Effect of heat moisture treatment on the functional and tabletting properties of corn starch

The effect of heat moisture treatment on the functional and tabletting properties of corn starch BP was investigated. Corn starch was hydrothermally modified by heat moisture treatment (HMT) at 100 degrees C, 16 h; 20% moisture level (HIC - 20), 25% moisture level (HIC - 25), and 30% moisture level (HIC - 30). The tablet formation properties were investigated using Heckel and Kawakita equation, while its tabletting properties were assessed using tensile strength, crushing strength, friability and disintegration time. The results reveal that HMT reduces the gelatinisation temperature and pasting properties of the corn starch. However, all the starches swell as the temperature is increased, HMT of the corn starch lowered the swelling power of the starch, while the solubility profile increased. The X-ray diffractometry study reveal that the native and HMT starches maintained the characteristic 'A' diffraction pattern of the cereal starch with strong peaks at 15.35, 17.15, 18.2 and 23.55 angstrom. The bulk density of the starch was in the order: HIC-30 approximate to HIC-25 > HIC-20 > NaIC, with reduction in the Carr's index, compressibility index, and Hausner's ratio after HMT treatment. The mean yield pressure, P-y, (from Heckel analysis) which is inversely related to the ability of the materials to deform plastically under pressure, was relatively high after HMT of the corn starch. Also, the P-k values (from Kawakita analysis), which is related to the deformability of the individual powder increased after HMT of the corn starch compacts in the following order: NaIC << HIC-20 < HIC-25 < HIC-30. The tabletting properties studied reveal a reduction in the crushing strength and tensile strength after HMT of the corn starch compacts. However, the friability of the starches increased while there was reduction in the disintegration time of the corn starch compacts after HMT. Thus, HMT of corn starch could be useful when fast disintegration, lower swelling power, and lower crushing strength are desired in tablet.