Effects of amylopectin structure and molecular weight on microstructural and rheological properties of mixed beta-lactoglobulin gels

Abstract

Nongelling amylopectin fractions from potato and barley have been used to form mixed â-lactoglobulin gels. The amylopectin fractions were produced by varying the time of R-amylase hydrolysis followed by sequential ethanol precipitation. The molecular weights, radius of gyration, chain length distribution, and viscosity of the fractions were established. The mixed gels were analyzed rheologically with dynamic mechanical analysis in shear and microstructurally with light microscopy, transmission electron microscopy, and nuclear magnetic resonance spectroscopy. The result of the gel studies clearly showed that small differences in the molecular weight of amylopectins have a significant influence on the kinetics of protein aggregation and thereby on the gel microstructure and the rheological behavior of the gel. Both an increase in the molecular weight and a higher concentration of amylopectins resulted in a more open protein network structure, with thicker strands of larger and more close-packed â-lactoglobulin clusters, which showed a larger storage modulus. The transmission electron micrographs revealed that degraded amylopectins were enclosed inside the protein clusters in the mixed gels, whereas nondegraded amylopectin was only found outside the protein clusters. The volume-weighted mean value of the molecular weight of the amylopectins was found to vary between 3.2 × 104 and 5.0 × 107 Da and the ratio of gyration between 14 and 61 nm. The maximum in chain length distribution was generally somewhat distributed toward longer chain lengths for potato compared to barley, but the differences in chain length distribution were minor compared to those seen in the molecular weight and ratio of gyration between the fractions.

Published in

Biomacromolecules
2003, volume: 4, number: 5, pages: 1400-1409

SLU Authors

• Frigård, Tuomo

  • Department of Molecular Sciences, Swedish University of Agricultural Sciences
    

• Andersson, Roger

  • Department of Molecular Sciences, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Physical Chemistry
Organic Chemistry

Publication identifier

• DOI: https://doi.org/10.1021/bm030038e

Permanent link to this page (URI)

https://res.slu.se/id/publ/39577