title: Formation of calcium-mediated junction zones at the onset of the sol-gel transition of commercial kappa-carrageenan solutions.
abstract: Gelling temperatures of commercial kappa-carrageenan solutions were measured using dynamic oscillatory shear rheometry, in response to varying polymer (0.4% to 1.6%, w/w) and added Ca(2+) (5 to 20 mM) salts. Gelling temperatures were found to shift to higher temperatures with increased polymer and Ca(2+) concentration. The Tang model was used to estimate the number of Ca(2+)-mediated cross-links formed with kappa-carrageenan at the onset of junction zone formation. Based on this model, 6 kappa-carrageenan double helices were estimated to be cross-linked by 5 Ca(2+) ions through ionic bridging and electrostatic attraction, within a cross-linking region equivalent to one pitch of the double helix.
authors.affiliation: Dept. of Food and Bioproduct Sciences, Univ. of Saskatchewan, Saskatoon, SK, Canada, S7N 5A8.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Nickerson
authors.forename: Rozina
authors.initials: R
authors.lastname: Darvesh
authors.forename: Allan T
authors.initials: AT
authors.lastname: Paulson
mesh_terms: D002118:Calcium / Q000032:analysis / Q000737:chemistry*; D002236:Carbohydrate Conformation; D002351:Carrageenan / Q000737:chemistry*; D002412:Cations / Q000032:analysis / Q000737:chemistry; D055119:Elastic Modulus; D005503:Food Additives / Q000737:chemistry*; D005782:Gels / Q000737:chemistry; D008956:Models, Chemical; D009994:Osmolar Concentration; D044367:Phase Transition; D044366:Transition Temperature
chemical_list: D002412:Cations; D005503:Food Additives; D005782:Gels; D002351:Carrageenan; D002118:Calcium