Effect Of Chemical Modifications On Functional Properties Of Mung Bean(Vigna Radiata (L.) Wilczek) Starch

Starch from mung bean seeds was isolated and chemically modified through three types of modification namely oxidation, acetylation and succinylation. The functional, thermal and rheological properties of the modified mung bean starch were determined.The surface morphology of the native starch granules appeared with irregular shapes, which varied from oval to round to bean shape with smooth surface. Succinylation led to partial rupture of the granule integrity, acetylation had less effect in the granule integrity than succinylation, and oxidation converted the smooth surface of the native granules to a surface with fissures. Swelling capacity improved through esterification but was reduced after oxidation. Both acetylation and oxidation enhanced solubility, where as succinylation had no uniform effect throughout the temperature range. Oil absorption capacity was increased by oxidation and acetylation but reduced by succinylation. All types of modification increased hydrophilic tendency with decreased gelatinization temperature of native starch. Syneresis increased after oxidation but was decreased following esterification.All types of starches exhibited a non-Newtonian shear thinning flow behavior. As for the hot viscosity native starch showed the highest value followed by succinaylted, acetylated, and oxidized starch respectively. During cooling, the gel formation of oxidized starch revealed highest storage module followed by native starch, while succinaylted and acetylated starches exhibited the same storage module. However, the succinaylted starch displayed a slightly higher value of loss module and phase angle than acetylated starch; this signified that the later one form a stronger gel when compared with the former one. Furthermore mung bean starch acetate has been successfully produced with transesterification reaction between vinyl acetate (VAC) and hydroxyl groups (OH) of the starch under microwave assistance using potassium carbonate (K2CO3) as a catalyst. Varying amount of potassium carbonate (0.0-7.2mmol) was resulted in starch acetate with increased mood of the degree of substitution (0.003-0.27) in a very short time. Increasing in the peak intensity of ester carbonyl group(C=O) at1742following the increasing in the degree of substitution was further proved by Fourier transform infrared spectrophotometer. Obvious change in the starch granules morphology, Increasing in the hydrophilicity and decreasing in the temperature of gelatinization and enthalpy were noticed accordingly to the degree of modification. The X-ray pattern of native starch was A type, with similar pattern in modified derivatives.