Polysaccharide gels physical properties

Robinson, G., Manning, C. E., and Morris, E. R. (1991). Conformation and physical properties of the bacterial polysaccharides gellan, whelan, and rhamsan. In Food Polymers, Gels and Colloids, p. 31. Royal Chem. Soc., London. 

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%. 

The study of the interactions of pectins with metal ions in aqueous solution greatly contributes to the comprehension of the properties of their solutions and gels at molecular level. These acidic polysaccharides also manifest a cooperative-sequential binding mechanism for divalent cations [12, 14]. The most characteristic physical property of pectinic... 

Pectins are mixtures of polysaccharides that originate from plants, contain pectinic acids as major components, are water soluble, and are able to form gels under suitable conditions (See section on Physical Properties). 

Since polysaccharides have polar groups as well as some hydrophobic features, there can be inter residue interactions in a polysaccharide as well, but these attractions are expressed as interactions between different chains giving rise to such phenomena as crystallization which is prominently expressed in chitin and in cellulose. Other types of polysaccharides exhibit multistrand helix formation as in the case of sceleroglucan whose tendency for triple helix formation leads to unusual physical properties. Still other types of polysaccharides can form cross links in a more random way leading to gel formation as in the case of pectin, agarose and alginates. Chain interactions in other polysaccharides such as hyaluronan, chondroitin or... 

Starch is a natural polysaccharide that can be derived from inexpensive and renewable resources. Starch films and coatings are primarily used for food packaging. Natural and modified starch films are also used to change the physical properties of food products such as soups and meat products by modifying the texture, viscosity, adhesion, moisture retention, and gel formation (Thomas and Atwell, 1997). Starch molecules are composed of two macromolecules namely amylose and amylopectin. Amylose has excellent film-formabihty, and forms odorless, tasteless, and colorless films. The relative amoimt of amylose and amylopectin depends on the plant source and is a key factor in determining the properties of starch. Generally starch contains 20-25% amylose and 75-80% amylopectin (Jimenez et al., 2012). 

---