Pectin gel formation

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. 

The first coherent hypothesis of pectin gel formation and elucidation of the importance of each component were made about 20 years ago by Olsen (f5). 

Much attention has been paid to the pectin-calcium system because of its application in the food industry as gelling agent. A large body of the litterature on this subject is devoted to the gel formation as function of calcium concentration, pH and temperature [1-8]. There were also some reports on the... 

Some Structural Aspects of the Gel Formation of Pectins and Related Polysaccharides... 

The kinetic behavior and microstructure of citrus pectin gels in 60% Sucrose were investigated by transmission electron microscopy (TeM). Ca + addition at Ph 3.0 resulted in faster gel formation. (Adapted from Lofgren et ah, 2005)... 

We believe that single molecule imaging can contribute to a more thorough understanding of the role of pectin in the cell wall. Our future efforts will be focused on pectin gels formed in the presence of calcium. Eventually, it should be possible to visualize side chains on pectin and determine how rhamnose residues in the rhamnogalacturonan backbone of tobacco pectin disrupt the formation of helical regions. 

Gel formation by pectins can be a positive quality factor in some citrus products, for example, gelled citrus salads... 

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... 

Even if the networks of gels have similar length scales, the kinetics of gel formation can be quite different both with regard to the molecular composition and the conditions during gel formation. This will be demonstrated by a comparison of kappa-carrageenan and pectin. They both form transparent gels at very low polysaccharide concentrations and water can apparently be solidified yet without changing its physical properties by gel formation at a polysaccharide concentration below 1%. 

Marudova M, MacDougall AJ, Ring SG. Pectin-chitosan interactions and gel formation. Carbohydr Res 2004 339(11) 1933— 1939. 

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