Physical properties of pregelatinized and granular cold water swelling maize starches in presence of acetic acid

Pregelatinized (PG) and granular cold water swelling (GCWS) starches are physically modified starches which are used to enhance viscosity at ambient temperature. The main aim of this research was to determine the physical changes of these starches in the presence of acetic acid (0, 500, 1000 and 10,000mg/kg) as a common organic acid in foods. Native maize starch was converted to PG and GCWS starches using a twin drum drier and alcoholic-alkaline method, respectively. Scanning electron micrographs showed an increase in the size and central hole of the granules in GCWS starch and surface wrinkling of PG starch with increasing acid concentration. Water solubility increased, while water absorption, cold-water viscosity (as measured by a Rapid Visco Analyzer) and freeze-thaw stability of the samples reduced. A reduction in the paste viscosity, consistency, firmness and cohesiveness was observed as assessed using a Texture Analyser. Acetic acid increased the turbidity of GCWS starch but reduced the turbidity of PG starch pastes. The freeze-thaw stability of both samples reduced with addition of acetic acid, which was more pronounced after the first freeze-thaw cycle. These changes were enhanced with increasing acetic acid concentration. The changes caused by the acetic acid to the physical properties of PG starch were more obvious than those with GCWS starch.