The extent of maize starch crystal melting as a critical factor in the isolation of amylose via aqueous leaching

Aqueous leaching from granular maize starch is a common technique for amylose (AM) isolation. Leaching was studied in a 60-90 degrees C temperature range. The leachate yield, degree of polymerization (DP) and purity were related to the extent of melting of the starch crystals at the leaching temperature as determined via differential scanning calorimetry. Annealing increases the amylopectin (AP) crystal stability and hence the remaining crystallinity at a given leaching temperature. Negligible AM leaching occurred at temperatures below the annealing dependent onset of melting. Leaching thus benefits from partial melting. Properties of AM leachates remained constant when the extent of starch melting remained below 80%. Loss of more than 95% of the melting enthalpy resulted in higher leachate DP at the expense of purity. As the crystallinity of annealed starches at a given leaching temperature was higher than for native starches, the leachate purity was higher. Although in no cases residual AP crystals remained at 90 degrees C, annealed starches yielded more pure AM extracts in higher yields than did native starch. More effective leaching in this case may be due to annealing- induced strengthened AP-AP interactions and AM disentanglement from AP. (C) 2016 Elsevier Ltd. All rights reserved.