Molecular and Supra-Molecular Structural Ordering of Wheat Starch-OSA Modified Waxy Maize Starch Mixtures During Storage

Abstract

The influence of waxy maize OSA starches on the retrogradation kinetics of wheat starch pastes is investigated using dynamic oscillatory rheological and differential scanning calorimetry (DSC) measurements. Total starch concentration for the rheological experiments is 4% (w/w) and wheat starch/OSA starch ratios are 100/0, 90/10, and 80/20. A modified fractional Kelvin-Voigt model is proposed to interpret system behavior under low oscillatory shear conditions and get deeper insight into its structural changes during storage. The results indicate that structural ordering of the systems composed of wheat starch and a) non-physically modified (OSA-ST); b) pregelatinized (Pregel OSA-ST); and c) hydrolyzed/spray dried (Hydrol OSA-ST) starches is governed by different molecular mechanisms. OSA-ST retarded short-term aging (7 days) of wheat starch gel due to amylose dilution with partially disrupted OSA-ST granules as well as the steric effect of OS groups. However, enthalpies of wheat starch/OSA-ST mixtures stored for 14 days were similar to that of wheat starch alone. On the contrary, both the rheological and DSC results suggest that mixtures containing Pregel OSA-ST and Hydrol OSA-ST retrograde slower than wheat starch gel during short and long storage. The model systems investigated in this study may represent a useful tool to understand the functionality of OSA starches as anti-staling additives in breadmaking.