Physicochemical properties of amylose-free starch from transgenic sweet potato

A transgenic amylose-free sweet potato has been obtained by introduction of granule-bound starch synthase I (GBSSI) cDNA of sweet potato in sense orientation (Plant Cell Reports (2001)). In this study, starches from 6 transgenic sweet potatoes produced by introduction of GBSSI cDNA, including the amylose-free transformant, were analyzed for their physicochemical properties, granule-size distribution, enzymatic digestibility, amylopectin structure, gelatinization properties and pasting properties. We observed little difference in granule size distribution between amylose-free starch and control starch. Amylose-free starch was more susceptible to glucoamylase digestion than control starch. The amylopectin of the amylose-free transformant was found to have a slightly lower content of short chains. Amylose-free starch showed higher gelatinization temperature and gelatinization enthalpy and lower setback in comparison with control starch. Thus, it was found that the starch from the amylose-free transgenic sweet potato possessed unique physicochemical properties.