Application of small-angle X-ray and neutron scattering techniques to the characterisation of starch structure: A review

Scattering methods offer the unique potential to indirectly probe materials on length scales between the capabilities of modern crystallography and microscopy, thus bridging the gap in spatial resolution between the two groups of techniques. The most significant achievement of small-angle scattering techniques in starch science has been the quantification of the lamellar architecture of semicrystalline growth rings in native starch granules. The lamellae are structurally formed by side chains of amylopectin interspersed with amylose and their behaviour upon contact with water and varying temperature has been explained using a widely accepted 'liquid crystalline' model for starch. Scattering techniques have also been recently used to explore the structural factors in native and processed starches that determine resistance to acid and enzymatic hydrolysis. Attempts have been made to apply scattering methods in understanding more complex structures in starch-based food products. Application of these techniques that are traditionally not widely used in food materials science provides fascinating challenges and opportunities. With more basic scientific methods entering food technology, it is apparent that small-angle scattering techniques deserve their place in the multi-technique approach, which aims to understand the structural mechanisms governing starch processing and digestion, and makes it possible to design and select those processes which render desirable structural morphologies. This paper summarises previous investigations and the current status of research into the structure of native starch and starch-based systems using small-angle scattering techniques.