INFLUENCE OF ANNEALING ON THE PASTING PROPERTIES OF STARCHES FROM VARYING BOTANICAL SOURCES

Pea, potato, wheat, and rice starches were annealed for 24 hr. Differe ntial scanning calorimetry data were collected; pasting characteristic s were determined using the Brabender Viscoamylograph and the Newport Scientific Rapid Visco-Analyser (RVA); and amylose leaching during hea ting in the viscoamylograph was examined. Differential scanning calori metry data showed an increased gelatinization temperature and enthalpy , and a narrower gelatinization temperature range for all starches. Vi scoamylograph viscosity curves showed that annealing resulted in an in creased peak viscosity (except for potato starch), and an increased vi scosity 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 solubiliz ed amylose was practically unchanged (slightly decreased) after the an nealing treatment for rice starch, whereas annealed wheat starch showe d 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), viscosit y 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 an nealed potato starch, the viscosity was decreased. A higher rigidity a nd increased resistance to heat and shear of the starch granules are p robably the main causes of the viscosity changes due to annealing, bot h in water and in a DMSO-water mixture.