Structural Processes during Starch Granule Hydration by Synchrotron Radiation Microdiffraction

Abstract

Starch granule hydration has been examined on the level of a single potato starch granule by static and dynamic synchrotron radiation (SR) microdiffraction techniques. A cryofrozen, hydrated granule was mapped through a 5 microm SR-beam in order to investigate its internal organization. The edge of the granule showed fiber texture scattering due to radially oriented amylopectin helices. The variation of fiber texture across the granule center supports the model of concentric shells. The crystalline phase appears, however, to increase strongly toward the granule center due to a random amylopectin fraction, which could be related to crystallization of short-range ordered amylopectin during hydration. During gelatinization, the shell structure breaks down and remaining fiber-textured amylopectin domains belong probably to the swollen starch granule envelope. Hydration of a granule was initiated by a microdrop generator and followed in situ by SR-microdiffraction. A fast hydration process with a half time of about 7 s seems to reflect the porous nature of starch granules. The size of the hydrated domains suggests that this process is limited to the level of amylopectin side chain clusters. Longer hydration times are assumed to involve remaining short-range ordered amylopectin and results in larger domains.

Morphological and structural aspects of the giant starch granules from Phajus grandifolius

“…The SR microdiVraction experiments reported in Figs. 8-10 indicate that the beam damage on the granules of P. grandifolius is comparable to that observed in potato starch (Lemke et al, 2004). Again, it is seen that the use of liquid nitrogen is determinant to, not only extend the "life" of the starch granules in the X-ray beam, but also to preserve the quality of the X-ray diVraction patterns.…”

“…Following this pioneer work, the recent advent of synchrotron radiation (SR) machines and the development of the microfocus beamline at ESRF, Grenoble, France (Riekel, 2000) have greatly improved the microdiVraction method. The technique has now been applied to a number of starch granules from B and C family (Buléon et al, 1997;Buléon et al, 1998;Lemke et al, 2004;Riekel et al, 2004;Waigh et al, 1997). X-ray probes with a diameter as low as 0.5 m are currently available, with the brilliance of the synchrotron and 0.1 m probes will be available in the near future.…”

Physical properties of fats in food

“…This was the first study involving the structural analysis of the texture of fat crystals using an X-ray microbeam method. Before this work, there had been no study using SR-μ-XRD in the research area of food science except for the study of the microstructure of starch (Buleon et al, 1997;Chanzy et al, 2006;Lemke et al, 2004).…”

Applications of synchrotron radiation micro-focus techniques to the study of polymer and biopolymer fibers

“…These developments will find applications in micro-fluidic devices in particular. Thus, hydration by inkjet printing systems has been demonstrated for fibrous biopolymers, such as h-chitin [46] or starch [47,48], and can be easily extended to fibers. Such local hydrations can result in micro-reaction zones, which are accessible to A-XRD.…”