 0.45), a real melting of starch crystallites occurs [11,27] and thermoplastic starch can be obtained [27]. 

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