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Enzymatic and Acidic Hydrolysis of Cationized Waxy Maize Starch Granules

¹Department of Biochemistry and Pharmacy; Åbo Akademi University, BioCity, P.O. Box 66, FIN-20521 Turku, Finland. ²Raisio Chemicals Oy, P.O. Box 101, FIN-21201 Raisio, Finland. ³Corresponding author: Fax: +358-2-2154745. E-mail: eric.bertoft@abo.fi

A series of wet-cationized starch granules from waxy maize with different degrees of substitution (DS) were solubilized with either 2.2M HCl (lintnerization) or with the α-amylase of Bacillus amyloliquefaciens. The maximum rate of the enzymatic hydrolysis occurred in starches with intermediate DS. It appeared that the cationic substituents interfered with the binding to the active site of the enzyme at high levels of substitution. The DS remained fairly constant in the granular residues after the enzymatic attack. The rate of the acidic hydrolysis increased with increasing DS but the final level of solubilization slightly decreased. The DS of the residual starch material decreased to 40% of the original level, showing that a large part of the cationic groups was found within the amorphous parts of the granules. A dry-cationized sample with a high DS was also treated with the acid and lost a major part of its substituents at low levels of lintnerization. Probably most of the substituents were associated with the surface and channels of these granules. The cationized starches possessed branches that were resistant to isoamylase attack and the samples also contained β-amylolysis resistant dextrins. The proportion of resistant dextrins in the granular residues decreased after lintnerization, but remained constant after the enzymatic hydrolysis.