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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. [ABSTRACT FROM AUTHOR]

Acid-thinned wheat, potato, and pea starch products were systematically prepared applying gentle conditions with variation of acid type (HCl and H2SO4), acid concentration (0.36 and 0.72 N in a 40% (w/w) suspension) as well as hydrolysis time (4 and 24 h). Starch granule properties as well as molecular and rheological characteristics in the solution state were analyzed and the impact of all parameters varied was found to be immense. Carbohydrate solubilization of wheat and potato starch was significantly higher compared to pea starch. Noteworthy progress in solubilization was found when hydrolyzed with HCl, and with increasing acid concentration and increasing hydrolysis time by trend. The hydrolysis affected the reduction of the hot paste viscosity most dominant in the first period of treatment (0-4 h), however, size exclusion chromatography-multi angle laser light scattering (SEC-MALS) analysis revealed a more prominent molecular degradation during the second period (4-24 h). This observation led to the interpretation that the molecular degradation in the initial phase results particularly in 'debranching' of the high molar mass amylopectin fraction and lower hot paste viscosity. Continued hydrolysis with significant reduction of the molecular size, however, had reduced impact on further lowering of viscosity. SEM micrographs displayed intact pea starch granules with unchanged surface after hydrolysis, whereas wheat and potato starch granules were visibly affected with damage not evenly distributed but a variation over the granule population. Granular wheat and potato starch exhibited significantly enhanced particle size after short period modification measured in water. However, this was found eliminated at extended hydrolysis time. Reasons were hydrolysis induced molecular rearrangement resulting in better crystalline packing on the amorphous/crystalline threshold reducing the ability to swell, and the progress in granular erosion. That was in line with changed swelling characteristics determined using DSC. The study gave evidence for strong impact of acid hydrolysis on functional properties like water binding. [ABSTRACT FROM AUTHOR]

A matrix of 27 acid‐thinned (AT) potato starch (PS) samples is prepared in a laboratory scale in slurry by gradation of the process parameters temperature (30, 40, and 50 °C), acid concentration (0.3, 0.6, and 0.9 m HCl) and time (4, 10, and 20 h), and is investigated in terms of functional properties (range of molar mass [Mw] between 17.7 × 106 and 1.95 × 104 g mol−1). The solubility (S) increased basically with a higher degree of molecular degradation and disintegration temperature, and the viscosity decreased systematically with decreasing Mw and increasing disintegration temperature. The existence of a specific Mw range of the starch to achieve highest gel strength is proved. However, an impact of the molecular properties on the light transmittance (Tgel) can be excluded, since all starch gels are opaque. A correlation between the strength and the specific non‐freezable bound water content (wnf) of the gels is found. High gel strength is accompanied by comparatively low wnf. In particular, the viscosity (processing) and the gel strength (final product characteristic), which are important technofunctional properties for the industrial application of AT starches, are found to be directly correlated to the Mw of the starch product. Moreover, the latter is controllable by the hydrolysis process parameters. [ABSTRACT FROM AUTHOR]