The Role of Sequential Enzyme Treatments on Structural and Physicochemical Properties of Cassava Starch Granules

摘要

To illuminate the relationship between the branch chain structures and physicochemical characteristics of cassava starch and to expand the range of its functionality, cassava starch granules are modified with sequential alpha-amylase from hog pancreas, barley beta-amylase, and transglucosidase from Aspergillus niger. The molecular weight and amylose contents of the enzyme-modified starches decrease, and the modified starches exhibits increased numbers of short and medium chains and a higher branch density compared with those of control starch. The crystal pattern is transformed from A-type to a mixture of A-type and V-type, and the crystallinity is reduced. The enzyme-modified starches exhibits increased solubility and paste clarity, a more homogeneous crystal distribution, and reduced gelatinization temperatures, gelatinization enthalpy, and viscosity compared with those of control starch. The enzyme-treated starches exhibit a larger elasticity modulus, a viscous modulus, and a reduced loss angle tangent when the range of the transglucosidase treatment time is from 2 to 4 h, whereas the opposite effect is observed when the transglucosidase treatment time ranges from 8 to 10 h. These findings demonstrate that the rheological properties of the enzyme-modified starch are significantly dependent on the time of the transglucosidase treatment. Thus, triple enzyme modification may supply a new potential method to obtain the expected hydrophilic, rheological, and thermal properties of cassava starch.