EFFECTS OF VARYING CONDITIONS OF ACID HYDROLYSIS ON SOME PHYSICOCHEMICAL PROPERTIES OF IPOMOEA BATATAS STARCH

Acid hydrolysis has been shown to be one of the methods of improving the functional properties of native starch. Starch was extracted from sweet potato tubers and hydrolyzed. The microcrystalline starch (MCS) was produced using 6 N HCl at varying temperatures (48 and 54 O C) and exposure times (6 - 24 hr). The physicochemical properties namely :- organoleptic properties, pH, solubility, hydration and swelling capacities, moisture sorption capacity, % moisture loss, particle size analysis, angle of repose, flow rate, true density, bulk and tapped densities, Carr’s index and Hausner’s ratio of the native and microcrystalline starches were evaluated. The results showed that at 48 0 C and exposure time of 12 hr, the highest yield (97.22 %) of MCS was obtained. However, hydrolysis at 54 0 C and exposure time of 6 hr gave the best material with excellent flow (angle of repose 27.23 0 and flow rate 20.6 g/s); Carr’s index and Hausner’s ratio of 16.4 % and 1.2 respectively; and hydration and swelling capacities of 2.36 and 1.7 respectively. The study has shown that the physicochemical properties of microcrystalline starch obtained from Ipomoea batatas were better than those of the native starch; and the optimum hydrolyzing conditions were 54 O C temperature and exposure time of 6 hr.