Synthesis and characterisation of starch cuprate.

The cupration of granular potato starch with ammonium tetrachlorocuprate(II) was performed by a 20min lasting microwave-assisted process and by 40min convectional heating. In both cases the degree of esterification (DE) did not exceed 6.4×10(-3). A higher dose of cuprate had a positive effect on DE, regardless of whether the microwave irradiation or the convectional heating was applied, and on the thermal stability of the starch cuprate produced in the microwave-assisted way. As a result of cupration, the hydroxyl ligand of the starch d-glucose units was replaced by the chloride ligand of the tetrachlorocuprate(II) anion. In the starch cuprate formed in the microwave-assisted process, the cuprate anion additionally coordinated water molecules. The cupration reduced starch crystallinity, as indicated by X-ray diffractometry and differential scanning calorimetry.