The debranching enzyme pullulanase (PUL) is used in order to conduct a partial conversion of a regular granular potato starch (PS) improving the techno‐functional properties when used as a gelling agent. The starch is hydrolyzed systematically by grading the amount of a technical enzyme solution added (1, 2, 3, 4, 5, 10, 20, and 40 mL PUL solution) resulting 400 g of a 20% (w/w) suspension. Morphological characteristics of the granules (scanning electron microscopy, SEM), swelling behavior (differential scanning calorimetry, DSC), polymer solubility, hot paste viscosity, gel strength, and molecular properties of the starch samples (size exclusion chromatography‐multi angle laser light scattering‐differential refractive index detection, SEC‐MALS‐DRI) as well as the respective separated amylose (AM) and amylopectin (AP; size exclusion chromatography‐conventional standard calibration‐differential refractive index detection, SEC‐cal‐DRI) branch chains fractions are comprehensively analyzed. The granule surface is visibly affected, but the granular structure is largely intact. The DSC gelatinization characteristics are impacted manifold, and the solubility, in particular when disintegrated using pressure cooking, increases. The hot paste viscosity decreases, while the ability to form mechanically stable gel structures increases due to modification. The weight‐average molar mass (Mw) decreases from 38.2 × 106 (native) to 2.3 × 106 g mol−1 (40 mL PUL solution), in particular due to cleavage of α‐1,6‐linkages within the AP. Surprisingly, the detailed analysis reveals a concomitant and remarkable degradation of the AM‐fraction. The partial hydrolysis of granular starch by means of a debranching enzyme is shown to be basically a very specific, fast, and serious alternative to e.g., the acid‐tinning process.

Potato starch (PS) is enzymatically modified using α‐amylase and comprehensively characterized. Modified PS is prepared by adding different amounts of α‐amylase (0.04, 0.08, 0.16, and 0.33 mL of an enzyme solution (LpHera, Novozymes A/S) to 400 g of a 40% w/v aqueous starch suspension and reacting for 15 min at 40 °C. Morphological characteristics (SEM), pasting (viscosity profile, thermal behavior‐DSC) and molecular properties (SEC‐MALS‐DRI), carbohydrates solubility, hot paste shear viscosity, and gel strength are analyzed. The morphological characteristics are significantly affected by the α‐amylase. The surface of the granules shows small cracks and holes. In regard to the characteristic pasting parameters, there are significantly decreased values after hydrolysis. However, the DSC gelatinization properties are slightly impacted by the modification. The solubility of the starch polymers is increased by the increase of both the enzyme dosage and the disintegration temperature applied (95 and 145 °C). Moreover, the molecular composition of the solubilized starch is impacted, too. The investigation of molecular dispersed solutions demonstrates the strong degradation of both amylose (AM) and amylopectin (AP). An increasing enzyme concentration led to a systematically decreased Mw in the samples. The degradation within the amorphous areas is presumed to be faster, similar to acid hydrolysis in native granular starch. However, gelation properties of the enzymatically modified starches are not perceptible. The gradual depolymerization effected the reduction of the hot paste viscosity accordingly.

Granular potato starch is modified using the debranching enzyme isoamylase. The modification is performed in aqueous suspension (40% w/w) at 35 °C by grading the volume (100, 250, and 400 µL/50 g of starch, 200 U · mL−1) of enzyme solution added. The starch products obtained are comprehensively investigated in terms of morphological (scanning electron microscopy), structural (X‐ray diffraction), thermal (differential scanning calorimetry), techno‐functional (solubility, hot paste viscosity, gel strength), and molecular properties (size exclusion chromatography‐multi angle laser light scattering‐differential refractive index detection). The granular integrity is basically preserved after modification and a molecular degradation predominantly of the amylopectin by debranching is proved. However, a slight reduction of the weight average molar mass of the amylose fraction is found too. In addition, the intended partial molecular degradation of the starch polysaccharides, the effect of the preparation procedure including washing with ethanol and grinding impacts several starch characteristics conspicuously.

Abbreviations: ANOVA, analysis of variance; DRI, differential refractive index; FTC, multiple freezing-thawing cycle; M w , weight-average molar mass; PFTC, pre-swelling multiple freezing-thawing cycle; PS, potato starch; SEC-MALS-DRI, size exclusion chromatography-multi-angle laser light scattering-differential refractive index detection; TA, texture analyzer; T c , conclusion temperature; T o , onset temperature; T p , peak temperature; ΔH gel , swelling enthalpy; ΔT gel , the gelatinization range.