Structural and physicochemical properties of enzymatically modified rice starch as influenced by the degree of enzyme treatment

The structure and physicochemical properties of rice starch modified with 4-alpha-glucanotransferase (4 alpha GTase) were compared for different enzyme treatment times (1, 24, and 96 h). Specifically, the gelation properties of native rice starch and 4 alpha GTase-treated rice starch (GS) were analyzed regarding their structural characteristics. The average molecular weight of GS decreased with increasing treatment time, and was 4.73 x 10(4) g/mol after 96 h of treatment. The chain length distribution was also broadened with the enzyme treatment, as 4 alpha GTase transferred alpha-glucan from one chain to another. The enzyme treatment also altered the gelation properties and decreased the viscosity of the starch depending on the treatment time, perhaps due to the changes in molecular weight distribution and branched chain length distribution. Moreover, the overall characteristics of GS differed significantly from those of maltodextrin. The physicochemical characteristics of GS with different degrees of 4 alpha GTase treatment suggest that it can be used in the food and pharmaceutical industries. [GRAPHICS]