Abstract:

A series of porous starches with similar hydrolysis rates were prepared by controlling the hydrolysis timeand the enzyme dosage.The influences of the hydrolysis time and the enzyme dosage on the aggregation structure ofstarch granules were investigated by means of SEM,DSC and the small angle X － ray scattering ( SAXS). Experimentalresults indicate that ( 1) at similar hydrolysis rates,starch granules with a shorter hydrolysis time and ahigher enzyme dosage are broken more significantly than those with a longer hydrolysis time and a lower enzymedosage,but the amorphous region and the inner part of the latter were hydrolyzed more seriously with a bigger cavityinside the granules; ( 2) the enthalpy of the starches decreases with the increase of the hydrolysis rate,and it decreasesmore obviously with the extension of the hydrolysis time at a higher hydrolysis rate; and ( 3) during the hydrolysis,the aggregation structures of starch granules change in the amorphous region and the semi － crystalline region;specifically,the hydrolysis time and the enzyme dosage mainly affects the semi － crystalline region and the amorphousregion,respectively.

Key words: starch, enzymatic hydrolysis, porous starch, aggregation structure