Extraction and characterization of starch from anchote (Coccinia abyssinica): physico-chemical, functional, morphological and crystalline properties

Starch is a polysaccharide that has an important role in food and other industries. Anchote, a local name for "Coccinia abyssinica" is an indigenous tuber crop to Ethiopia supposed to contain considerable amount of starch. This study aims to extract starch from this plant using sodium metabisulfite (0.025, 0.075 and 0.125% w/v), sodium chloride (0.5, 1.0 and 1.5 M) and water. Anchote starch extracted by using 0.075% (w/v) sodium metabisulfite has presented the highest extraction yield (75.56%) on a dry weight basis. The values of moisture content, bulk density and amylose content of anchote starch were recorded as 11.6%, 0.51 g/mL and 32.14%, repectively. The color of anchote starch was measured in L*, a*, b* values and obtained 89.80, 0.025, 3.63, respectively and whiteness was 89.16%. Its granular shapes exhibited polygonal, semi-oval with some round. The swelling power and the solubility of anchote starch were ranged from 2.15 to 10.6 g/g and 0.51-19.15% respectively. Syneresis of anchote starch increased when pastes were stored at low temperatures and decline in paste clarity upon storage. Anchote starch exhibited gelatinization temperature; onset, peak and conclusion (68.94, 74.99 and 84.87 degrees C) respectively. Pasting properties of anchote starch; peak, trough, breakdown, final and setback viscosities were recorded as 4879 cP, 2101.7 cP, 2777 cP, 5636.1 cP, 3535 cP, respectively. Anchote starch showed type B crystalline pattern with 39.15% relative crystallinity. FTIR spectra of anchote starch bands were almost similar with potato starch. The results indicate that this starch may be an alternative source for the production of industrial products that may require starch.