Pectin gelation mechanisms

The HM and LM pectins give two very different types of gels the mechanisms of stabilization of the junction zones in the two cases are described and few characteristics given. The different molecular characteristics (DE, distribution of methoxyl or acetyl substituents, neutral sugar content or rhamnose content) play an important role on the kinetic of gelation, mechanical properties of the gel formed and also on the experimental conditions to form the stronger gels. All these points were briefly discussed. 

Morris, E. R., Gidley, M. J., Murray, E.J., Powell, D. A., and Rees, D. A. (1980). Characterization of pectin gelation under conditions of low water activity, by circular dichroism, competitive inhibition and mechanical properties. Int. J. Biol. Macromol. 2 327-330. 

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 gelling temperature is an important factor for the characterization and application of pectins. The pectin consumer wants a pectin fulfilling his special requirements, this can mean either working with or without pregelation. Pregelation, the weakening of gel structure, occurs when pectin preparations are stressed below their gelation temperature so that the mechanical treatment leads to an irreversible destruction of the three-dimensional network. 

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... 

Studies on the forces that stabilize the pectin gel network have contributed to our understanding of the mechanism of gelation. 

P ectin, a long-chain poljrmeric galacturonide partly esterified with methanol, has been used in the preparation of jellies and similar food products for over a hundred years. The mechanism by which it forms gels is not clearly understood and more information on the factors influencing pectin gel formation is required to develop a more exact theory of gelation. 

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