Pea Starch Annealing: New Insights

Three different pea starches were annealed in excess water at 45 °C for 24 and 72 h, and the changes in their structure and functionality were determined. Annealing resulted in slightly irreversible swelling with leaching of some amylose molecules, which was accompanied by small changes in granular morphology and relative crystallinity, but significant changes in functionality such as decreased swelling power and starch solubility and increased thermal transition temperatures, enthalpy changes, pasting viscosities and in vitro digestibility. Annealing led to an increase in proportion of B-type polymorphs within C-type pea starches, which was explained as being due to a polymorphic transition from A to B. Annealing mainly acts on the amorphous regions of starch granules, leading to amylose leaching. The removal of amylose molecules can reduce the long-range forces within the granule and thereby weakening the overall granule structure and leading to significant changes to functional properties. This study showed that annealing is a mild but important physical modification of starch, which can be used as a pretreatment technique to tailor the starch functionality for specific industrial application.