Hydrothermal treatments of Finger millet ( Eleusine coracana) starch

Abstract

The effect of hydrothermal treatments on the properties of Finger millet starch was investigated. Finger millet was modified by heat-moisture treatment, HMT at 100 °C, 16 h; 20% moisture level (MHT-20), 25% moisture level (MHT-25) and 30% moisture level (MHT-30) and annealed, ANN at 50 °C for 48 h (MAN). Results of the pasting characteristics shows that MNS and MAN were indicative of type ‘B’ starch which is characteristic of normal cereal starches, while HMT starches were Type ‘C’ which is characteristics of cross-linked or legume starches. MNS belonged to the type ‘A’ pattern of cereal starches. X-ray diffractometry studies (XRD) show that MNS gave strong peaks centered at 23.5, 20.3, 18.2, 17.15, and 15.15 Å, while HMT and ANN starches retained the typical ‘A’ pattern. Scanning electron microscopy (SEM) studies show that the shape and surface characteristics of the starches were irregular, polygonal-shaped granules, with less than 1% cavity or ruptured granules. Modification did not affect the appearance. All the starches swell as the temperature increased in the order MNS>MAN>MHT-20>MHT-25>MHT-30, and solubilized at different rate in the following order: MHT-30>MHT-20>MHT-25>MAN>MNS. The gelation profile of the starches ranged from 4 to 8% (w/v), while its oil and water absorption capacity ranged from 1.90 to 2.50 and 2.75 to 3.25 g/g, respectively.