Abstract:

The waxy cornstarch，the normal cornstarch,the potato starch and the tapioca starch were gelatinizedand were then hydrolyzed by using β-amylase,and the hydrolyzates were investigated in terms of the fluidity,thedextrose equivalent ( DE) value，the relative molecular mass distribution,and the thermodynamic property. The resultsshow that ( 1) at the β-amylase dosage of 0.1%，the waxy corn-starch possesses the largest fluidity,while thenormal corn starch possesses the lowest fluidity; ( 2) at the β-amylase dosage of 0.3%,the fluidity of the hydrolyzatesafter a 5 h reaction become stable; ( 3) when the β-amylase dosage is more than 0.3%，the DE values of thehydrolyzates from cereal starches ( i.e. the waxy corn-starch and the normal corn-starch) is greater than those oftube starches( i.e. the potato starch and the tapioca starch) ; ( 4) the relative molecular masses of the hydrolyzatesfrom cereal starches exhibit a narrow distribution,while the relative molecular masses of the hydrolyzates of tubestarches are significantly different and are higher than those of cereal starches; and ( 5) the hydrolyzates of the normalcorn starch show the absorption peaks of the retrograded amylose or the starch-lipid complexes,while thehydrolyzates of the other three starches exhibit no absorption peak.

Key words: β-amylase, hydrolysis, fluidity, dextrose equivalent value, thermodynamic property