Small-angle X -Ray Scattering and Differential Scanning Calorimetry from Starch and Retrograded Starch

Abstract

Publisher Summary Although a regular periodicity has been observed in the native starch using Small-Angle X-ray Scattering (SAXS), this technique has not been applied to the retrograded material till now. This chapter presents a work that explores the retrogradation process of wheat starch by using SAXS and by extending the Differential Scanning Calorimetry (DSC) experiments. The results received from the two techniques in the work are compared in the chapter. The chapter concludes that the results explore the retrogradation of starch by relating information provided by DSC to data given by SAXS. The long-range configuration of retrograded starch is shown to differ from that of the native starch. Rates of re-crystallization as a function of storage temperature are reported and they are interpreted in terms of a picture of nucleation and growth of amylopectin crystallites. The retrogradation of starch is one of the major processes occurring during the staling of bread and other starch based products. DSC experiments performed on bread crumb yield similar results to those on starch gels. 30-33 Thus, information concerning the rates of re-crystallization of amylopectin in starch gels clearly has implications for the optimization of storage conditions for bread. Although storage in the refrigerator slows bacterial spoilage, the staling process under these conditions is dramatically accelerated. Similarly, frozen bread, once defrosted, stales at a faster rate than bread stored at room temperature.