Physicochemical, thermal, structural and pasting properties of unconventional starches from ginger (Zingiber officinale) and White Yam (Dioscorea sp.)

Abstract

Ginger and white yam starches were investigated and compared with maize starch. Proximal composition, thermogravimetry, differential scanning calorimetry, microscopy, colourimetry, X-ray powder diffractometry and pasting profile were analysed. The unconventional starches presented higher protein and ash contents than the maize starch, that had the highest thermal stability. Higher gelatinisation temperatures were reported for ginger starch, and the enthalpy of the unconventional starches were similar. The maize starch presented the lowest gelatinisation values. For the corn starch the granules were polygonal and smaller than the unconventional starches, and oval shapes and larger diameters were found for the ginger and yam starches. The unconventional starches presented less brightness and a greater tendency to red and yellow. The maize and ginger starches had A-type diffraction patterns, while the white yam starch had a C-type pattern. The highest relative crystallinity was observed for the ginger starch and there were small differences between the yam and maize starches. Higher peak viscosity and final viscosity and lower pasting temperature were observed for the yam starch. Ginger starch showed the highest shear and stability of heating glue, so may be used in products processed under high temperatures; and yam starch can be used in acidic foods that require high viscosities.