Influence of Annealing on the Pasting Properties of Starches from Varying Botanical Sources

Pea, potato, wheat, and rice starches were annealed for 24 hr. Differential scanning calorimetry data were collected; pasting characteristics were determined using the Brabender Viscoamylograph and the Newport Scientific Rapid Visco-Analyser (RVA); and amylose leaching during heating in the viscoamylograph was examined. Differential scanning calorimetry data showed an increased gelatinization temperature and enthalpy, and a narrower gelatinization temperature range for all starches. Viscoamylograph viscosity curves showed that annealing resulted in an increased peak viscosity (except for potato starch), and an increased viscosity upon cooling. The amount of amylose leached from the granules was not linked to viscosity changes. Less amylose was leached from the granules of annealed pea and potato starches. The amount of solubilized amylose was practically unchanged (slightly decreased) after the annealing treatment for rice starch, whereas annealed wheat starch showed a slightly increased leaching of amylose. Except for pea starch, RVA results were comparable to the results from the viscoamylograph. In a dimethyl sulfoxide (DMSO) and water mixture (92.5:7.5, w/w), viscosity changes were not consistent for all annealed starches. For annealed pea, wheat, and rice starches, the onset of solubilization occurred at lower temperatures. The increased peak viscosity was attributed to a higher rigidity and resistance to shear of the starch granules. For annealed potato starch, the viscosity was decreased. A higher rigidity and increased resistance to heat and shear of the starch granules are probably the main causes of the viscosity changes due to annealing, both in water and in a DMSO-water mixture.status: publishe