Binding of sodium dodecylsulphate to starch polysaccharides quantified by surface tension measurements

The binding of the anionic surfactant sodium dodecylsulphate (SDS) to the starch polysaccharides amylose and amylopectin, extracted from potato, was studied by surface tension measurements utilizing a drop volume technique. The results demonstrate that surface tension measurements have potential for characterising interactions between surfactants and the two starch polysaccharides amylose and amylopectin. The estimated binding of SDS to amylose was around 35 SDS molecules per 1000 glucosidic units measured on a 0.2% (w/w) amylose solution, and the binding curve indicates increased surface activity of the amylose-SDS system at high surfactant concentrations. The binding of SDS to amylopectin was more restricted, with a degree of binding of only 6-7 SDS molecules per 1000 glucose units when measured on 3 and 5% (w/w) amylopectin solutions. The binding curves of the SDS-amylopectin solutions with a low degree of binding support the view that some of the chains in the amylopectin molecule have the capacity to interact with the surfactant.