Physicochemical, structural characterization and pasting properties of pre-gelatinized Neorautanenia mitis starch.

Background: Pre-gelatinization is one of the most common physical methods of starch modification, which involves heating to bring about significant changes in the nature of starch, such as high swelling, loss of crystallinity, solubility in cold water, and improved pasting.

Objectives: To evaluate the structural and physicochemical properties of starch from Neorautanenia mitis tubers, and determine the effect of pre-gelatinization on the functional properties of this starch.

Material and methods: Properties of the pre-gelatinized starch (NMPS), such as flow, swelling power, hydration capacity, pH, morphology, Fourier-infrared spectroscopy (FTIR), differential scanning calorimetry, and pasting characteristics, were compared with those of the native starch (NMNS).

Results: Pre-gelatinized starch had good flow with the angle of repose at 33.69°. Carr's index was 10.90% and 7.50%, and the Hausner ratio was 1.12 and 1.05 for NMNS and NMPS, respectively. Both starches had neutral to near-neutral pH (7.00 and 6.04, respectively). The hydration capacity of NMPS (59.00%) was about 2 times higher than that of NMNS (25.80%), while the swelling power of NMPS between 40°C and 60°C was higher than that of NMNS, and maximum swelling for both starches was observed at 80°C. Morphology showed that NMNS granules were discrete, smooth and spherical, while those of NMPS were aggregated, with rough surfaces. The FTIR spectra of both starches showed identical absorption peaks but the enthalpy of gelatinization differed for both starches. The pasting properties also varied significantly among the starch samples. Native starch had better peak viscosity, breakdown viscosity and pasting temperature, while NMPS presented better trough viscosity, final viscosity, setback viscosity, and pasting time.

Conclusions: The results showed that pre-gelatinized starch from N. mitis tubers possesses high swelling and hydration abilities and significant pasting properties, and may be used as a disintegrant in solid dosage formulations and in products requiring low viscosities and bond strength.