OXIDATION OF POTATO STARCH BY HYDROGEN-PEROXIDE

Potato starch was oxidized by hydrogen peroxide in alkaline and acidic reaction conditions with copper, iron and tungstate catalysts in orde r to introduce carboxyl and carbonyl groups to the starch molecule. Ca rbonyl contents up to 6.6 per 100 glucose units could be obtained, whe reas carboxyl content remained low (up to 1.4). Starch yields in the a lkaline and acidic reactions were 90 and 99%, respectively. The molecu lar weight decreased markedly with the degree of oxidation, and was de pendent on the catalyst used. Rheological measurements revealed that w hen the molecular weight of the moderately oxidized starch was high, a very firm gel (G' = 40kPa) was obtained with 25% starch concentration . When the degree of oxidation increased, the storage modulus G' decre ased. The more the oxidized starch contained carbonyl groups, the high er was the gelatinization temperature.