EXTRACTION OF STARCHES FROM TUBER CROPS USING AMMONIA

Ammonia solution (0.03 M) was used to extract starch from various tuber crops by the conventional settling method. It was found that there was noticeable improvement in the yield of starch from Colocasia (6-16%), while it fell for sweet potato starch and remained almost the same for the other starches. The various properties of starch, thus extracted, were compared with those for starch obtained by water extraction. It was found that total amylose of all starches were unaffected while the 'soluble amylose' was slightly suppressed for Colocasia starch extracted with ammonia solution. Peak viscosity was found to be increased to a large extent for Colocasia and Dioscorea esculenta starches by ammonia extraction, while it was lowered for sweet potato starch. The swelling volume of Colocasia starch extracted with ammonia was similarly enhanced by 25%, but the Dioscorea esculenta starch did not show such a tendency. Sweet Potato starch suffered a reduction in swelling volume. Phosphorus content was found to be independent of the extraction medium.