Global Structures of High Methoxyl Pectin from Solution and in Gels

Images of high methoxyl orange pectin deposited from solution and high methoxyl sugar acid gels (HMSAG) were obtained by atomic force microscopy (AFM) in the tapping mode. For the first time, images of pectin deposited from water revealed that the transition from pectin networks to individual molecu...

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Bibliographic Details
Published in:Biomacromolecules 2007-02, Vol.8 (2), p.573-578
Main Authors: Fishman, Marshall L, Cooke, Peter H, Chau, Hoa K, Coffin, David R, Hotchkiss, Arland T
Format: Article
Language:English
Subjects:
Applied sciences
Citrus sinensis
Exact sciences and technology
Gels
Mechanics
Microscopy, Atomic Force
Molecular Conformation
Natural polymers
Pectins - chemistry
Physicochemistry of polymers
Solutions
Starch and polysaccharides
Sugar Acids
Water
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Summary:Images of high methoxyl orange pectin deposited from solution and high methoxyl sugar acid gels (HMSAG) were obtained by atomic force microscopy (AFM) in the tapping mode. For the first time, images of pectin deposited from water revealed that the transition from pectin networks to individual molecules or aggregates thereof occurred at concentrations between 6.5 and 13.1 μg/mL. At 6.5 μg/mL, shapes included rods, segmented rods, kinked rods, rings, branched molecules, and dense circular areas. At 13.1 μg/mL, all of these shapes were integrated into networks. These same structures were discernible in pectin high methoxyl sugar acid gels. Thus one might consider pectin networks in water at concentrations in excess of 10 μg/mL to be separate fluid precursors of networks in high methoxyl sugar acid gels. Examination of AFM images revealed that gels with “uniform” distribution of strands and pores between strands had higher gel strengths as measured by a penetrometer than gels in which strands were nonuniformly distributed and were separated by large and small spaces.
ISSN:1525-7797
1526-4602
DOI:10.1021/bm0607729