Hydrothermal Modifications of Granular Starch, with Retention of the Granular Structure: A Review

Annealing and heat−moisture treatment are two hydrothermal treatments that modify the physicochemical properties of starch, without destroying granular structure. They involve incubation of starch granules in excess water/intermediate water content (annealing) or at low moisture levels (heat−moisture treatment) during a certain period of time, at a temperature above the glass transition temperaturr but below the gelatinization temperature. The impact of hydrothermal treatments on starch physicochemical properties is extensively discussed. Such physicochemical properties include granule morphology and crystallinity, double-helix content, amount and appearance of amylose−lipid complexes, gelatinization and pasting, swelling power and solubility, gel properties, and susceptibilities to acid and enzymic hydrolysis. Finally, the major differences between the effects of annealing and heat−moisture treatment are pointed out and an overview is given of possible explanations for the observed effects of hydrothermal treatments. Keywords: Starch; hydrothermal modification; annealing; heat−moisture treatment