Preparation and Physicochemical Properties of Starch Spherulites
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Abstract:
In this study, waxy maize starch was used as the experimental raw material, and starch spherulites were prepared via isoamylase-catalyzed debranching and recrystallization. The effects of enzyme quantity and recrystallization time on the properties of starch spherulites were investigated though measuring the chain length distribution, branching degree, yield, morphology, crystallinity and thermodynamic properties. Results showed that the gelatinized waxy maize starch could be completely debranched by isoamylase (25 U/g) through adding the enzyme after being cooled to 50 ℃ followed by an incubation at 50 ℃ for 24 h. The average chain length of the obtained starch spherulites was 26.70. The debranched starch was recrystallized at 25 ℃ to form starch spherulites. The yield and crystallinity of starch spherulites increased with the crystallization time, which were 76.58% and 51.1%, respectively, after crystallization for 24 h. The onset gelatinization temperature (To), peak temperature (Tp), conclusion temperature (Tc) and enthalpy change (△H) of starch spherulites were higher than those for the original waxy maize starch, and these values increased with the crystallization time. The SEM images showed that the granules of starch spherulites and agglomeration of starch granules became obvious with the increase of crystallization time.
