Chapter 9 - Developments in the Application of Small-angle Neutron Scattering to Food Systems

Abstract

This chapter describes the application of small-angle neutron scattering (SANS) to food systems for obtaining information on intra- and inter-particle structure, on a length scale of typically 10-1000 A. SANS and SAXS (small-angle X-ray scattering) are similar techniques in principle, and complementary in practice. Both are able to study systems in their native, solution state. However, SANS has some advantages for food and colloidal systems. The largest wavelengths usable for SANS and SAXS are >10 A and about 1.5, respectively. The longer wavelength of SANS makes it more effective than SAXS for the study of the large-scale colloidal structures found in food systems. As neutron scattering experiments use central facilities, they require a strong justification. For food systems, the justification can be that the system is of great economic or nutritional significance in itself, or the results will be of significance for a wide range of food systems. SANS is most effective on systems that are monodisperse or have a monodisperse feature, the size of which can be measured by SANS. The subunits of uniform size and the surface layers of uniform thickness are the examples of such features. If samples do not contain such monodisperse features, then useful information can be derived by comparing samples before and after processing. The “contrast variation” method gives the ability to “highlight” or “blank out” the different phases of a multi-phase system and adds greatly to the power of SANS.