Specific Modification of Granular Potato Starch by Means of Partial Debranching Using Pullulanase

Abstract

Native potato starch (PS-N) is enzymatically modified in the granular state using pullulanase (PUL) for the purpose of a specific partial molecular degradation of the polymers. The PUL compound is added to the aqueous starch suspension (40%, w/w) and processed. The process parameters are varied systematically (enzyme dosage [ENZ] 4/20 mL; pH of the suspension [pH 4.7/7.3]; hydrolysis temperature [TEMP] 40/50 °C, and hydrolysis duration [TIME] 20/120 min) and a new-developed heat-induced enzyme inactivation approach (storage of the partially dewatered moist starch for 120 min at 100 °C) is intended to terminate the hydrolysis. Morphological (LM, SEM, and CLSM) and thermal characterization (DSC) of the starch products indicate a partial damage of the granules and a partial loss of the semicrystalline structure owing to the heat treatment, which is confirmed by XRD. The molecular properties (SEC-MALS-DRI) are mainly controlled by the factors ENZ, pH, and TEMP, but the intended degradation of the amylopectin (AP) by cleavage of the α-1,6-linkages (debranching) is accompanied by a molecular degradation of the amylose (AM) fraction. However, both specificity of the hydrolysis and achievable gel strength are remarkably improved compared to acid-thinned products.