I observed as one may expect depletion interaction between amidated pectin (degree of esterification 28 - 34%, degree of amidation 16 - 22%) in solution (natural pH, deionized water) with dispersed 'monosized' silica (1 µm, 0.2 % m/m). It seems that there is specific interaction at pectin concentration 1 % and below different from pectin concentration 2 % and higher. Maximum content of nonflocculated silica seems highest at 2 %.
Dear colleague,
In my personnel opinion especially concerning polysaccharide in solution, it is very difficult to quantify the interactions occurring in these kind systems, such as this type of macromolecules which have poly-functionalities yielding then, several mechanisms of interactions. However, in dispersed systems, the suitable way which can be helpful for a good resolution about the interactions occurring between the continuous phase, the dispersant and the dispersed particles, is the rheology combined with zeta potential measurement.
I hope that I participated helping you to resolve this situation
Cordially
Interesting! There is clearly great potential for an attractive interaction based on hydrogen bonding between amino groups on the polymer and hydroxyl groups on the silica.
The suitable way which can be helpful for a good resolution about the interactions occurring between the continuous phase, the dispersant and the dispersed particles, is the rheology combined with zeta potential measurement.
Final poster up-loaded
https://www.researchgate.net/publication/282808430_Investigation_of_slow_structuring_processes_in_pectin_solutions__Interaction_of_dissolved_biomolecules_and_particles
it seems that the origin of flocculation is rather due to Ca ions naturally contained in the product, which bridge between dissociated carboxyl groups and the negatively charged SiO2 surface.
Conference Paper Investigation of slow structuring processes in pectin soluti...
It seem this yes, because the esterification of polysaccharide yields a carboxylic function witch can be protonated in the alkaline zone and also the acidic ones ; hence electrostatic intercations inducing therefore a suitable dispersion or other mecansime such as floculation or depletion
Is this really depletion? I would expect amidated pectin to have some affinity with the surface -OH groups of the silica.
Polysaccharides often do not adsorb onto silica. However, pectins are charged and sometimes contain hydrophobic groups. If the 'flocculation' is reversible upon dilution pectin is probably depleted.
I agree with the answer of Remco, effectively this is how polysaccharide interact with this type of systems
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