The effect of long-term alkali treatment on the molecular characteristics of native and extruded starches at 35°C


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In this study the molecular characteristics of native and extruded starches of wheat, corn, and potato were observed under long-term alkali treatment (0.5 M NaOH, 7 days, 35°C). The molar mass distribution of samples determined by means of calibrated semi-analytical size exclusion chromatography (SEC) showed different profiles (double and single peak distribution) depending on the dissolution status of the starch polysaccharides with simultaneous loss of supermolecular structures because of disintegration of the aggregates. The molecular range was between 4 × 103 and 2 × 106 g/mol and their calculated average molar masses were Mw = 1.7 × 105–4.1 × 105 and Mn = 2.5 × 104–1.1 × 105 g/mol. The reduction value and the value of intrinsic viscosity were additional indicators for the dissolving status of starch polysaccharides as well as for the stability of starch molecules in alkaline solution.