Adsorption isotherm studies on the interaction between polyphenols and apple cell walls: Effects of variety, heating and drying

•Binding capacity of polyphenols on apple cell walls can be predicted by Langmuir isotherms.•Binding of charged polyphenols involves hydrogen bonding and ionic interactions with pectin.•Polyphenols selectively bind to different cell walls as a result of diverse wall composition.•Boiling of cell wall...

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Bibliographic Details
Published in:Food chemistry 2019-06, Vol.282, p.58-66
Main Authors: Liu, Dongjie, Lopez-Sanchez, Patricia, Martinez-Sanz, Marta, Gilbert, Elliot P., Gidley, Michael J.
Format: Article
Language:English
Subjects:
(−)-Epicatechin
Cellulose
Chlorogenic acid
Ionic interaction
Non-covalent interaction
Pectin
Phloridzin
Small angle X-ray scattering
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Summary:•Binding capacity of polyphenols on apple cell walls can be predicted by Langmuir isotherms.•Binding of charged polyphenols involves hydrogen bonding and ionic interactions with pectin.•Polyphenols selectively bind to different cell walls as a result of diverse wall composition.•Boiling of cell walls exerts no significant effects on polyphenol binding.•Drying reduces polyphenol-cell wall interactions by hindering access to binding sites. The adsorption capacity of principal phenolic compounds onto cell walls from three apple varieties was investigated. Isothermal adsorption modelled with Langmuir, Freundlich and Redlich-Peterson equations were carried out over a range of concentrations from 0.5 to 30 mM before and after cell walls were subjected to boiling, oven-drying or freeze-drying. The isotherm data were best fitted by the Langmuir model in all cases. Polyphenols selectively adsorbed onto cell walls with maximum binding capacities ranging from 140 to 580 µg/mg cell walls depending on surface charge. Increased pectin in apple cell walls caused a 129%–311% decrease in the adsorption of negatively charged polyphenols, presumably due to electrostatic repulsive forces. Boiling had limited effect on cell wall polysaccharides and polyphenol-cell wall interactions. However, more than twofold reduction in binding capacities of polyphenols was induced after drying by altering the structural (i.e. binding sites) and compositional (i.e. pectin degradation) characteristics of cell walls.
ISSN:0308-8146
1873-7072
DOI:10.1016/j.foodchem.2018.12.098