Comparison of Functional Properties between Native and Chemically Modified Starches from Acha ( Digitaria Stapf) Grains

Abstract

Acha grain (Digitariaexilis)\rstarch was isolated and subjected to chemical modifications by acetylation,\rbenzylation, succinylation, carboxymethylation and acid-thining. Functional\rproperties (swelling, solubility, gelation, oil and water absorption capacities,\ralkaline water retention) and rheological properties of the native and modified\rstarches were determined. Swelling power and solubility of the starch samples\rincreased with increase in temperature. Swelling power and solubility were pH\rdependent, with maximum values obtained at pH 12 in both native and modified\rstarches. Increasing degree of alkalinity increased both solubility and\rswelling capacity. Water absorption capacities of chemically modified starches\rdecreased, but acetylated starch, ATAS showed higher value compared to the\rnative and also chemically modified starches improved oil absorption capacity\rof the native starch. The modified starches showed increase in alkaline water\rretention. Gelation studies revealed that ACAS had higher LGC than the native\rwhile some chemically modified starches did not alter the gelation capacity of the\rnative starch except for BAS and ACAS with LGC of 10% and 16% v/w. There were\rsignificant differences in functional properties between native and chemically\rmodified starches from acha, so chemical modification improved functional\rproperties. Chemical modifications increased pasting temperature except for\rATAS and BAS. Set-back values were reduced after modifications, indicating that\rmodification would minimize starch retrogradation.