Effect of iodine on polymer leaching and granule swelling of starches from different botanical sources

Iodine complexation with linear glucan polymers in starch granules is a function of the length of the available polymers and their arrangement within starch granules. In previous studies, this complex formation between iodine and glucan polymers has been shown to alter the pasting properties of starches from different botanical origins. In this study, the effect of iodine on the swelling capacities of corn (CS), wheat (WS), potato (PS) and tapioca (TS) starches was investigated by heating 8% starch slurry with different levels of iodine in a Rapid Visco Analyser (RVA). Increasing concentrations of iodine had an inverse effect on the swelling capacities of starches even though the granules were highly swollen, as observed in the micrographs. Furthermore, the composition of the leachate was different for the starches, suggesting that the swelling capacity was influenced largely by an increase or decrease in the amount of leachate and the absorption spectra of the leachate. The same amounts of iodine resulted in widely different swelling capacity values for the different starches, likely, suggesting differences in their granular architecture.

► Effect of iodine on swelling of corn, wheat, potato and tapioca starches.
► Increasing concentration of iodine inhibited granule swelling and polymer leaching.
► Same iodine volume resulted in dissimilar patterns of swelling in different starches.
► Granular architecture difference reflected by composition differences of leachate.