Abstract:
Starch was isolated from cereals (rice, waxy rice, sorghum, ragi and wheat) pulses (chick pea, green gram), root (tapioca), tuber (potato) and were single acid (0.5N HCl) modified for different periods, also modified with 0.5N of each of HNO3, H2SO4 and H3PO4 for 1.5h. AFN increased progressively with time of modification and was highest for cereals followed by root, legume and tuber starches. However, reduction in Mn was in the reverse order. There was a clear proportionality between Mn of native starches and the extent of its hydrolysis under any given set of conditions. Modified starches without neutralization kept in RT continue to hydrolyze strongly in potato starch compared to other starches. Highest AFN for HCl and HNO3 was observed followed by H2SO4 and H3PO4. Extent of hydrolysis was proportional to Mn of native starches observed only in HCl and HNO3 but not in any other acids. [n] of native starches showed positive correlation with their Mn and decreased upon modification. IBC did not follow any pattern. Mn and IBC of solubilized starches were lower in all modified starches except potato which did not change much. GPC of native starches using Sepharose CL4B gave mainly two fractions, Frn I (high molecular weight) and Frn II (low molecular weight). After acid modification, Frn II increased and Frn I decreased. Very high increase in Carbohydrate content in Frn II was seen in Cereal Starches followed by pulses, root and least by tuber. Work on Alpha amylase enzyme hydrolysis in comparison with 0.5N HCl hydrolysis in non-granular starches, C13 CP/MAS spectroscopic studies of these starches will also be presented.
Some Symbols: AFN: Alkali Fluidity Number; Mn: Number Average Molecular weight; [n]: Intrinsic viscosity; IBC: Iodine Binding Capacity
