Optimization of starch isolation process for sweet potato and characterization of the prepared starch

Abstract

The study was conducted to standardize the parameters of centrifugation method of starch isolation for sweet potato to yield better quality starch. The effects of solid-to-solvent ratio in slurry-making, numbers of blending, slurry filtration and starch washings were studied for obtaining maximum yield and purity of starch with desired color and amylose content. The goal of the study was to develop a suitable process for small scale/on-farm processing of sweet potato for preparation of starch. A widely grown pink-skinned cream fleshed cultivar (Kanjangad) was used for the experiments. The studied parameters were slurry making solid-to-solvent ratio (1:2, 1:3 and 1:4), number of blendings (1 and 2 times), number of slurry filtration water washings (2, 3 and 4 times) and starch washings (2, 3 and 4 times). The study showed that the starch yield, purity, color and amylose were influenced by altering the starch isolation procedures. The solid-to-solvent ratio of 1:2 in the starch isolation process yielded the best results. Also, the increase in number of blendings degraded the purity, amylose and color of starch. The optimal process was slurry making at 1:2 solid-to-solvent ratio and once blending, slurry filtration washing for 2 times and starch washing for 2 times. Accordingly, the starch yield, purity, amylose, and L, a and b values were 13.967 ± 1.135%, 80.640 ± 1.139%, 29.220 ± 0.759%, and 57.88 ± 2.982, 0.386 ± 0.204, and 2.68 ± 0.127, respectively. The prepared starch was characterized for chemical composition, water activity, paste clarity, swelling power, water solubility index, pasting property and granule size and morphology. The study suggested that the prepared starch was suitable for food uses.