Extraction of starch and enzymatic production of high amylose starch from sweetpotato (Ipomea batatas) var. Telong

Starch from sweetpotato var. Telong was extracted at different ratios of sweetpotato and water. A 1:4 ratio (sweetpotato to water) was found to be optimum with 61% of the starch extracted. Further extraction (three times) of the residue at the same ratio of sweetpotato to water resulted in 98% of the total starch extracted. A high amylose starch was produced by debranching the amylopectin of the sweetpotato starch using 0.5% (v/dry weight) pullulanase (Promozyme D2) at 60 °C for 24 h. The effects of pH, temperature, substrate concentration and reaction time on the production of high amylose starch were studied. The optimum conditions for the production of high amylose starch were at pH 5.0, 5.0% (w/v) starch concentration and incubated at 60 °C for 8 h. The amylose content increased from 21 – 84% after 8 h of incubation. The surface morphology of the starch granules observed with a scanning electron microscope (SEM) showed shrinkage on the surface of the starch granules