Microwave-assisted synthesis of zinc derivatives of potato starch

Zincatated potato starch was prepared in a solid-state, microwave-assisted reaction using generated in situ sodium tetrahydroxozincate [Na2Zn(OH)4]. For comparison, zincatation of starch was also carried out on convectional heating. Depending on the irradiation conditions, the products of either mono- or crosslinking esterification were formed. Higher power applied at shorter exposition offered products of monoesterification, and the lower power at longer exposition favoured crosslinking of starch. The microwave-assisted processes were faster than these proceeding on convectional heating. The reaction time was reduced from 120 to 30 min. The crystallinity of resulting products gradually ceased with increased concentration of introduced zincate but their granularity was retained independently of that concentration. The thermal stability of the products was slightly lower than that of native starch. Already reaction product prepared with the smallest dose of zincate had significantly decreased melting temperature and melting enthalpy and, simultaneously, increased aqueous solubility as well as water binding capacity compared to non-processed starch.