Acid modification of wheat, potato, and pea starch applying gentle conditions—impacts on starch properties

Abstract

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.

Alkaline dissolution of native potato starch − impact of the preparation conditions on the solution properties determined by means of SEC-MALS

“…The change of the chromatogram shape indicated in particular a higher amount of molecularly dispersed AP. The range of M w determined for native potato starch accords well with literature data found between 21 and 51 × 10 6 g/mol . However, significant higher values were also published (91 × 10 6 g/mol, potato starch , 114–117 × 10 6 g/mol, wild‐type potato starch ).…”

Impact of Process Parameters on the Acid Modification of Potato Starch

“…The acid modification was performed in slurry (40% w/w) under continuous stirring (400 min −1 ) according to the description elsewhere using HCl as acid. The reaction was stopped by adding NaOH dropwise until the desired pH between 5.4 and 6.0 was reached.…”

Properties of heated aqueous starch dispersions dependent on the preparation conditions

“…The protein, lipids, and ash contents were ≤0.1% w/w, ≤0.1% w/w, and ≤0.5% w/w, respectively (data provided by the supplier). The acid hydrolysis was performed using the slurry process according to the description by Ulbrich et al (40% w/w starch slurry containing 0.36 M (AT‐0.36 M HCl), 0.72 M (AT‐0.72 M HCl), and 1.08 M HCl (AT‐1.08 M HCl), respectively, hydrolysis at 40°C for 4 h, continuous stirring). The HCl (2 M, catalogue number T134.1) and NaOH (2 M, catalogue number T135.1) solutions for the starch modification were supplied by Carl Roth GmbH & Co. KG, Karlsruhe, Germany.…”