Effect of annealing on the molecular structure and physicochemical properties of starches from different botanical origins – A review

Annealing is a hydrothermal treatment that changes the physicochemical properties of starches by improving crystalline perfection and by facilitating interactions between starch chains. The extent of these changes being influenced by starch composition and by the arrangement of the starch chains within the amorphous and crystalline domains of the native starch granules. During annealing, starch granules in excess or at intermediate water content are heated for a certain length of time, at a temperature above the glass transition but below the gelatinization temperature. This review summarizes the current knowledge on the effect of annealing on the granule morphology, composition, crystallinity, X-ray pattern, granular swelling, amylose leaching, pasting properties, gelatinization parameters, and acid and α-amylase hydrolysis of starches from cereals, legumes and tubers. The physical probes used in studying the mechanism of annealing, in-vivo annealing and the application of annealing in the food industry is also reviewed. Recommendations for future research is outlined.